Programs & Examples On #Android

Android is Google's mobile operating system, used for programming or developing digital devices (Smartphones, Tablets, Automobiles, TVs, Wear, Glass, IoT). For topics related to Android, use Android-specific tags such as android-intent, not intent, android-activity, not activity, android-adapter, not adapter etc. For questions other than development or programming, but related to Android framework, use the link:

Android Canvas.drawText

Worked this out, turns out that is not the same as Color.BLACK. Changed the code to:

Paint paint = new Paint(); 

canvas.drawText("Some Text", 10, 25, paint); 

and it all works fine now!!

Prevent the keyboard from displaying on activity start

To expand upon the accepted answer by @Lucas:

Call this from your activity in one of the early life cycle events:


Kotlin Example:

override fun onResume() {


WebView and HTML5 <video>

I know this is an very old question, but have you tried the hardwareAccelerated="true" manifest flag for your application or activity?

With this set, it seems to work without any WebChromeClient modification (which I would expect from an DOM-Element.)

How to set a timer in android

I used to use (Timer, TimerTask) as well as Handler to kick off (time-consuming) tasks periodically. Now I've switched the whole to RxJava. RxJava provides Observable.timer which is simpler, less error-prone, hassle-free to use.

public class BetterTimerFragment extends Fragment {
  public static final String TAG = "BetterTimer";
  private TextView timeView;
  private Subscription timerSubscription;

  public View onCreateView(LayoutInflater inflater,
                           @Nullable ViewGroup container,
                           @Nullable Bundle savedInstanceState) {
    return inflater.inflate(R.layout.fragment_timer, container, false);

  public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    timeView = (TextView) view.findViewById(;

  public void onResume() {

    // Right after the app is visible to users, delay 2 seconds
    // then kick off a (heavy) task every 10 seconds.
    timerSubscription = Observable.timer(2, 10, TimeUnit.SECONDS)
        .map(new Func1<Long, String>() {
          public String call(Long unused) {
            // TODO: Probably do time-consuming work here.
            // This runs on a different thread than the main thread.
            return "Time: " + System.currentTimeMillis();
        .subscribe(new Action1<String>() {
          public void call(String timeText) {
            // The result will then be propagated back to the main thread.
        }, new Action1<Throwable>() {
          public void call(Throwable throwable) {
            Log.e(TAG, throwable.getMessage(), throwable);

  public void onPause() {

    // Don't kick off tasks when the app gets invisible.

Reading a json file in Android

Put that file in assets.

For project created in Android Studio project you need to create assets folder under the main folder.

Read that file as:

public String loadJSONFromAsset(Context context) {
        String json = null;
        try {
            InputStream is = context.getAssets().open("file_name.json");

            int size = is.available();

            byte[] buffer = new byte[size];



            json = new String(buffer, "UTF-8");

        } catch (IOException ex) {
            return null;
        return json;


and then you can simply read this string return by this function as

JSONObject obj = new JSONObject(json_return_by_the_function);

For further details regarding JSON see

Hope you will get what you want.


I uninstalled previous version. It worked for me.

How to get the date from the DatePicker widget in Android?

U can also use te Calendar.GregorianCalendar java class

    GregorianCalendar calendarBeg=new GregorianCalendar(datePicker.getYear(),
    Date begin=calendarBeg.getTime();

Vertical line using XML drawable

Seems like there's a bug when using rotate drawable in Android M and above as per the thread here :

As per my opinion, creating a custom view is the best solution for this.

Below link save my time.

concatenate two strings

You need to use the string concatenation operator +

String both = name + "-" + dest;

How to implement HorizontalScrollView like Gallery?

Try this code:


<RelativeLayout xmlns:android=""
tools:context=".MainActivity" >
    android:scrollbars="none" >
        android:orientation="horizontal" >
            android:orientation="vertical" >
                android:layout_height="match_parent" >
                    android:src="@drawable/action_plan" />
                    android:background="@drawable/ln" />
            android:orientation="vertical" >
                android:layout_height="match_parent" >
                    android:src="@drawable/controlled" />
                    android:background="@drawable/ln" />
            android:orientation="vertical" >
                android:orientation="horizontal" >
                    android:src="@drawable/as_needed" />
                    android:background="@drawable/ln" />
            android:orientation="vertical" >
                android:layout_height="match_parent" >
                    android:src="@drawable/rescue" />
                    android:background="@drawable/ln" />
            android:orientation="vertical" >
                android:layout_height="match_parent" >
                    android:src="@drawable/symptoms" />
                    android:background="@drawable/ln" />
            android:orientation="vertical" >
                android:layout_height="match_parent" >
                    android:src="@drawable/triggers" />
                    android:background="@drawable/ln" />
            android:orientation="vertical" >
                android:layout_height="match_parent" >
                    android:src="@drawable/wheeze_rate" />
                    android:background="@drawable/ln" />
            android:orientation="vertical" >
                android:layout_height="match_parent" >
                    android:src="@drawable/peak_flow" />
                    android:background="@drawable/ln" />
    android:background="@drawable/ln" />
    android:descendantFocusability="blocksDescendants" >
        android:src="@drawable/prev_arrow" />
    android:descendantFocusability="blocksDescendants" >
        android:src="@drawable/next_arrow" />


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android=""
android:orientation="vertical" >
    android:src="@drawable/ic_launcher" />

import java.util.ArrayList;

import android.os.Bundle;
import android.os.Handler;
import android.view.Display;
import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.HorizontalScrollView;
import android.widget.LinearLayout;
import android.widget.LinearLayout.LayoutParams;

public class MainActivity extends Activity {

LinearLayout asthmaActionPlan, controlledMedication, asNeededMedication,
        rescueMedication, yourSymtoms, yourTriggers, wheezeRate, peakFlow;
LayoutParams params;
LinearLayout next, prev;
int viewWidth;
GestureDetector gestureDetector = null;
HorizontalScrollView horizontalScrollView;
ArrayList<LinearLayout> layouts;
int parentLeft, parentRight;
int mWidth;
int currPosition, prevPosition;

protected void onCreate(Bundle savedInstanceState) {

    prev = (LinearLayout) findViewById(;
    next = (LinearLayout) findViewById(;
    horizontalScrollView = (HorizontalScrollView) findViewById(;
    gestureDetector = new GestureDetector(new MyGestureDetector());
    asthmaActionPlan = (LinearLayout) findViewById(;
    controlledMedication = (LinearLayout) findViewById(;
    asNeededMedication = (LinearLayout) findViewById(;
    rescueMedication = (LinearLayout) findViewById(;
    yourSymtoms = (LinearLayout) findViewById(;
    yourTriggers = (LinearLayout) findViewById(;
    wheezeRate = (LinearLayout) findViewById(;
    peakFlow = (LinearLayout) findViewById(;

    Display display = getWindowManager().getDefaultDisplay();
    mWidth = display.getWidth(); // deprecated
    viewWidth = mWidth / 3;
    layouts = new ArrayList<LinearLayout>();
    params = new LayoutParams(viewWidth, LayoutParams.WRAP_CONTENT);



    next.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            new Handler().postDelayed(new Runnable() {
                public void run() {
                            (int) horizontalScrollView.getScrollX()
                                    + viewWidth,
                            (int) horizontalScrollView.getScrollY());
            }, 100L);

    prev.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            new Handler().postDelayed(new Runnable() {
                public void run() {
                            (int) horizontalScrollView.getScrollX()
                                    - viewWidth,
                            (int) horizontalScrollView.getScrollY());
            }, 100L);

    horizontalScrollView.setOnTouchListener(new OnTouchListener() {
        public boolean onTouch(View v, MotionEvent event) {
            if (gestureDetector.onTouchEvent(event)) {
                return true;
            return false;

class MyGestureDetector extends SimpleOnGestureListener {
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
            float velocityY) {
        if (e1.getX() < e2.getX()) {
            currPosition = getVisibleViews("left");
        } else {
            currPosition = getVisibleViews("right");

                .getLeft(), 0);
        return true;

public int getVisibleViews(String direction) {
    Rect hitRect = new Rect();
    int position = 0;
    int rightCounter = 0;
    for (int i = 0; i < layouts.size(); i++) {
        if (layouts.get(i).getLocalVisibleRect(hitRect)) {
            if (direction.equals("left")) {
                position = i;
            } else if (direction.equals("right")) {
                position = i;
                if (rightCounter == 2)
    return position;

Let me know if any issue enjoy...

java.lang.RuntimeException: Unable to start activity ComponentInfo

After trying few answers they are either not related to my project or , I have tried cleaning and rebuilding ( But it didn't work for me directly. I have compared it with older version of code, in which i observed some library files(jars and aars in External Libraries directory) are missing. Tried Invalidate Cache and Restart worked, which created all the libraries and working fine.

How to connect Android app to MySQL database?

The one way is by using webservice, simply write a webservice method in PHP or any other language . And From your android app by using http client request and response , you can hit the web service method which will return whatever you want.

For PHP You can create a webservice like this. Assuming below we have a php file in the server. And the route of the file is

       case 'userlogin':
           //perform your userlogin task here

Now you can use Volley or Retrofit to send a network request to the above PHP Script and then, actually the php script will handle the database operation.

In this case the PHP script is called a RESTful API.

You can learn all the operation at MySQL from this tutorial. Android MySQL Tutorial to Perform CRUD.

Find location of a removable SD card

I came up with the following solution based on some answers found here.


public class ExternalStorage {

    public static final String SD_CARD = "sdCard";
    public static final String EXTERNAL_SD_CARD = "externalSdCard";

     * @return True if the external storage is available. False otherwise.
    public static boolean isAvailable() {
        String state = Environment.getExternalStorageState();
        if (Environment.MEDIA_MOUNTED.equals(state) || Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
            return true;
        return false;

    public static String getSdCardPath() {
        return Environment.getExternalStorageDirectory().getPath() + "/";

     * @return True if the external storage is writable. False otherwise.
    public static boolean isWritable() {
        String state = Environment.getExternalStorageState();
        if (Environment.MEDIA_MOUNTED.equals(state)) {
            return true;
        return false;


     * @return A map of all storage locations available
    public static Map<String, File> getAllStorageLocations() {
        Map<String, File> map = new HashMap<String, File>(10);

        List<String> mMounts = new ArrayList<String>(10);
        List<String> mVold = new ArrayList<String>(10);

        try {
            File mountFile = new File("/proc/mounts");
                Scanner scanner = new Scanner(mountFile);
                while (scanner.hasNext()) {
                    String line = scanner.nextLine();
                    if (line.startsWith("/dev/block/vold/")) {
                        String[] lineElements = line.split(" ");
                        String element = lineElements[1];

                        // don't add the default mount path
                        // it's already in the list.
                        if (!element.equals("/mnt/sdcard"))
        } catch (Exception e) {

        try {
            File voldFile = new File("/system/etc/vold.fstab");
                Scanner scanner = new Scanner(voldFile);
                while (scanner.hasNext()) {
                    String line = scanner.nextLine();
                    if (line.startsWith("dev_mount")) {
                        String[] lineElements = line.split(" ");
                        String element = lineElements[2];

                        if (element.contains(":"))
                            element = element.substring(0, element.indexOf(":"));
                        if (!element.equals("/mnt/sdcard"))
        } catch (Exception e) {

        for (int i = 0; i < mMounts.size(); i++) {
            String mount = mMounts.get(i);
            if (!mVold.contains(mount))

        List<String> mountHash = new ArrayList<String>(10);

        for(String mount : mMounts){
            File root = new File(mount);
            if (root.exists() && root.isDirectory() && root.canWrite()) {
                File[] list = root.listFiles();
                String hash = "[";
                    for(File f : list){
                        hash += f.getName().hashCode()+":"+f.length()+", ";
                hash += "]";
                    String key = SD_CARD + "_" + map.size();
                    if (map.size() == 0) {
                        key = SD_CARD;
                    } else if (map.size() == 1) {
                        key = EXTERNAL_SD_CARD;
                    map.put(key, root);


                 map.put(SD_CARD, Environment.getExternalStorageDirectory());
        return map;


Map<String, File> externalLocations = ExternalStorage.getAllStorageLocations();
File sdCard = externalLocations.get(ExternalStorage.SD_CARD);
File externalSdCard = externalLocations.get(ExternalStorage.EXTERNAL_SD_CARD);

android edittext onchange listener

TextWatcher didn't work for me as it kept firing for every EditText and messing up each others values.

Here is my solution:

public class ConsultantTSView extends Activity {

    //Submit is called when I push submit button.
    //I wanted to retrieve all EditText(tsHours) values in my HoursList

    public void submit(View view){

        ListView TSDateListView = (ListView) findViewById(;
        String value = ((EditText) TSDateListView.getChildAt(0).findViewById(;

Hence by using the getChildAt(xx) method you can retrieve any item in the ListView and get the individual item using findViewById. And it will then give the most recent value.

Android Percentage Layout Height

android:layout_weight=".YOURVALUE" is best way to implement in percentage

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android=""
    android:orientation="vertical" >

        android:text="@string/logText" >


Cannot run emulator in Android Studio

Hey there just ran into the same issue you did, the 3rd link down in google brought me to this bit of code that throws the error,

if (kernelFile == NULL) {
        kernelFile = avdInfo_getKernelPath(avd);
        if (kernelFile == NULL) {
            derror( "This AVD's configuration is missing a kernel file!!" );
            const char* sdkRootDir = getenv("ANDROID_SDK_ROOT");
            if (sdkRootDir) {
                derror( "ANDROID_SDK_ROOT is defined (%s) but cannot find kernel file in "
                        "%s" PATH_SEP "system-images" PATH_SEP
                        " sub directories", sdkRootDir, sdkRootDir);
            } else {
                derror( "ANDROID_SDK_ROOT is undefined");

to which the person wrote:

"/* If the kernel image name ends in "-armv7", then change the cpu * type automatically. This is a poor man's approach to configuration * management, but should allow us to get past building ARMv7 * system images with dex preopt pass"

So I went back in and downloaded the x86 intel atom version for my desired API level and was able to get the emulator up without the error. Hope it helps you too.....

how do you pass images (bitmaps) between android activities using bundles?

Write this code from where you want to Intent into next activity.

    Drawable drawable = ((ImageView)view).getDrawable(); 
    Bitmap bitmap = imageView.getDrawingCache();
    Intent intent = new Intent(getBaseContext(), NextActivity.class);
    intent.putExtra("Image", imageBitmap);

In onCreate Function of NextActivity.class

Bitmap hotel_image;
Intent intent = getIntent();
hotel_image= intent.getParcelableExtra("Image");

Download a file with Android, and showing the progress in a ProgressDialog

There are many ways to download files. Following I will post most common ways; it is up to you to decide which method is better for your app.

1. Use AsyncTask and show the download progress in a dialog

This method will allow you to execute some background processes and update the UI at the same time (in this case, we'll update a progress bar).


import android.os.PowerManager;

This is an example code:

// declare the dialog as a member field of your activity
ProgressDialog mProgressDialog;

// instantiate it within the onCreate method
mProgressDialog = new ProgressDialog(YourActivity.this);
mProgressDialog.setMessage("A message");

// execute this when the downloader must be fired
final DownloadTask downloadTask = new DownloadTask(YourActivity.this);
downloadTask.execute("the url to the file you want to download");

mProgressDialog.setOnCancelListener(new DialogInterface.OnCancelListener() {

    public void onCancel(DialogInterface dialog) {
        downloadTask.cancel(true); //cancel the task

The AsyncTask will look like this:

// usually, subclasses of AsyncTask are declared inside the activity class.
// that way, you can easily modify the UI thread from here
private class DownloadTask extends AsyncTask<String, Integer, String> {

    private Context context;
    private PowerManager.WakeLock mWakeLock;

    public DownloadTask(Context context) {
        this.context = context;

    protected String doInBackground(String... sUrl) {
        InputStream input = null;
        OutputStream output = null;
        HttpURLConnection connection = null;
        try {
            URL url = new URL(sUrl[0]);
            connection = (HttpURLConnection) url.openConnection();

            // expect HTTP 200 OK, so we don't mistakenly save error report
            // instead of the file
            if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
                return "Server returned HTTP " + connection.getResponseCode()
                        + " " + connection.getResponseMessage();

            // this will be useful to display download percentage
            // might be -1: server did not report the length
            int fileLength = connection.getContentLength();

            // download the file
            input = connection.getInputStream();
            output = new FileOutputStream("/sdcard/file_name.extension");

            byte data[] = new byte[4096];
            long total = 0;
            int count;
            while ((count = != -1) {
                // allow canceling with back button
                if (isCancelled()) {
                    return null;
                total += count;
                // publishing the progress....
                if (fileLength > 0) // only if total length is known
                    publishProgress((int) (total * 100 / fileLength));
                output.write(data, 0, count);
        } catch (Exception e) {
            return e.toString();
        } finally {
            try {
                if (output != null)
                if (input != null)
            } catch (IOException ignored) {

            if (connection != null)
        return null;

The method above (doInBackground) runs always on a background thread. You shouldn't do any UI tasks there. On the other hand, the onProgressUpdate and onPreExecute run on the UI thread, so there you can change the progress bar:

    protected void onPreExecute() {
        // take CPU lock to prevent CPU from going off if the user 
        // presses the power button during download
        PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
        mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,

    protected void onProgressUpdate(Integer... progress) {
        // if we get here, length is known, now set indeterminate to false

    protected void onPostExecute(String result) {
        if (result != null)
            Toast.makeText(context,"Download error: "+result, Toast.LENGTH_LONG).show();
            Toast.makeText(context,"File downloaded", Toast.LENGTH_SHORT).show();

For this to run, you need the WAKE_LOCK permission.

<uses-permission android:name="android.permission.WAKE_LOCK" />

2. Download from Service

The big question here is: how do I update my activity from a service?. In the next example we are going to use two classes you may not be aware of: ResultReceiver and IntentService. ResultReceiver is the one that will allow us to update our thread from a service; IntentService is a subclass of Service which spawns a thread to do background work from there (you should know that a Service runs actually in the same thread of your app; when you extends Service, you must manually spawn new threads to run CPU blocking operations).

Download service can look like this:

public class DownloadService extends IntentService {
    public static final int UPDATE_PROGRESS = 8344;

    public DownloadService() {
    protected void onHandleIntent(Intent intent) {

        String urlToDownload = intent.getStringExtra("url");
        ResultReceiver receiver = (ResultReceiver) intent.getParcelableExtra("receiver");
        try {

            //create url and connect
            URL url = new URL(urlToDownload);
            URLConnection connection = url.openConnection();

            // this will be useful so that you can show a typical 0-100% progress bar
            int fileLength = connection.getContentLength();

            // download the file
            InputStream input = new BufferedInputStream(connection.getInputStream());

            String path = "/sdcard/BarcodeScanner-debug.apk" ;
            OutputStream output = new FileOutputStream(path);

            byte data[] = new byte[1024];
            long total = 0;
            int count;
            while ((count = != -1) {
                total += count;

                // publishing the progress....
                Bundle resultData = new Bundle();
                resultData.putInt("progress" ,(int) (total * 100 / fileLength));
                receiver.send(UPDATE_PROGRESS, resultData);
                output.write(data, 0, count);

            // close streams 

        } catch (IOException e) {

        Bundle resultData = new Bundle();
        resultData.putInt("progress" ,100);

        receiver.send(UPDATE_PROGRESS, resultData);

Add the service to your manifest:

<service android:name=".DownloadService"/>

And the activity will look like this:

// initialize the progress dialog like in the first example

// this is how you fire the downloader;
Intent intent = new Intent(this, DownloadService.class);
intent.putExtra("url", "url of the file to download");
intent.putExtra("receiver", new DownloadReceiver(new Handler()));

Here is were ResultReceiver comes to play:

private class DownloadReceiver extends ResultReceiver{

    public DownloadReceiver(Handler handler) {

    protected void onReceiveResult(int resultCode, Bundle resultData) {

        super.onReceiveResult(resultCode, resultData);

        if (resultCode == DownloadService.UPDATE_PROGRESS) {

            int progress = resultData.getInt("progress"); //get the progress

            if (progress == 100) {

2.1 Use Groundy library

Groundy is a library that basically helps you run pieces of code in a background service, and it is based on the ResultReceiver concept shown above. This library is deprecated at the moment. This is how the whole code would look like:

The activity where you are showing the dialog...

public class MainActivity extends Activity {

    private ProgressDialog mProgressDialog;

    public void onCreate(Bundle savedInstanceState) {

        findViewById( View.OnClickListener() {
            public void onClick(View view) {
                String url = ((EditText) findViewById(;
                Bundle extras = new Bundler().add(DownloadTask.PARAM_URL, url).build();
                Groundy.create(DownloadExample.this, DownloadTask.class)

                mProgressDialog = new ProgressDialog(MainActivity.this);

    private ResultReceiver mReceiver = new ResultReceiver(new Handler()) {
        protected void onReceiveResult(int resultCode, Bundle resultData) {
            super.onReceiveResult(resultCode, resultData);
            switch (resultCode) {
                case Groundy.STATUS_PROGRESS:
                case Groundy.STATUS_FINISHED:
                    Toast.makeText(DownloadExample.this, R.string.file_downloaded, Toast.LENGTH_LONG);
                case Groundy.STATUS_ERROR:
                    Toast.makeText(DownloadExample.this, resultData.getString(Groundy.KEY_ERROR), Toast.LENGTH_LONG).show();

A GroundyTask implementation used by Groundy to download the file and show the progress:

public class DownloadTask extends GroundyTask {    
    public static final String PARAM_URL = "com.groundy.sample.param.url";

    protected boolean doInBackground() {
        try {
            String url = getParameters().getString(PARAM_URL);
            File dest = new File(getContext().getFilesDir(), new File(url).getName());
            DownloadUtils.downloadFile(getContext(), url, dest, DownloadUtils.getDownloadListenerForTask(this));
            return true;
        } catch (Exception pokemon) {
            return false;

And just add this to the manifest:

<service android:name="com.codeslap.groundy.GroundyService"/>

It couldn't be easier I think. Just grab the latest jar from Github and you are ready to go. Keep in mind that Groundy's main purpose is to make calls to external REST apis in a background service and post results to the UI with easily. If you are doing something like that in your app, it could be really useful.

2.2 Use

3. Use DownloadManager class (GingerBread and newer only)

GingerBread brought a new feature, DownloadManager, which allows you to download files easily and delegate the hard work of handling threads, streams, etc. to the system.

First, let's see a utility method:

 * @param context used to check the device version and DownloadManager information
 * @return true if the download manager is available
public static boolean isDownloadManagerAvailable(Context context) {

        return true;
    return false;

Method's name explains it all. Once you are sure DownloadManager is available, you can do something like this:

String url = "url you want to download";
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
request.setDescription("Some descrition");
request.setTitle("Some title");
// in order for this if to run, you must use the android 3.2 to compile your app
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "name-of-the-file.ext");

// get download service and enqueue file
DownloadManager manager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);

Download progress will be showing in the notification bar.

Final thoughts

First and second methods are just the tip of the iceberg. There are lots of things you have to keep in mind if you want your app to be robust. Here is a brief list:

  • You must check whether user has an internet connection available
  • Make sure you have the right permissions (INTERNET and WRITE_EXTERNAL_STORAGE); also ACCESS_NETWORK_STATE if you want to check internet availability.
  • Make sure the directory were you are going to download files exist and has write permissions.
  • If download is too big you may want to implement a way to resume the download if previous attempts failed.
  • Users will be grateful if you allow them to interrupt the download.

Unless you need detailed control of the download process, then consider using DownloadManager (3) because it already handles most of the items listed above.

But also consider that your needs may change. For example, DownloadManager does no response caching. It will blindly download the same big file multiple times. There's no easy way to fix it after the fact. Where if you start with a basic HttpURLConnection (1, 2), then all you need is to add an HttpResponseCache. So the initial effort of learning the basic, standard tools can be a good investment.

This class was deprecated in API level 26. ProgressDialog is a modal dialog, which prevents the user from interacting with the app. Instead of using this class, you should use a progress indicator like ProgressBar, which can be embedded in your app's UI. Alternatively, you can use a notification to inform the user of the task's progress. For more details Link

How to use "Share image using" sharing Intent to share images in android?

First add permission

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

using Bitmap from resources

Bitmap b =BitmapFactory.decodeResource(getResources(),R.drawable.userimage);
Intent share = new Intent(Intent.ACTION_SEND);
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
b.compress(Bitmap.CompressFormat.JPEG, 100, bytes);
String path = MediaStore.Images.Media.insertImage(getContentResolver(), b, "Title", null);
Uri imageUri =  Uri.parse(path);
share.putExtra(Intent.EXTRA_STREAM, imageUri);
startActivity(Intent.createChooser(share, "Select"));

Tested via bluetooth and other messengers

How to create a link for all mobile devices that opens google maps with a route starting at the current location, destinating a given place?

Interestingly, links will open directly in Apple Maps on an iOS device, or redirect to Google Maps otherwise (which is then intercepted on an Android device), so you can craft a careful URL that will do the right thing in both cases using an "Apple Maps" URL like:,+Mountain+View+CA

Alternatively, you can use a Google Maps url directly (without the /maps URL component) to open directly in Google Maps on an Android device, or open in Google Maps' Mobile Web on an iOS device:,+Cupertino+CA

how to get current location in google map android

  1. Select google map activity

    enter image description here

  2. you need a Google Maps API key.

    To get one, follow this link, follow the directions and press "Create" at the end:

  3. Paste this Code in

import android.Manifest;
import android.location.Location;
import android.os.Build;

import android.os.Bundle;

import android.widget.Toast;

import androidx.core.content.ContextCompat;


  public class MapsActivity extends FragmentActivity implement
    @private GoogleMap mMap;
        GoogleApiClient mGoogleApiClient;
        Location mLastLocation;
        Marker mCurrLocationMarker;
        LocationRequest mLocationRequest;
        protected void onCreate(Bundle savedInstanceState) {

            if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            // Obtain the SupportMapFragment and get notified when the map is ready to be used.
            SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()

        public void onMapReady(GoogleMap googleMap) {
            mMap = googleMap;

            //Initialize Google Play Services
            if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                if (ContextCompat.checkSelfPermission(this,
                        Manifest.permission.ACCESS_FINE_LOCATION) ==
                    PackageManager.PERMISSION_GRANTED) {
            } else {

        protected synchronized void buildGoogleApiClient() {
            mGoogleApiClient = new GoogleApiClient.Builder(this)

        public void onConnected(Bundle bundle) {

            mLocationRequest = new LocationRequest();
            if (ContextCompat.checkSelfPermission(this,
                    Manifest.permission.ACCESS_FINE_LOCATION) ==
                PackageManager.PERMISSION_GRANTED) {
                LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);


        public void onConnectionSuspended(int i) {


        public void onLocationChanged(Location location) {

            mLastLocation = location;
            if (mCurrLocationMarker != null) {

            //Place current location marker
            LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
            MarkerOptions markerOptions = new MarkerOptions();
            markerOptions.title("Current Position");
            mCurrLocationMarker = mMap.addMarker(markerOptions);

            //move map camera

            //stop location updates
            if (mGoogleApiClient != null) {
                LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);


        public void onConnectionFailed(ConnectionResult connectionResult) {


        public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
        public boolean checkLocationPermission() {
            if (ContextCompat.checkSelfPermission(this,
                    Manifest.permission.ACCESS_FINE_LOCATION) !=
                PackageManager.PERMISSION_GRANTED) {

                // Asking user if explanation is needed
                if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                        Manifest.permission.ACCESS_FINE_LOCATION)) {

                    // Show an explanation to the user *asynchronously* -- don't block
                    // this thread waiting for the user's response! After the user
                    // sees the explanation, try again to request the permission.

                    //Prompt the user once explanation has been shown
                        new String[] {

                } else {
                    // No explanation needed, we can request the permission.
                        new String[] {
                return false;
            } else {
                return true;

        public void onRequestPermissionsResult(int requestCode,
            String permissions[], int[] grantResults) {
            switch (requestCode) {
                        // If request is cancelled, the result arrays are empty.
                        if (grantResults.length > 0 &&
                            grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                            // permission was granted. Do the
                            // contacts-related task you need to do.
                            if (ContextCompat.checkSelfPermission(this,
                                    Manifest.permission.ACCESS_FINE_LOCATION) ==
                                PackageManager.PERMISSION_GRANTED) {

                                if (mGoogleApiClient == null) {

                        } else {

                            // Permission denied, Disable the functionality that depends on this permission.
                            Toast.makeText(this, "permission denied", Toast.LENGTH_LONG).show();

  1. Make sure these permission are written in Manifest file

    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    enter image description here

  2. Add following dependencies

    implementation ''

    implementation ''

    enter image description here

How to save an activity state using save instance state?

Now Android provides ViewModels for saving state, you should try to use that instead of saveInstanceState.

Declaring a custom android UI element using XML

Thanks a lot for the first answer.

As for me, I had just one problem with it. When inflating my view, i had a bug : java.lang.NoSuchMethodException : MyView(Context, Attributes)

I resolved it by creating a new constructor :

public MyView(Context context, AttributeSet attrs) {
     super(context, attrs);
     // some code

Hope this will help !

How do I start an activity from within a Fragment?

I done it, below code is working for me....

    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.hello_world, container, false);

        Button newPage = (Button)v.findViewById(;
        newPage.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {
                Intent intent = new Intent(getActivity(), HomeActivity.class);
        return v;

and Please make sure that your destination activity should be register in Manifest.xml file,

but in my case all tabs are not shown in HomeActivity, is any solution for that ?

Send push to Android by C# using FCM (Firebase Cloud Messaging)

firebase cloud messaging with c#: working all .net platform (, .netmvc, .netcore)

        WebRequest tRequest = WebRequest.Create("");
        tRequest.Method = "post";
        //serverKey - Key from Firebase cloud messaging server  
        tRequest.Headers.Add(string.Format("Authorization: key={0}", "AIXXXXXX...."));
        //Sender Id - From firebase project setting  
        tRequest.Headers.Add(string.Format("Sender: id={0}", "XXXXX.."));
        tRequest.ContentType = "application/json";
        var payload = new
            to = "e8EHtMwqsZY:APA91bFUktufXdsDLdXXXXXX..........XXXXXXXXXXXXXX",
            priority = "high",
            content_available = true,
            notification = new
                body = "Test",
                title = "Test",
                badge = 1
            data = new 
                key1 = "value1",
                key2 = "value2"


        string postbody = JsonConvert.SerializeObject(payload).ToString();
        Byte[] byteArray = Encoding.UTF8.GetBytes(postbody);
        tRequest.ContentLength = byteArray.Length;
        using (Stream dataStream = tRequest.GetRequestStream())
            dataStream.Write(byteArray, 0, byteArray.Length);
            using (WebResponse tResponse = tRequest.GetResponse())
                using (Stream dataStreamResponse = tResponse.GetResponseStream())
                    if (dataStreamResponse != null) using (StreamReader tReader = new StreamReader(dataStreamResponse))
                            String sResponseFromServer = tReader.ReadToEnd();
                            //result.Response = sResponseFromServer;

How to emulate GPS location in the Android Emulator?

In Linux where communication ports are blocked. navigate the terminal to platform-tools folder inside android sdk and fire this command:

./adb -s #{device_name} emu geo fix #{longitude} #{latitude}

Android: why is there no maxHeight for a View?

As we know devices running android can have different screen sizes. As we further know views should adjust dynamically and become the space which is appropriate.

If you set a max height you maybe force the view not to get enough space or take to less space. I know that sometimes it seems to be practically to set a max height. But if the resolution will ever change dramatically, and it will!, then the view, which has a max height, will look not appropriate.

i think there is no proper way to exactly do the layout you want. i would recommend you to think over your layout using layout managers and relative mechanisms. i don't know what you're trying to achieve but it sounds a little strange for me that a list should only show three items and then the user has to scroll.

btw. minHeight is not guaranteed (and maybe shouldn't exist either). it can have some benefit to force items to be visible while other relative items get smaller.

Couldn't load memtrack module Logcat Error

This error, as you can read on the question linked in comments above, results to be:

"[...] a problem with loading {some} hardware module. This could be something to do with GPU support, sdcard handling, basically anything."

The step 1 below should resolve this problem. Also as I can see, you have some strange package names inside your manifest:

  • package="com.example.hive" in <manifest> tag,
  • android:name="" for <application>
  • and android:name="com.sit.gems.activity" in <activity>

As you know, these things do not prevent your app to be displayed. But I think:

the Couldn't load memtrack module error could occur because of emulators configurations problems and, because your project contains many organization problems, it might help to give a fresh redesign.

For better using and with few things, this can be resolved by following these tips:

1. Try an other emulator...

And even a real device! The memtrack module error seems related to your emulator. So change it into Run configuration, don't forget to change the API too.

2. OpenGL error logs

For OpenGl errors, as called unimplemented OpenGL ES API, it's not an error but a statement! You should enable it in your manifest (you can read this answer if you're using GLSurfaceView inside, it might help you):

<uses-feature android:glEsVersion="0x00020000"></uses-feature>  
// or
<uses-feature android:glEsVersion="0x00010001" android:required="true" />

3. Use the same package

Don't declare different package names to all the tags in Manifest. You should have the same for Manifest, Activities, etc. Something like this looks right:

<!-- set the general package -->
<manifest xmlns:android=""
    android:versionName="1.0" >

    <!-- don't set a package name in <application> -->
    <application ... >

        <!-- then, declare the activities -->
            android:name="com.sit.gems.activity.SplashActivity" ... >
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
        <!-- same package here -->
            android:name="com.sit.gems.activity.HomeActivity" ... >

4. Don't get lost with layouts:

You should set another layout for because you're not using the TabHost for the splash screen and this is not a safe resource way. Declare a specific layout with something different, like the app name and the logo:

// inside SplashScreen class

// layout splash_screen.xml
<TextView xmlns:android=""
     android:text="@string/appname" />  

Avoid using a layout in activities which don't use it.

5. Splash Screen?

Finally, I don't understand clearly the purpose of your SplashScreenActivity. It sets a content view and directly finish. This is useless.

As its name is Splash Screen, I assume that you want to display a screen before launching your HomeActivity. Therefore, you should do this and don't use the TabHost layout ;):

// FragmentActivity is also useless here! You don't use a Fragment into it, so, use traditional Activity
public class SplashActivity extends Activity {
    protected void onCreate(Bundle savedInstanceState) {
        // set your splash_screen layout

        // create a new Thread
        new Thread(new Runnable() {
            public void run() {
                try {
                    // sleep during 800ms
                } catch (InterruptedException e) {
                // start HomeActivity
                startActivity(new Intent(SplashActivity.this, HomeActivity.class));

I hope this kind of tips help you to achieve what you want.
If it's not the case, let me know how can I help you.

getting exception "IllegalStateException: Can not perform this action after onSaveInstanceState"

My solution for that problem was

In fragment add methods:

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    guideMapFragment = (SupportMapFragment)a.getSupportFragmentManager().findFragmentById(;
    guideMap = guideMapFragment.getMap();

public void onDestroyView() {
    SherlockFragmentActivity a = getSherlockActivity();
    if (a != null && guideMapFragment != null) {
        try {
            Log.i(LOGTAG, "Removing map fragment");
            guideMapFragment = null;
        } catch(IllegalStateException e) {
            Log.i(LOGTAG, "IllegalStateException on exit");

May be bad, but couldn't find anything better.

How to set up gradle and android studio to do release build?

To activate the installRelease task, you simply need a signingConfig. That is all.


Finally, the plugin creates install/uninstall tasks for all build types (debug, release, test), as long as they can be installed (which requires signing).

Here is what you want:

Install tasks
installDebug - Installs the Debug build
installDebugTest - Installs the Test build for the Debug build
installRelease - Installs the Release build
uninstallAll - Uninstall all applications.
uninstallDebug - Uninstalls the Debug build
uninstallDebugTest - Uninstalls the Test build for the Debug build
uninstallRelease - Uninstalls the Release build   <--- release

Here is how to obtain the installRelease task:

Example build.gradle:

buildscript {
    repositories {

    dependencies {
        classpath ''

apply plugin: ''

android {
  compileSdkVersion 22
  buildToolsVersion '22.0.1'

  defaultConfig {
    applicationId 'demo'
    minSdkVersion 15
    targetSdkVersion 22
    versionCode 1
    versionName '1.0'

  signingConfigs {
      release {
          storeFile <file>
          storePassword <password>
          keyAlias <alias>
          keyPassword <password>

  buildTypes {
    release {
        signingConfig signingConfigs.release

Set inputType for an EditText Programmatically?


//you can change TYPE_... according to your requirement.

How to detect when an Android app goes to the background and come back to the foreground

You can achieve this easily with the help of ActivityLifecycleCallbacks and ComponentCallbacks2 something like below.

Create a class AppLifeCycleHandler implementing above said interfaces.


import android.content.ComponentCallbacks2;
import android.content.res.Configuration;
import android.os.Bundle;

 * Created by Naveen on 17/04/18
public class AppLifeCycleHandler
    implements Application.ActivityLifecycleCallbacks, ComponentCallbacks2 {

  AppLifeCycleCallback appLifeCycleCallback;

  boolean appInForeground;

  public AppLifeCycleHandler(AppLifeCycleCallback appLifeCycleCallback) {
    this.appLifeCycleCallback = appLifeCycleCallback;

  public void onActivityResumed(Activity activity) {
    if (!appInForeground) {
      appInForeground = true;

  public void onTrimMemory(int i) {
    if (i == ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) {
      appInForeground = false;

  public void onActivityCreated(Activity activity, Bundle bundle) {


  public void onActivityStarted(Activity activity) {


  public void onActivityPaused(Activity activity) {


  public void onActivityStopped(Activity activity) {


  public void onActivitySaveInstanceState(Activity activity, Bundle bundle) {


  public void onActivityDestroyed(Activity activity) {


  public void onConfigurationChanged(Configuration configuration) {


  public void onLowMemory() {


  interface AppLifeCycleCallback {

    void onAppBackground();

    void onAppForeground();

In your class which extends Application implement AppLifeCycleCallback to get the callbacks when app switches between foreground and background. Something like below.

public class BaseApplication extends Application implements AppLifeCycleHandler.AppLifeCycleCallback{

    public void onCreate() {
        AppLifeCycleHandler appLifeCycleHandler = new AppLifeCycleHandler(this);

    public void onAppBackground() {
        Log.d("LifecycleEvent", "onAppBackground");

    public void onAppForeground() {
        Log.d("LifecycleEvent", "onAppForeground");

Hope this helps.

EDIT As an alternative you can now use Life cycle aware architecture component.

Charts for Android

SciChart for Android is a relative newcomer, but brings extremely fast high performance real-time charting to the Android platform.

SciChart is a commercial control but available under royalty free distribution / per developer licensing. There is also free licensing available for educational use with some conditions.

Some useful links can be found below:

enter image description here

Disclosure: I am the tech lead on the SciChart project!

Android WebView style background-color:transparent ignored on android 2.2

I was trying to put a transparent HTML overlay over my GL view but it has always black flickering which covers my GL view. After several days trying to get rid of this flickering I found this workaround which is acceptable for me (but a shame for android).

The problem is that I need hardware acceleration for my nice CSS animations and so webView.setLayerType(View.LAYER_TYPE_SOFTWARE, null); is not an option for me.

The trick was to put a second (empty) WebView between my GL view and the HTML overlay. This dummyWebView I told to render in SW mode, and now my HTML overlays renders smooth in HW and no more black flickering.

I don't know if this works on other devices than My Acer Iconia A700, but I hope I could help someone with this.

public class MyActivity extends Activity {

    protected void onCreate(Bundle icicle) {

        RelativeLayout layout = new RelativeLayout(getApplication());

        MyGlView glView = new MyGlView(this);

        RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT, RelativeLayout.LayoutParams.MATCH_PARENT);

        dummyWebView = new WebView(this);
        dummyWebView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        dummyWebView.loadData("", "text/plain", "utf8");

        webView = new WebView(this);


App crashing when trying to use RecyclerView on android 5.0

I had this problem when using Butterknife , I was using fragment

For Fragment, it should be ButterKnife.bind(this,view);

For Activity ButterKnife.bind(this);

No tests found for given includes Error, when running Parameterized Unit test in Android Studio

For me, the cause of the error message

No tests found for given includes

was having inadvertently added a .java test file under my src/test/kotlin test directory. Upon moving the file to the correct directory, src/test/java, the test executed as expected again.

Singletons vs. Application Context in Android?

I very much disagree with Dianne Hackborn's response. We are bit by bit removing all singletons from our project in favor of lightweight, task scoped objects which can easiliy be re-created when you actually need them.

Singletons are a nightmare for testing and, if lazily initialized, will introduce "state indeterminism" with subtle side effects (which may suddenly surface when moving calls to getInstance() from one scope to another). Visibility has been mentioned as another problem, and since singletons imply "global" (= random) access to shared state, subtle bugs may arise when not properly synchronized in concurrent applications.

I consider it an anti-pattern, it's a bad object-oriented style that essentially amounts to maintaining global state.

To come back to your question:

Although the app context can be considered a singleton itself, it is framework-managed and has a well defined life-cycle, scope, and access path. Hence I believe that if you do need to manage app-global state, it should go here, nowhere else. For anything else, rethink if you really need a singleton object, or if it would also be possible to rewrite your singleton class to instead instantiate small, short-lived objects that perform the task at hand.

Display Animated GIF


Image Loader Library for Android, recommended by Google.

  • Glide is quite similar to Picasso but this is much faster than Picasso.
  • Glide consumes less memory than Picasso.

What that Glide has but Picasso doesn't

An ability to load GIF Animation to a simple ImageView might be the most interesting feature of Glide. And yes, you can't do that with Picasso. enter image description here Some important links-


Load image from url

URL url = new URL("");
Bitmap bmp = BitmapFactory.decodeStream(url.openConnection().getInputStream());

Android:java.lang.OutOfMemoryError: Failed to allocate a 23970828 byte allocation with 2097152 free bytes and 2MB until OOM

OutOfMemoryError is the most common problem that occurs in android while especially dealing with bitmaps. This error is thrown by the Java Virtual Machine (JVM) when an object cannot be allocated due to lack of memory space and also, the garbage collector cannot free some space.

As mentioned by Aleksey, you can add the below entities in your manifest file android:hardwareAccelerated="false" , android:largeHeap="true" it will work for some environments.


you should definitely read some of Androids Developer concept's, especially here:Displaying Bitmaps Efficiently

Read all 5 topics and rewrite your code again. If it still doesn't work we will be happy to see what you've done wrong with the tutorial material.

Here some of the possible answers for these type of errors in SOF

Android: BitmapFactory.decodeStream() out of memory with a 400KB file with 2MB free heap

How to solve java.lang.OutOfMemoryError trouble in Android

Android : java.lang.OutOfMemoryError


Solution for OutOfMemoryError: bitmap size exceeds VM budget

Edit: From the comments of @cjnash

For anyone that still had crashes after they added this line, try sticking your image into your res/drawable-xhdpi/ folder instead of your res/drawable/ and it might resolve your issue.

What are the default color values for the Holo theme on Android 4.0?

If you want the default colors of Android ICS, you just have to go to your Android SDK and look for this path: platforms\android-15\data\res\values\colors.xml.

Here you go:

<!-- For holo theme -->
    <drawable name="screen_background_holo_light">#fff3f3f3</drawable>
    <drawable name="screen_background_holo_dark">#ff000000</drawable>
    <color name="background_holo_dark">#ff000000</color>
    <color name="background_holo_light">#fff3f3f3</color>
    <color name="bright_foreground_holo_dark">@android:color/background_holo_light</color>
    <color name="bright_foreground_holo_light">@android:color/background_holo_dark</color>
    <color name="bright_foreground_disabled_holo_dark">#ff4c4c4c</color>
    <color name="bright_foreground_disabled_holo_light">#ffb2b2b2</color>
    <color name="bright_foreground_inverse_holo_dark">@android:color/bright_foreground_holo_light</color>
    <color name="bright_foreground_inverse_holo_light">@android:color/bright_foreground_holo_dark</color>
    <color name="dim_foreground_holo_dark">#bebebe</color>
    <color name="dim_foreground_disabled_holo_dark">#80bebebe</color>
    <color name="dim_foreground_inverse_holo_dark">#323232</color>
    <color name="dim_foreground_inverse_disabled_holo_dark">#80323232</color>
    <color name="hint_foreground_holo_dark">#808080</color>
    <color name="dim_foreground_holo_light">#323232</color>
    <color name="dim_foreground_disabled_holo_light">#80323232</color>
    <color name="dim_foreground_inverse_holo_light">#bebebe</color>
    <color name="dim_foreground_inverse_disabled_holo_light">#80bebebe</color>
    <color name="hint_foreground_holo_light">#808080</color>
    <color name="highlighted_text_holo_dark">#6633b5e5</color>
    <color name="highlighted_text_holo_light">#6633b5e5</color>
    <color name="link_text_holo_dark">#5c5cff</color>
    <color name="link_text_holo_light">#0000ee</color>

This for the Background:

<color name="background_holo_dark">#ff000000</color>
<color name="background_holo_light">#fff3f3f3</color>

You won't get the same colors if you look this up in Photoshop etc. because they are set up with Alpha values.

Update for API Level 19:

    <drawable name="screen_background_light">#ffffffff</drawable>
    <drawable name="screen_background_dark">#ff000000</drawable>
    <drawable name="status_bar_closed_default_background">#ff000000</drawable>
    <drawable name="status_bar_opened_default_background">#ff000000</drawable>
    <drawable name="notification_item_background_color">#ff111111</drawable>
    <drawable name="notification_item_background_color_pressed">#ff454545</drawable>
    <drawable name="search_bar_default_color">#ff000000</drawable>
    <drawable name="safe_mode_background">#60000000</drawable>
    <!-- Background drawable that can be used for a transparent activity to
         be able to display a dark UI: this darkens its background to make
         a dark (default theme) UI more visible. -->
    <drawable name="screen_background_dark_transparent">#80000000</drawable>
    <!-- Background drawable that can be used for a transparent activity to
         be able to display a light UI: this lightens its background to make
         a light UI more visible. -->
    <drawable name="screen_background_light_transparent">#80ffffff</drawable>
    <color name="safe_mode_text">#80ffffff</color>
    <color name="white">#ffffffff</color>
    <color name="black">#ff000000</color>
    <color name="transparent">#00000000</color>
    <color name="background_dark">#ff000000</color>
    <color name="background_light">#ffffffff</color>
    <color name="bright_foreground_dark">@android:color/background_light</color>
    <color name="bright_foreground_light">@android:color/background_dark</color>
    <color name="bright_foreground_dark_disabled">#80ffffff</color>
    <color name="bright_foreground_light_disabled">#80000000</color>
    <color name="bright_foreground_dark_inverse">@android:color/bright_foreground_light</color>
    <color name="bright_foreground_light_inverse">@android:color/bright_foreground_dark</color>
    <color name="dim_foreground_dark">#bebebe</color>
    <color name="dim_foreground_dark_disabled">#80bebebe</color>
    <color name="dim_foreground_dark_inverse">#323232</color>
    <color name="dim_foreground_dark_inverse_disabled">#80323232</color>
    <color name="hint_foreground_dark">#808080</color>
    <color name="dim_foreground_light">#323232</color>
    <color name="dim_foreground_light_disabled">#80323232</color>
    <color name="dim_foreground_light_inverse">#bebebe</color>
    <color name="dim_foreground_light_inverse_disabled">#80bebebe</color>
    <color name="hint_foreground_light">#808080</color>
    <color name="highlighted_text_dark">#9983CC39</color>
    <color name="highlighted_text_light">#9983CC39</color>
    <color name="link_text_dark">#5c5cff</color>
    <color name="link_text_light">#0000ee</color>
    <color name="suggestion_highlight_text">#177bbd</color>

    <drawable name="stat_notify_sync_noanim">@drawable/stat_notify_sync_anim0</drawable>
    <drawable name="stat_sys_download_done">@drawable/stat_sys_download_done_static</drawable>
    <drawable name="stat_sys_upload_done">@drawable/stat_sys_upload_anim0</drawable>
    <drawable name="dialog_frame">@drawable/panel_background</drawable>
    <drawable name="alert_dark_frame">@drawable/popup_full_dark</drawable>
    <drawable name="alert_light_frame">@drawable/popup_full_bright</drawable>
    <drawable name="menu_frame">@drawable/menu_background</drawable>
    <drawable name="menu_full_frame">@drawable/menu_background_fill_parent_width</drawable>
    <drawable name="editbox_dropdown_dark_frame">@drawable/editbox_dropdown_background_dark</drawable>
    <drawable name="editbox_dropdown_light_frame">@drawable/editbox_dropdown_background</drawable>

    <drawable name="dialog_holo_dark_frame">@drawable/dialog_full_holo_dark</drawable>
    <drawable name="dialog_holo_light_frame">@drawable/dialog_full_holo_light</drawable>

    <drawable name="input_method_fullscreen_background">#fff9f9f9</drawable>
    <drawable name="input_method_fullscreen_background_holo">@drawable/screen_background_holo_dark</drawable>
    <color name="input_method_navigation_guard">#ff000000</color>

    <!-- For date picker widget -->
    <drawable name="selected_day_background">#ff0092f4</drawable>

    <!-- For settings framework -->
    <color name="lighter_gray">#ddd</color>
    <color name="darker_gray">#aaa</color>

    <!-- For security permissions -->
    <color name="perms_dangerous_grp_color">#33b5e5</color>
    <color name="perms_dangerous_perm_color">#33b5e5</color>
    <color name="shadow">#cc222222</color>
    <color name="perms_costs_money">#ffffbb33</color>

    <!-- For search-related UIs -->
    <color name="search_url_text_normal">#7fa87f</color>
    <color name="search_url_text_selected">@android:color/black</color>
    <color name="search_url_text_pressed">@android:color/black</color>
    <color name="search_widget_corpus_item_background">@android:color/lighter_gray</color>

    <!-- SlidingTab -->
    <color name="sliding_tab_text_color_active">@android:color/black</color>
    <color name="sliding_tab_text_color_shadow">@android:color/black</color>

    <!-- keyguard tab -->
    <color name="keyguard_text_color_normal">#ffffff</color>
    <color name="keyguard_text_color_unlock">#a7d84c</color>
    <color name="keyguard_text_color_soundoff">#ffffff</color>
    <color name="keyguard_text_color_soundon">#e69310</color>
    <color name="keyguard_text_color_decline">#fe0a5a</color>

    <!-- keyguard clock -->
    <color name="lockscreen_clock_background">#ffffffff</color>
    <color name="lockscreen_clock_foreground">#ffffffff</color>
    <color name="lockscreen_clock_am_pm">#ffffffff</color>
    <color name="lockscreen_owner_info">#ff9a9a9a</color>

    <!-- keyguard overscroll widget pager -->
    <color name="kg_multi_user_text_active">#ffffffff</color>
    <color name="kg_multi_user_text_inactive">#ff808080</color>
    <color name="kg_widget_pager_gradient">#ffffffff</color>

    <!-- FaceLock -->
    <color name="facelock_spotlight_mask">#CC000000</color>

    <!-- For holo theme -->
      <drawable name="screen_background_holo_light">#fff3f3f3</drawable>
      <drawable name="screen_background_holo_dark">#ff000000</drawable>
    <color name="background_holo_dark">#ff000000</color>
    <color name="background_holo_light">#fff3f3f3</color>
    <color name="bright_foreground_holo_dark">@android:color/background_holo_light</color>
    <color name="bright_foreground_holo_light">@android:color/background_holo_dark</color>
    <color name="bright_foreground_disabled_holo_dark">#ff4c4c4c</color>
    <color name="bright_foreground_disabled_holo_light">#ffb2b2b2</color>
    <color name="bright_foreground_inverse_holo_dark">@android:color/bright_foreground_holo_light</color>
    <color name="bright_foreground_inverse_holo_light">@android:color/bright_foreground_holo_dark</color>
    <color name="dim_foreground_holo_dark">#bebebe</color>
    <color name="dim_foreground_disabled_holo_dark">#80bebebe</color>
    <color name="dim_foreground_inverse_holo_dark">#323232</color>
    <color name="dim_foreground_inverse_disabled_holo_dark">#80323232</color>
    <color name="hint_foreground_holo_dark">#808080</color>
    <color name="dim_foreground_holo_light">#323232</color>
    <color name="dim_foreground_disabled_holo_light">#80323232</color>
    <color name="dim_foreground_inverse_holo_light">#bebebe</color>
    <color name="dim_foreground_inverse_disabled_holo_light">#80bebebe</color>
    <color name="hint_foreground_holo_light">#808080</color>
    <color name="highlighted_text_holo_dark">#6633b5e5</color>
    <color name="highlighted_text_holo_light">#6633b5e5</color>
    <color name="link_text_holo_dark">#5c5cff</color>
    <color name="link_text_holo_light">#0000ee</color>

    <!-- Group buttons -->
    <eat-comment />
    <color name="group_button_dialog_pressed_holo_dark">#46c5c1ff</color>
    <color name="group_button_dialog_focused_holo_dark">#2699cc00</color>

    <color name="group_button_dialog_pressed_holo_light">#ffffffff</color>
    <color name="group_button_dialog_focused_holo_light">#4699cc00</color>

    <!-- Highlight colors for the legacy themes -->
    <eat-comment />
    <color name="legacy_pressed_highlight">#fffeaa0c</color>
    <color name="legacy_selected_highlight">#fff17a0a</color>
    <color name="legacy_long_pressed_highlight">#ffffffff</color>

    <!-- General purpose colors for Holo-themed elements -->
    <eat-comment />

    <!-- A light Holo shade of blue -->
    <color name="holo_blue_light">#ff33b5e5</color>
    <!-- A light Holo shade of gray -->
    <color name="holo_gray_light">#33999999</color>
    <!-- A light Holo shade of green -->
    <color name="holo_green_light">#ff99cc00</color>
    <!-- A light Holo shade of red -->
    <color name="holo_red_light">#ffff4444</color>
    <!-- A dark Holo shade of blue -->
    <color name="holo_blue_dark">#ff0099cc</color>
    <!-- A dark Holo shade of green -->
    <color name="holo_green_dark">#ff669900</color>
    <!-- A dark Holo shade of red -->
    <color name="holo_red_dark">#ffcc0000</color>
    <!-- A Holo shade of purple -->
    <color name="holo_purple">#ffaa66cc</color>
    <!-- A light Holo shade of orange -->
    <color name="holo_orange_light">#ffffbb33</color>
    <!-- A dark Holo shade of orange -->
    <color name="holo_orange_dark">#ffff8800</color>
    <!-- A really bright Holo shade of blue -->
    <color name="holo_blue_bright">#ff00ddff</color>
    <!-- A really bright Holo shade of gray -->
    <color name="holo_gray_bright">#33CCCCCC</color>

    <drawable name="notification_template_icon_bg">#3333B5E5</drawable>
    <drawable name="notification_template_icon_low_bg">#0cffffff</drawable>

    <!-- Keyguard colors -->
    <color name="keyguard_avatar_frame_color">#ffffffff</color>
    <color name="keyguard_avatar_frame_shadow_color">#80000000</color>
    <color name="keyguard_avatar_nick_color">#ffffffff</color>
    <color name="keyguard_avatar_frame_pressed_color">#ff35b5e5</color>

    <color name="accessibility_focus_highlight">#80ffff00</color>

How to kill an application with all its activities?

When the user wishes to exit all open activities, they should press a button which loads the first Activity that runs when your app starts, in my case "LoginActivity".

Intent intent = new Intent(getApplicationContext(), LoginActivity.class);
intent.putExtra("EXIT", true);

The above code clears all the activities except for LoginActivity. LoginActivity is the first activity that is brought up when the user runs the program. Then put this code inside the LoginActivity's onCreate, to signal when it should self destruct when the 'Exit' message is passed.

    if (getIntent().getBooleanExtra("EXIT", false)) {

The answer you get to this question from the Android platform is: "Don't make an exit button. Finish activities the user no longer wants, and the Activity manager will clean them up as it sees fit."

How to hide a View programmatically?

Try this:


Android Studio 3.0 Flavor Dimension Issue

Here you can resolve this issue, you need to add flavorDimension with productFlavors's name and need to define dimension as well, see below example and for more information see here

flavorDimensions 'yourAppName' //here defined dimensions
productFlavors {
    production {
        dimension 'yourAppName' //you just need to add this line
        //here you no need to write applicationIdSuffix because by default it will point to your app package which is also available inside manifest.xml file.


    staging {
        dimension 'yourAppName' //added here also
        applicationIdSuffix ".staging"//(.staging) will be added after your default package name.
        //or you can also use applicationId="your_package_name.staging" instead of applicationIdSuffix but remember if you are using applicationId then You have to mention full package name.
        //versionNameSuffix "-staging"


    develop {
        dimension 'yourAppName' //add here too
        applicationIdSuffix ".develop"
        //versionNameSuffix "-develop"


Import Google Play Services library in Android Studio






Font size of TextView in Android application changes on changing font size from native settings

You can use this code:


it solves your problem but you must know that you should respect user decisions. by this, changing text size from device settings will not change this value. so that's why you need to use sp instead of dp. So my suggestion is to review your app with different system font sizes(small,normal,big,...)

How to use support FileProvider for sharing content to other apps?

Fully working code sample how to share file from inner app folder. Tested on Android 7 and Android 5.




<?xml version="1.0" encoding="utf-8"?>

Code itself

    File imagePath = new File(getFilesDir(), "external_files");
    File imageFile = new File(imagePath.getPath(), "test.jpg");

    // Write data in your file

    Uri uri = FileProvider.getUriForFile(this, getPackageName(), imageFile);

    Intent intent = ShareCompat.IntentBuilder.from(this)
                .setStream(uri) // uri from FileProvider
                .setAction(Intent.ACTION_VIEW) //Change if needed
                .setDataAndType(uri, "image/*")


Button button = findViewById( always resolves to null in Android Studio

This is because findViewById() searches in the activity_main layout, while the button is located in the fragment's layout fragment_main.

Move that piece of code in the onCreateView() method of the fragment:


View rootView = inflater.inflate(R.layout.fragment_main, container, false);
Button buttonClick = (Button)rootView.findViewById(;
buttonClick.setOnClickListener(new View.OnClickListener() {
    public void onClick(View view) {
        onButtonClick((Button) view);

Notice that now you access it through rootView view:

Button buttonClick = (Button)rootView.findViewById(;

otherwise you would get again NullPointerException.

How to add (vertical) divider to a horizontal LinearLayout?

It is easy to add divider to layout, we don't need a separate view.

    android:weightSum="2" ></LinearLayout>

Above code make vertical divider for LinearLayout

Android - How to get application name? (Not package name)

The source comment added to NonLocalizedLabel directs us now to:

return context.getPackageManager().getApplicationLabelFormatted(context.getApplicationInfo());

How to read an http input stream

a complete code for reading from a webservice in two ways

public void buttonclick(View view) {
    // the name of your webservice where reactance is your method
    new GetMethodDemo().execute("");

public class GetMethodDemo extends AsyncTask<String, Void, String> {
    //see also: 
    //writing to see:
    String server_response;
    protected String doInBackground(String... strings) {
        URL url;
        HttpURLConnection urlConnection = null;
        try {
            url = new URL(strings[0]);
            urlConnection = (HttpURLConnection) url.openConnection();
            int responseCode = urlConnection.getResponseCode();
            if (responseCode == HttpURLConnection.HTTP_OK) {
                server_response = readStream(urlConnection.getInputStream());
                Log.v("CatalogClient", server_response);
        } catch (MalformedURLException e) {
        } catch (IOException e) {

        try {
            url = new URL(strings[0]);
            urlConnection = (HttpURLConnection) url.openConnection();
            BufferedReader in = new BufferedReader(new InputStreamReader(
            String inputLine;
            while ((inputLine = in.readLine()) != null)
            Log.v("bufferv ", server_response);
        } catch (MalformedURLException e) {
        } catch (IOException e) {
        return null;

    protected void onPostExecute(String s) {
        Log.e("Response", "" + server_response);
   //assume there is a field with id editText
        EditText editText = (EditText) findViewById(;

How to use SharedPreferences in Android to store, fetch and edit values

Basic idea of SharedPreferences is to store things on XML file.

  1. Declare your xml file path.(if you don't have this file, Android will create it. If you have this file, Android will access it.)

    SharedPreferences prefs = this.getSharedPreferences("", Context.MODE_PRIVATE);
  2. Write value to Shared Preferences

    prefs.edit().putLong("preference_file_key", 1010101).apply();

    the preference_file_key is the name of shared preference files. And the 1010101 is the value you need to store.

    apply() at last is to save the changes. If you get error from apply(), change it to commit(). So this alternative sentence is

    prefs.edit().putLong("preference_file_key", 1010101).commit();
  3. Read from Shared Preferences

    SharedPreferences sp = this.getSharedPreferences("", Context.MODE_PRIVATE);
    long lsp = sp.getLong("preference_file_key", -1);

    lsp will be -1 if preference_file_key has no value. If 'preference_file_key' has a value, it will return the value of this.

The whole code for writing is

    SharedPreferences prefs = this.getSharedPreferences("", Context.MODE_PRIVATE);    // Declare xml file
    prefs.edit().putLong("preference_file_key", 1010101).apply();    // Write the value to key.

The code for reading is

    SharedPreferences sf = this.getSharedPreferences("", Context.MODE_PRIVATE);    // Declare xml file
    long lsp = sp.getLong("preference_file_key", -1);    // Read the key and store in lsp

How to set timer in android?

If you have delta time already.

public class Timer {
    private float lastFrameChanged;
    private float frameDuration;
    private Runnable r;

    public Timer(float frameDuration, Runnable r) {
        this.frameDuration = frameDuration;
        this.lastFrameChanged = 0;
        this.r = r;

    public void update(float dt) {
        lastFrameChanged += dt;

        if (lastFrameChanged > frameDuration) {
            lastFrameChanged = 0;

Android Endless List

I've been working in another solution very similar to that, but, I am using a footerView to give the possibility to the user download more elements clicking the footerView, I am using a "menu" which is shown above the ListView and in the bottom of the parent view, this "menu" hides the bottom of the ListView, so, when the listView is scrolling the menu disappear and when scroll state is idle, the menu appear again, but when the user scrolls to the end of the listView, I "ask" to know if the footerView is shown in that case, the menu doesn't appear and the user can see the footerView to load more content. Here the code:


listView.setOnScrollListener(new OnScrollListener() {

    public void onScrollStateChanged(AbsListView view, int scrollState) {
        // TODO Auto-generated method stub
        if(scrollState == SCROLL_STATE_IDLE) {
            if(footerView.isShown()) {
            } else {
            } else {

    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {


How to set dropdown arrow in spinner?

dummy.xml (drawable should be of very less size. i have taken 24dp)

<?xml version="1.0" encoding="utf-8"?>
<layer-list android:opacity="transparent" xmlns:android="">
            <item android:width="100dp" android:gravity="right" android:start="300dp">
                <bitmap android:src="@drawable/down_button_dummy_dummy" android:gravity="center"/>

layout file snippet



click here to see resultant rendered layout

Android Studio installation on Windows 7 fails, no JDK found

To complete this stack of possible solutions: For me the problem was, that I did not execute the Android-Studio-Setup as administrator. Running it as administrator then made me able to install Android-Studio.

Manually put files to Android emulator SD card

In Visual Studio 2019 (Xamarin):

  1. Click on the Device Monitor (DDMS) button.

enter image description here

  1. Go to the File Explorer tab and click the button with a phone and a right-pointing arrow on top of it.

enter image description here

How to add headers to OkHttp request interceptor?

you can do it this way

private String GET(String url, Map<String, String> header) throws IOException {
        Headers headerbuild = Headers.of(header);
        Request request = new Request.Builder().url(url).headers(headerbuild).

        Response response = client.newCall(request).execute();
        return response.body().string();

How to display both icon and title of action inside ActionBar?

'always|withText' will work if there is sufficient room, otherwise it will only place icon. You can test it on your phone with rotation.

<item android:id="@id/menu_item"
android:showAsAction="always|withText" />

':app:lintVitalRelease' error when generating signed apk

Go to build.gradle(Module:app)

lintOptions {
    checkReleaseBuilds false
    // Or, if you prefer, you can continue to check for errors in release builds,
    // but continue the build even when errors are found:
    abortOnError false

How to check if activity is in foreground or in visible background?

Use the time gap between pause and resume from background to determine whether it is awake from background

In Custom Application

private static boolean isInBackground;
private static boolean isAwakeFromBackground;
private static final int backgroundAllowance = 10000;

public static void activityPaused() {
    isInBackground = true;
    final Handler handler = new Handler();
    handler.postDelayed(new Runnable() {
        public void run() {
            if (isInBackground) {
                isAwakeFromBackground = true;
    }, backgroundAllowance);
    Log.v("activity status", "activityPaused");

public static void activityResumed() {
    isInBackground = false;
        // do something when awake from background
        Log.v("activity status", "isAwakeFromBackground");
    isAwakeFromBackground = false;
    Log.v("activity status", "activityResumed");

In BaseActivity Class

protected void onResume() {

protected void onPause() {

Not Able To Debug App In Android Studio

This worked for me in Android Studio 3.6.3

Settings -> Build, Execution, Deployment -> Debugger -> Android Debug Bridge -> Enable 'Use libs backend'

enter image description here

How to increase heap size of an android application?

Use second process. Declare at AndroidManifest new Service with


Exchange between first and second process over BroadcastReceiver

Application Error - The connection to the server was unsuccessful. (file:///android_asset/www/index.html)

I had the same on my project.

I tried " super.setIntegerProperty("loadUrlTimeoutValue", 70000); " but to no avail.

I ensured all files were linked properly [ CSS, JS files etc ], validated the HTML using w3c validator [ ] , and cleaned the project [ Project -> Clean ]

It now loads and executes without the same error.

Hope this helps

Sending images using Http Post

Version 4.3.5 Updated Code

  • httpclient-4.3.5.jar
  • httpcore-4.3.2.jar
  • httpmime-4.3.5.jar

Since MultipartEntity has been deprecated. Please see the code below.

String responseBody = "failure";
HttpClient client = new DefaultHttpClient();
client.getParams().setParameter(CoreProtocolPNames.PROTOCOL_VERSION, HttpVersion.HTTP_1_1);

String url = WWPApi.URL_USERS;
Map<String, String> map = new HashMap<String, String>();
map.put("user_id", String.valueOf(userId));
map.put("action", "update");
url = addQueryParams(map, url);

HttpPost post = new HttpPost(url);
post.addHeader("Accept", "application/json");

MultipartEntityBuilder builder = MultipartEntityBuilder.create();

if (career != null)
    builder.addTextBody("career", career, ContentType.create("text/plain", MIME.UTF8_CHARSET));
if (gender != null)
    builder.addTextBody("gender", gender, ContentType.create("text/plain", MIME.UTF8_CHARSET));
if (username != null)
    builder.addTextBody("username", username, ContentType.create("text/plain", MIME.UTF8_CHARSET));
if (email != null)
    builder.addTextBody("email", email, ContentType.create("text/plain", MIME.UTF8_CHARSET));
if (password != null)
    builder.addTextBody("password", password, ContentType.create("text/plain", MIME.UTF8_CHARSET));
if (country != null)
    builder.addTextBody("country", country, ContentType.create("text/plain", MIME.UTF8_CHARSET));
if (file != null)
    builder.addBinaryBody("Filedata", file, ContentType.MULTIPART_FORM_DATA, file.getName());


try {
    responseBody = EntityUtils.toString(client.execute(post).getEntity(), "UTF-8");
//  System.out.println("Response from Server ==> " + responseBody);

    JSONObject object = new JSONObject(responseBody);
    Boolean success = object.optBoolean("success");
    String message = object.optString("error");

    if (!success) {
        responseBody = message;
    } else {
        responseBody = "success";

} catch (Exception e) {
} finally {

How to get screen width and height

below answer support api level below and above 10

 if (Build.VERSION.SDK_INT >= 11) {
            Point size = new Point();
            try {
                screenWidth = size.x;
                screenHeight = size.y;
            } catch (NoSuchMethodError e) {
                 screenHeight = this.getWindowManager().getDefaultDisplay().getHeight();

        } else {
            DisplayMetrics metrics = new DisplayMetrics();
            screenWidth = metrics.widthPixels;
            screenHeight = metrics.heightPixels;

How to stop EditText from gaining focus at Activity startup in Android

If you want to hide the keyboard at the start of the activity. Then mention


To that activity in the manifest file. Problem gets solved.


How do I add a newline to a TextView in Android?

You need to put \n in the file string.xml

<string name="strtextparkcar">press Park my Car to store location \n</string>

Gson library in Android Studio

Read Google-gson

Gson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object.

Add the following line to your MODULE LEVEL build.gradle configuration:

dependencies {
     implementation '' // Old 2.8.2

SQLiteDatabase.query method

if your SQL query is like this

SELECT col-1, col-2 FROM tableName WHERE col-1=apple,col-2=mango
GROUPBY col-3 HAVING Count(col-4) > 5  ORDERBY col-2 DESC LIMIT 15;

Then for query() method, we can do as:-

String table = "tableName";
String[] columns = {"col-1", "col-2"};
String selection = "col-1 =? AND col-2=?";       
String[] selectionArgs = {"apple","mango"};
String groupBy =col-3;
String having =" COUNT(col-4) > 5";
String orderBy = "col-2 DESC";
String limit = "15";

query(tableName, columns, selection, selectionArgs, groupBy, having, orderBy, limit);

Button Listener for button in fragment in android

Try this :

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;

public class FragmentOne extends Fragment{

    View rootView;        

public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

        rootView = inflater.inflate(R.layout.fragment_one, container, false);

        Button button = (Button) rootView.findViewById(;
        button.setOnClickListener(new View.OnClickListener()
            public void onClick(View v)
        return rootView;

  public void onButtonClicked(View view)
          //do your stuff here..           
    final FragmentTransaction ft = getFragmentManager().beginTransaction(); 
    ft.replace(, new FragmentTwo(), "NewFragmentTag"); 


check this : click here

notifyDataSetChanged example

For an ArrayAdapter, notifyDataSetChanged only works if you use the add(), insert(), remove(), and clear() on the Adapter.

When an ArrayAdapter is constructed, it holds the reference for the List that was passed in. If you were to pass in a List that was a member of an Activity, and change that Activity member later, the ArrayAdapter is still holding a reference to the original List. The Adapter does not know you changed the List in the Activity.

Your choices are:

  1. Use the functions of the ArrayAdapter to modify the underlying List (add(), insert(), remove(), clear(), etc.)
  2. Re-create the ArrayAdapter with the new List data. (Uses a lot of resources and garbage collection.)
  3. Create your own class derived from BaseAdapter and ListAdapter that allows changing of the underlying List data structure.
  4. Use the notifyDataSetChanged() every time the list is updated. To call it on the UI-Thread, use the runOnUiThread() of Activity. Then, notifyDataSetChanged() will work.

Clear back stack using fragments

Accepted answer was not enough for me. I had to use :

FragmentManager fm = getSupportFragmentManager();
int count = fm.getBackStackEntryCount();
for(int i = 0; i < count; ++i) {

How to change Android usb connect mode to charge only?

In your phone go to Settings->Connect to PC.

There you will see the option Default Connection Type. Select it and set it to your preference.

Drawing a line/path on Google Maps

Simply get route form this url and do next ...

Origin ---> starting point latitude & longitude

Destination---> ending point latitude & longitude

here i have put origin as Delhi latitude and longitude & destination as chandigarh latitude longitude,77.102493&destination=30.733315,76.779419&sensor=false&key="PUT YOUR MAP API KEY"

How to draw a line in android

To improve on the answers provided by @Janusz

I added this to my styles:

<style name="Divider">
    <item name="android:layout_width">match_parent</item>
    <item name="android:layout_height">1dp</item>
    <item name="android:background">?android:attr/listDivider</item>

Then in my layouts is less code and simpler to read.

<View style="@style/Divider"/>

if you want to do horizontal line spacing then do the above.

And for vertical line between two Views you have to replace android:layout_width parameters(attributes) with android:layout_height

How to disable EditText in Android

According to me...if you have already declared the edittext in the XML file and set the property in the XML file "android:enabled=false" and disable at runtime to it at that time in java file adding only 2 or 3 lines

  1. First create the object
  2. Declare EditText et1;
  3. Get by id

    et1 = (EditText) FindViewById(;

You can do enable or disable to every control at run time by java file and design time by XML file.

Notification not showing in Oreo

public class MyFirebaseMessagingServices extends FirebaseMessagingService {
    private NotificationChannel mChannel;
    private NotificationManager notifManager;
    public void onMessageReceived(RemoteMessage remoteMessage) {
        if (remoteMessage.getData().size() > 0) {
            try {
                JSONObject jsonObject = new JSONObject(remoteMessage.getData());
                displayCustomNotificationForOrders(jsonObject.getString("title"), jsonObject.getString("description"));
            } catch (JSONException e) {

    private void displayCustomNotificationForOrders(String title, String description) {
        if (notifManager == null) {
            notifManager = (NotificationManager) getSystemService
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationCompat.Builder builder;
            Intent intent = new Intent(this, Dashboard.class);
            PendingIntent pendingIntent;
            int importance = NotificationManager.IMPORTANCE_HIGH;
            if (mChannel == null) {
                mChannel = new NotificationChannel
                        ("0", title, importance);
            builder = new NotificationCompat.Builder(this, "0");

            intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP |
            pendingIntent = PendingIntent.getActivity(this, 1251, intent, PendingIntent.FLAG_ONE_SHOT);
                    .setSmallIcon(getNotificationIcon()) // required
                    .setContentText(description)  // required
                            (getResources(), R.mipmap.logo))
            Notification notification =;
            notifManager.notify(0, notification);
        } else {

            Intent intent = new Intent(this, Dashboard.class);
            PendingIntent pendingIntent = null;

            pendingIntent = PendingIntent.getActivity(this, 1251, intent, PendingIntent.FLAG_ONE_SHOT);

            Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
            NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
                    .setColor(ContextCompat.getColor(getBaseContext(), R.color.colorPrimary))
                    .setStyle(new NotificationCompat.BigTextStyle().setBigContentTitle(title).bigText(description));

            NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

    private int getNotificationIcon() {
        boolean useWhiteIcon = (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP);
        return useWhiteIcon ? R.mipmap.logo : R.mipmap.logo;

rawQuery(query, selectionArgs)

String mQuery = "SELECT Name,Family From tblName";
Cursor mCur = db.rawQuery(mQuery, new String[]{});
while ( !mCur.isAfterLast()) {
        String name= mCur.getString(mCur.getColumnIndex("Name"));
        String family= mCur.getString(mCur.getColumnIndex("Family"));

Name and family are your result

Unfortunately MyApp has stopped. How can I solve this?

People make mistakes, and so coding as well.

When ever any error happened, always check with the logcat with the text in red color however u can find out the real problem in blue color text with underline in those red color text.

Make sure if u create a new activity, always declare the activity in the AndroidManifest file.

If adding Permission, declare it in the AndroidMainifest file as well.

Retrieving Android API version programmatically

Got it. Its using the getApplicationInfo() method of the Context class.

Android : difference between invisible and gone?


This view is invisible, but it still takes up space for layout purposes.


This view is invisible, and it doesn't take any space for layout purposes.

Android Studio doesn't recognize my device

Although my computer could recognise my phone, I had to install the official drivers from the Samsung developer site to get adb/Android Studio to recognise it:

Samsung Android USB Driver for Windows

android on Text Change Listener

Add background dynamically in onCreate method:


also remove background from XML.

Default Activity not found in Android Studio

In my case, it worked when I removed the .idea folder from the project (Project/.ida) and re-opened Android Studio again.

Android Text over image

Try the below code this will help you`



        android:text="Juneja Art Gallery"

How to check if Location Services are enabled?

Yes you can check below is the code:

public boolean isGPSEnabled(Context mContext) 
    LocationManager lm = (LocationManager)
    return lm.isProviderEnabled(LocationManager.GPS_PROVIDER);

with the permission in the manifest file:

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

How to set margin of ImageView using code, not xml

Using a method similar to this might save you some headaches in some situations. If you have two passes of programmatical tinkering with margins it is safer to check if there are already some layoutParams set. If there are some margins already one should increase them and not replace them:

public void addMargins(View v, int left, int top, int right, int bottom) {
    LinearLayout.LayoutParams params = (LinearLayout.LayoutParams) v.getLayoutParams();
    if (params == null)
        params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,
    int oldLeft = params.leftMargin;
    int oldTop = params.topMargin;
    int oldRight = params.rightMargin;
    int oldBottom = params.bottomMargin;
    params.setMargins(oldLeft + left, oldTop + top, oldRight + right, oldBottom + bottom);

Scrollview vertical and horizontal in android

Since this seems to be the first search result in Google for "Android vertical+horizontal ScrollView", I thought I should add this here. Matt Clark has built a custom view based on the Android source, and it seems to work perfectly: Two Dimensional ScrollView

Beware that the class in that page has a bug calculating the view's horizonal width. A fix by Manuel Hilty is in the comments:

Solution: Replace the statement on line 808 by the following:

final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED);

Edit: The Link doesn't work anymore but here is a link to an old version of the blogpost.

Deleting Row in SQLite in Android

You can try like this:

 //---deletes a particular title---
public boolean deleteTitle(String name) 
    return db.delete(DATABASE_TABLE, KEY_NAME + "=" + name, null) > 0;


public boolean deleteTitle(String name) 
    return db.delete(DATABASE_TABLE, KEY_NAME + "=?", new String[]{name}) > 0;

How to use custom font in a project written in Android Studio

With Support Library 26.0 (and Android O) fonts can be loaded from resource easily with: enter image description here

Typeface typeface = ResourcesCompat.getFont(Context context, int fontResourceId) 

Docs for the method.

More info can be found here.

How to disable keypad popup when on edittext?

I found the following pattern to work well for me in code where I want to show a dialog to get the input (e.g., the string displayed in the text field is the result of selections made from a list of checkboxes in a dialog, rather than text entered via the keyboard).

  1. Disable soft input focus on the edit field. I can't disable for the entire activity, as there are edit fields I do want the keyboard to be used for in the same layout.
  2. Initial clicks in the text field yield a focus change, a repeated click yields a click event. So I override both (here I don't refactor the code out to illustrate both handlers do the same thing):

    tx = (TextView) m_activity.findViewById(;
    if (tx != null) {
        tx.setOnFocusChangeListener(new View.OnFocusChangeListener() {
            public void onFocusChange(View view, boolean hasFocus) {
                if (hasFocus) {
                    MedicationsListDialogFragment mld = new MedicationsListDialogFragment();
          , "Allergy Medications Dialog");
        tx.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                MedicationsListDialogFragment mld = new MedicationsListDialogFragment();
      , "Allergy Medications Dialog");

Set the absolute position of a view

Just in case it may help somebody, you may also try this animator ViewPropertyAnimator as below



Note: This pixel is not relative to the view. This pixel is the pixel position in the screen.

credits to bpr10 answer

Emulate Samsung Galaxy Tab

If you are developing on Netbeans, you will not get the Third-Party add-ons. You can download the Skins directly from Samsung here:

After download, unzip to ...\Android\android-sdk\add-ons[name of device]

Restart the Android SDK Manager, and the new device should be there under Extras.

It would be better to add the download site directly to the SDK...if anyone knows it, please post it.


Android. Fragment getActivity() sometimes returns null

The best to get rid of this is to keep activity reference when onAttach is called and use the activity reference wherever needed, for e.g.

public void onAttach(Context context) {
    mContext = context;

public void onDetach() {
    mContext = null;

Edited, since onAttach(Activity) is depreciated & now onAttach(Context) is being used

How to play videos in android from assets folder or raw folder?


AssetFileDescriptor afd = getAssets().openFd(fileName);
player.setDataSource(afd.getFileDescriptor(),afd.getStartOffset(), afd.getLength());

Load HTML file into WebView

probably this sample could help:

  WebView lWebView = (WebView)findViewById(;
  File lFile = new File(Environment.getExternalStorageDirectory() + "<FOLDER_PATH_TO_FILE>/<FILE_NAME>");
  lWebView.loadUrl("file:///" + lFile.getAbsolutePath());

How to use data-binding with Fragment

If you are using ViewModel and LiveData This is the sufficient syntax

Kotlin Syntax:

override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    return MartianDataBinding.inflate(
    ).apply {
        lifecycleOwner = viewLifecycleOwner
        vm = viewModel    // Attach your view model here

How to click or tap on a TextView text

You can use TextWatcher for TextView, is more flexible than ClickLinstener (not best or worse, only more one way).

holder.bt_foo_ex.addTextChangedListener(new TextWatcher() {

        public void onTextChanged(CharSequence s, int start, int before, int count) {
            // code during!


        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            // code before!


        public void afterTextChanged(Editable s) {
            // code after!


adb shell command to make Android package uninstall dialog appear

You can do it from adb using this command:

adb shell am start -a android.intent.action.DELETE -d package:<your app package>

Work with a time span in Javascript

 * ??????????????,???????? 
 * English: Calculating the difference between the given time and the current time and then showing the results.
function date2Text(date) {
    var milliseconds = new Date() - date;
    var timespan = new TimeSpan(milliseconds);
    if (milliseconds < 0) {
        return timespan.toString() + "??";
        return timespan.toString() + "?";

 * ???????????
 * English: Using a function to calculate the time interval
 * @param milliseconds ???
var TimeSpan = function (milliseconds) {
    milliseconds = Math.abs(milliseconds);
    var days = Math.floor(milliseconds / (1000 * 60 * 60 * 24));
    milliseconds -= days * (1000 * 60 * 60 * 24);

    var hours = Math.floor(milliseconds / (1000 * 60 * 60));
    milliseconds -= hours * (1000 * 60 * 60);

    var mins = Math.floor(milliseconds / (1000 * 60));
    milliseconds -= mins * (1000 * 60);

    var seconds = Math.floor(milliseconds / (1000));
    milliseconds -= seconds * (1000);
    return {
        getDays: function () {
            return days;
        getHours: function () {
            return hours;
        getMinuts: function () {
            return mins;
        getSeconds: function () {
            return seconds;
        toString: function () {
            var str = "";
            if (days > 0 || str.length > 0) {
                str += days + "?";
            if (hours > 0 || str.length > 0) {
                str += hours + "??";
            if (mins > 0 || str.length > 0) {
                str += mins + "??";
            if (days == 0 && (seconds > 0 || str.length > 0)) {
                str += seconds + "?";
            return str;

Swift UIView background color opacity

Setting alpha property of a view affects its subviews. If you want just transparent background set view's backgroundColor proprty to a color that has alpha component smaller than 1.

view.backgroundColor = UIColor.white.withAlphaComponent(0.5)

How to set text size in a button in html

Try this, its working in FF

button {
 font-family: Arial,Helvetica,sans-serif;
 font-size: 14px;

Is there a simple way to remove multiple spaces in a string?

I have to agree with Paul McGuire's comment. To me,

' '.join(the_string.split())

is vastly preferable to whipping out a regex.

My measurements (Linux and Python 2.5) show the split-then-join to be almost five times faster than doing the "re.sub(...)", and still three times faster if you precompile the regex once and do the operation multiple times. And it is by any measure easier to understand -- much more Pythonic.

How can I use JQuery to post JSON data?

You're passing an object, not a JSON string. When you pass an object, jQuery uses $.param to serialize the object into name-value pairs.

If you pass the data as a string, it won't be serialized:

    type: 'POST',
    url: '/form/',
    data: '{"name":"jonas"}', // or JSON.stringify ({name: 'jonas'}),
    success: function(data) { alert('data: ' + data); },
    contentType: "application/json",
    dataType: 'json'

How do I fetch lines before/after the grep result in bash?

You can use the -B and -A to print lines before and after the match.

grep -i -B 10 'error' data

Will print the 10 lines before the match, including the matching line itself.

How to get a list of all files in Cloud Storage in a Firebase app?

Since Firebase SDKs for JavaScript release 6.1, iOS release 6.4, and Android release version 18.1 all have a method to list files.

The documentation is a bit sparse so far, so I recommend checking out Rosário's answer for details.

Previous answer, since this approach can still be useful at times:

There currently is no API call in the Firebase SDK to list all files in a Cloud Storage folder from within an app. If you need such functionality, you should store the metadata of the files (such as the download URLs) in a place where you can list them. The Firebase Realtime Database and Cloud Firestore are perfect for this and allows you to also easily share the URLs with others.

You can find a good (but somewhat involved) sample of this in our FriendlyPix sample app. The relevant code for the web version is here, but there are also versions for iOS and Android.

PHP: How to use array_filter() to filter array keys?

PHP 5.6 introduced a third parameter to array_filter(), flag, that you can set to ARRAY_FILTER_USE_KEY to filter by key instead of value:

$my_array = ['foo' => 1, 'hello' => 'world'];
$allowed  = ['foo', 'bar'];
$filtered = array_filter(
    function ($key) use ($allowed) {
        return in_array($key, $allowed);

Clearly this isn't as elegant as array_intersect_key($my_array, array_flip($allowed)), but it does offer the additional flexibility of performing an arbitrary test against the key, e.g. $allowed could contain regex patterns instead of plain strings.

You can also use ARRAY_FILTER_USE_BOTH to have both the value and the key passed to your filter function. Here's a contrived example based upon the first, but note that I'd not recommend encoding filtering rules using $allowed this way:

$my_array = ['foo' => 1, 'bar' => 'baz', 'hello' => 'wld'];
$allowed  = ['foo' => true, 'bar' => true, 'hello' => 'world'];
$filtered = array_filter(
    function ($val, $key) use ($allowed) { // N.b. $val, $key not $key, $val
        return isset($allowed[$key]) && (
            $allowed[$key] === true || $allowed[$key] === $val
); // ['foo' => 1, 'bar' => 'baz']

How to place div side by side

You can use CSS grid to achieve this, this is the long-hand version for the purposes of illustration:

div.container {_x000D_
    display: grid;_x000D_
    grid-template-columns: 220px 20px auto;_x000D_
    grid-template-rows: auto;_x000D_
div.left {_x000D_
    grid-column-start: 1;_x000D_
    grid-column-end: 2;_x000D_
    grid-row-start: row1-start_x000D_
    grid-row-end: 3;_x000D_
    background-color: Aqua;_x000D_
div.right {_x000D_
    grid-column-start: 3;_x000D_
    grid-column-end: 4;_x000D_
    grid-row-start: 1;_x000D_
    grid-row-end; 1;_x000D_
    background-color: Silver;_x000D_
div.below {_x000D_
    grid-column-start: 1;_x000D_
    grid-column-end: 4;_x000D_
    grid-row-start: 2;_x000D_
    grid-row-end; 2;_x000D_
<div class="container">_x000D_
    <div class="left">Left</div>_x000D_
    <div class="right">Right</div>_x000D_
    <div class="below">Below</div>_x000D_

Or the more traditional method using float and margin.

I have included a background colour in this example to help show where things are - and also what to do with content below the floated-area.

Don't put your styles inline in real life, extract them into a style sheet.

div.left {_x000D_
    width: 200px;_x000D_
    float: left;_x000D_
    background-color: Aqua;_x000D_
div.right {_x000D_
    margin-left: 220px;_x000D_
    background-color: Silver;_x000D_
div.clear {_x000D_
    clear: both;_x000D_
    <div class="left"> Left </div>_x000D_
    <div class="right"> Right </div>_x000D_
    <div class="clear">Below</div>

<div style="width: 200px; float: left; background-color: Aqua;"> Left </div>
<div style="margin-left: 220px; background-color: Silver;"> Right </div>
<div style="clear: both;">Below</div>

Best way to check if column returns a null value (from database to .net application)

Just check for

if(table.rows[0][0] == null)
     //Whatever I want to do

or you could

     //Whatever I want to do

How to align content of a div to the bottom

Relative+absolute positioning is your best bet:

#header {_x000D_
  position: relative;_x000D_
  min-height: 150px;_x000D_
#header-content {_x000D_
  position: absolute;_x000D_
  bottom: 0;_x000D_
  left: 0;_x000D_
#header, #header * {_x000D_
  background: rgba(40, 40, 100, 0.25);_x000D_
<div id="header">_x000D_
  <div id="header-content">Some content</div>_x000D_

But you may run into issues with that. When I tried it I had problems with dropdown menus appearing below the content. It's just not pretty.

Honestly, for vertical centering issues and, well, any vertical alignment issues with the items aren't fixed height, it's easier just to use tables.

Example: Can you do this HTML layout without using tables?

Why I can't change directories using "cd"?

It is an old question, but I am really surprised I don't see this trick here

Instead of using cd you can use

export PWD=the/path/you/want

No need to create subshells or use aliases.

Note that it is your responsibility to make sure the/path/you/want exists.

Printing Batch file results to a text file

For showing result of batch file in text file, you can use

this command

chdir > test.txt

This command will redirect result to test.txt.

When you open test.txt you will found current path of directory in test.txt

Call angularjs function using jquery/javascript

Another way is to create functions in global scope. This was necessary for me since it wasn't possible in Angular 1.5 to reach a component's scope.


angular.module("app", []).component("component", {_x000D_
  controller: ["$window", function($window) {_x000D_
    var self = this;_x000D_
    self.logg = function() {_x000D_
    $window.angularControllerLogg = self.logg;_x000D_

Is it possible to set a number to NaN or infinity?

Is it possible to set a number to NaN or infinity?

Yes, in fact there are several ways. A few work without any imports, while others require import, however for this answer I'll limit the libraries in the overview to standard-library and NumPy (which isn't standard-library but a very common third-party library).

The following table summarizes the ways how one can create a not-a-number or a positive or negative infinity float:

¦   result ¦ NaN          ¦ Infinity           ¦ -Infinity          ¦
¦ module   ¦              ¦                    ¦                    ¦
¦ built-in ¦ float("nan") ¦ float("inf")       ¦ -float("inf")      ¦
¦          ¦              ¦ float("infinity")  ¦ -float("infinity") ¦
¦          ¦              ¦ float("+inf")      ¦ float("-inf")      ¦
¦          ¦              ¦ float("+infinity") ¦ float("-infinity") ¦
¦ math     ¦ math.nan     ¦ math.inf           ¦ -math.inf          ¦
¦ cmath    ¦ cmath.nan    ¦ cmath.inf          ¦ -cmath.inf         ¦
¦ numpy    ¦ numpy.nan    ¦ numpy.PINF         ¦ numpy.NINF         ¦
¦          ¦ numpy.NaN    ¦ numpy.inf          ¦ -numpy.inf         ¦
¦          ¦ numpy.NAN    ¦ numpy.infty        ¦ -numpy.infty       ¦
¦          ¦              ¦ numpy.Inf          ¦ -numpy.Inf         ¦
¦          ¦              ¦ numpy.Infinity     ¦ -numpy.Infinity    ¦

A couple remarks to the table:

  • The float constructor is actually case-insensitive, so you can also use float("NaN") or float("InFiNiTy").
  • The cmath and numpy constants return plain Python float objects.
  • The numpy.NINF is actually the only constant I know of that doesn't require the -.
  • It is possible to create complex NaN and Infinity with complex and cmath:

    ¦   result ¦ NaN+0j         ¦ 0+NaNj          ¦ Inf+0j              ¦ 0+Infj               ¦
    ¦ module   ¦                ¦                 ¦                     ¦                      ¦
    ¦ built-in ¦ complex("nan") ¦ complex("nanj") ¦ complex("inf")      ¦ complex("infj")      ¦
    ¦          ¦                ¦                 ¦ complex("infinity") ¦ complex("infinityj") ¦
    ¦ cmath    ¦ cmath.nan ¹    ¦ cmath.nanj      ¦ cmath.inf ¹         ¦ cmath.infj           ¦

    The options with ¹ return a plain float, not a complex.

is there any function to check whether a number is infinity or not?

Yes there is - in fact there are several functions for NaN, Infinity, and neither Nan nor Inf. However these predefined functions are not built-in, they always require an import:

¦      for ¦ NaN         ¦ Infinity or    ¦ not NaN and        ¦
¦          ¦             ¦ -Infinity      ¦ not Infinity and   ¦
¦ module   ¦             ¦                ¦ not -Infinity      ¦
¦ math     ¦ math.isnan  ¦ math.isinf     ¦ math.isfinite      ¦
¦ cmath    ¦ cmath.isnan ¦ cmath.isinf    ¦ cmath.isfinite     ¦
¦ numpy    ¦ numpy.isnan ¦ numpy.isinf    ¦ numpy.isfinite     ¦

Again a couple of remarks:

  • The cmath and numpy functions also work for complex objects, they will check if either real or imaginary part is NaN or Infinity.
  • The numpy functions also work for numpy arrays and everything that can be converted to one (like lists, tuple, etc.)
  • There are also functions that explicitly check for positive and negative infinity in NumPy: numpy.isposinf and numpy.isneginf.
  • Pandas offers two additional functions to check for NaN: pandas.isna and pandas.isnull (but not only NaN, it matches also None and NaT)
  • Even though there are no built-in functions, it would be easy to create them yourself (I neglected type checking and documentation here):

    def isnan(value):
        return value != value  # NaN is not equal to anything, not even itself
    infinity = float("infinity")
    def isinf(value):
        return abs(value) == infinity 
    def isfinite(value):
        return not (isnan(value) or isinf(value))

To summarize the expected results for these functions (assuming the input is a float):

¦          input ¦ NaN   ¦ Infinity   ¦ -Infinity   ¦ something else   ¦
¦ function       ¦       ¦            ¦             ¦                  ¦
¦ isnan          ¦ True  ¦ False      ¦ False       ¦ False            ¦
¦ isinf          ¦ False ¦ True       ¦ True        ¦ False            ¦
¦ isfinite       ¦ False ¦ False      ¦ False       ¦ True             ¦

Is it possible to set an element of an array to NaN in Python?

In a list it's no problem, you can always include NaN (or Infinity) there:

>>> [math.nan, math.inf, -math.inf, 1]  # python list
[nan, inf, -inf, 1]

However if you want to include it in an array (for example array.array or numpy.array) then the type of the array must be float or complex because otherwise it will try to downcast it to the arrays type!

>>> import numpy as np
>>> float_numpy_array = np.array([0., 0., 0.], dtype=float)
>>> float_numpy_array[0] = float("nan")
>>> float_numpy_array
array([nan,  0.,  0.])

>>> import array
>>> float_array = array.array('d', [0, 0, 0])
>>> float_array[0] = float("nan")
>>> float_array
array('d', [nan, 0.0, 0.0])

>>> integer_numpy_array = np.array([0, 0, 0], dtype=int)
>>> integer_numpy_array[0] = float("nan")
ValueError: cannot convert float NaN to integer

Shell Scripting: Using a variable to define a path

Don't use spaces...


SPTH = '/home/Foo/Documents/Programs/ShellScripts/Butler'



IIS7: A process serving application pool 'YYYYY' suffered a fatal communication error with the Windows Process Activation Service

I ran into this recently. Our organization restricts the accounts that run application pools to a select list of servers in Active Directory. I found that I had not added one of the machines hosting the application to the "Log On To" list for the account in AD.

How do you explicitly set a new property on `window` in TypeScript?

Create a file called global.d.ts e.g /src/@types/global.d.ts then define an interface like:

interface Window {
  myLib: any


How to increase the distance between table columns in HTML?

A better solution than selected answer would be to use border-size rather than border-spacing. The main problem with using border-spacing is that even the first column would have a spacing in the front.

For example,

table {_x000D_
  border-collapse: separate;_x000D_
  border-spacing: 80px 0;_x000D_
td {_x000D_
  padding: 10px 0;_x000D_
    <td>First Column</td>_x000D_
    <td>Second Column</td>_x000D_
    <td>Third Column</td>_x000D_

To avoid this use: border-left: 100px solid #FFF; and set border:0px for the first column.

For example,

  border-left: 100px solid #FFF;_x000D_
 tr>td:first-child {_x000D_
<table id="t">_x000D_

What do parentheses surrounding an object/function/class declaration mean?

See this question. The first set of parenthesis aren't necessary if you use a function name, but a nameless function requires this construct and the parenthesis serve for coders to realize that they've viewing a self-invoking function when browsing the code (see one blogger's best-practices recommendation).

Selectors in Objective-C?

Selectors are an efficient way to reference methods directly in compiled code - the compiler is what actually assigns the value to a SEL.

Other have already covered the second part of your q, the ':' at the end matches a different signature than what you're looking for (in this case that signature doesn't exist).

Preventing scroll bars from being hidden for MacOS trackpad users in WebKit/Blink

Browser scrollbars don't work at all on iPhone/iPad. At work we are using custom JavaScript scrollbars like jScrollPane to provide a consistent cross-browser UI:

It works very well for me - you can make some really beautiful custom scrollbars that fit the design of your site.

Conditional logic in AngularJS template

You can use ng-show on every div element in the loop. Is this what you've wanted: ?

<div class="from" ng-show="message.from">From: {{}}</div>

How to serialize an object to XML without getting xmlns="..."?

Ahh... nevermind. It's always the search after the question is posed that yields the answer. My object that is being serialized is obj and has already been defined. Adding an XMLSerializerNamespace with a single empty namespace to the collection does the trick.

In VB like this:

Dim xs As New XmlSerializer(GetType(cEmploymentDetail))
Dim ns As New XmlSerializerNamespaces()
ns.Add("", "")

Dim settings As New XmlWriterSettings()
settings.OmitXmlDeclaration = True

Using ms As New MemoryStream(), _
    sw As XmlWriter = XmlWriter.Create(ms, settings), _
    sr As New StreamReader(ms)
xs.Serialize(sw, obj, ns)
ms.Position = 0
End Using

in C# like this:

//Create our own namespaces for the output
XmlSerializerNamespaces ns = new XmlSerializerNamespaces();

//Add an empty namespace and empty value
ns.Add("", "");

//Create the serializer
XmlSerializer slz = new XmlSerializer(someType);

//Serialize the object with our own namespaces (notice the overload)
slz.Serialize(myXmlTextWriter, someObject, ns);

In jQuery, what's the best way of formatting a number to 2 decimal places?

We modify a Meouw function to be used with keyup, because when you are using an input it can be more helpful.

Check this:

Hey there!, @heridev and I created a small function in jQuery.

You can try next:


<input type="text" name="one" class="two-digits"><br>
<input type="text" name="two" class="two-digits">?


// apply the two-digits behaviour to elements with 'two-digits' as their class
$( function() {
            if($(this).val().split(".")[1].length > 2){                
                if( isNaN( parseFloat( this.value ) ) ) return;
                this.value = parseFloat(this.value).toFixed(2);
         return this; //for chaining


(@heridev, @vicmaster)

SQL Server : fetching records between two dates?

Your question didnt ask how to use BETWEEN correctly, rather asked for help with the unexpectedly truncated results...

As mentioned/hinting at in the other answers, the problem is that you have time segments in addition to the dates.

In my experience, using date diff is worth the extra wear/tear on the keyboard. It allows you to express exactly what you want, and you are covered.

select * 
from xxx 
where datediff(d, '2012-10-26', dates) >=0
and  datediff(d, dates,'2012-10-27') >=0

using datediff, if the first date is before the second date, you get a positive number. There are several ways to write the above, for instance always having the field first, then the constant. Just flipping the operator. Its a matter of personal preference.

you can be explicit about whether you want to be inclusive or exclusive of the endpoints by dropping one or both equal signs.

BETWEEN will work in your case, because the endpoints are both assumed to be midnight (ie DATEs). If your endpoints were also DATETIME, using BETWEEN may require even more casting. In my mind DATEDIFF was put in our lives to insulate us from those issues.

Get div tag scroll position using JavaScript

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">
<html xmlns="">
<head runat="server">
    <script type="text/javascript">
        function scollPos() {
            var div = document.getElementById("myDiv").scrollTop;
            document.getElementById("pos").innerHTML = div;
    <form id="form1">
    <div id="pos">
    <div id="myDiv" style="overflow: auto; height: 200px; width: 200px;" onscroll="scollPos();">
        Place some large content here

Targeting both 32bit and 64bit with Visual Studio in same solution/project

You can use a condition to an ItemGroup for the dll references in the project file.
This will cause visual studio to recheck the condition and references whenever you change the active configuration.
Just add a condition for each configuration.


 <ItemGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|x86' ">
    <Reference Include="DLLName">
    <ProjectReference Include="..\MyOtherProject.vcxproj">

Why does python use 'else' after for and while loops?

I read it like "When the iterable is exhausted completely, and the execution is about to proceed to the next statement after finishing the for, the else clause will be executed." Thus, when the iteration is broken by break, this will not be executed.

How to upload files in core?

You can add a new property of type IFormFile to your view model

public class CreatePost
   public string ImageCaption { set;get; }
   public string ImageDescription { set;get; }
   public IFormFile MyImage { set; get; }

and in your GET action method, we will create an object of this view model and send to the view.

public IActionResult Create()
   return View(new CreatePost());

Now in your Create view which is strongly typed to our view model, have a form tag which has the enctype attribute set to "multipart/form-data"

@model CreatePost
<form asp-action="Create" enctype="multipart/form-data">   

    <input asp-for="ImageCaption"/>
    <input asp-for="ImageDescription"/>
    <input asp-for="MyImage"/>

    <input type="submit"/>

And your HttpPost action to handle the form posting

public IActionResult Create(CreatePost model)
   var img = model.MyImage;
   var imgCaption = model.ImageCaption;

   //Getting file meta data
   var fileName = Path.GetFileName(model.MyImage.FileName);
   var contentType = model.MyImage.ContentType;

   // do something with the above data
   // to do : return something

If you want to upload the file to some directory in your app, you should use IHostingEnvironment to get the webroot path. Here is a working sample.

public class HomeController : Controller
    private readonly IHostingEnvironment hostingEnvironment;
    public HomeController(IHostingEnvironment environment)
        hostingEnvironment = environment;
    public IActionResult Create(CreatePost model)
        // do other validations on your model as needed
        if (model.MyImage != null)
            var uniqueFileName = GetUniqueFileName(model.MyImage.FileName);
            var uploads = Path.Combine(hostingEnvironment.WebRootPath, "uploads");
            var filePath = Path.Combine(uploads,uniqueFileName);
            model.MyImage.CopyTo(new FileStream(filePath, FileMode.Create)); 

            //to do : Save uniqueFileName  to your db table   
        // to do  : Return something
        return RedirectToAction("Index","Home");
    private string GetUniqueFileName(string fileName)
        fileName = Path.GetFileName(fileName);
        return  Path.GetFileNameWithoutExtension(fileName)
                  + "_" 
                  + Guid.NewGuid().ToString().Substring(0, 4) 
                  + Path.GetExtension(fileName);

This will save the file to uploads folder inside wwwwroot directory of your app with a random file name generated using Guids ( to prevent overwriting of files with same name)

Here we are using a very simple GetUniqueName method which will add 4 chars from a guid to the end of the file name to make it somewhat unique. You can update the method to make it more sophisticated as needed.

Should you be storing the full url to the uploaded image in the database ?

No. Do not store the full url to the image in the database. What if tomorrow your business decides to change your company/product name from to ? Now you have to fix all the urls in the table!

What should you store ?

You should store the unique filename which you generated above(the uniqueFileName varibale we used above) to store the file name. When you want to display the image back, you can use this value (the filename) and build the url to the image.

For example, you can do this in your view.

    var imgFileName = "cats_46df.png";
<img src="~/uploads/@imgFileName"  alt="my img"/>

I just hardcoded an image name to imgFileName variable and used that. But you may read the stored file name from your database and set to your view model property and use that. Something like

<img src="~/uploads/@Model.FileName"  alt="my img"/>

Storing the image to table

If you want to save the file as bytearray/varbinary to your database, you may convert the IFormFile object to byte array like this

private byte[] GetByteArrayFromImage(IFormFile file)
    using (var target = new MemoryStream())
        return target.ToArray();

Now in your http post action method, you can call this method to generate the byte array from IFormFile and use that to save to your table. the below example is trying to save a Post entity object using entity framework.

public IActionResult Create(CreatePost model)
    //Create an object of your entity class and map property values
    var post=new Post() { ImageCaption = model.ImageCaption };

    if (model.MyImage != null)
       post.Image =  GetByteArrayFromImage(model.MyImage);
    return RedirectToAction("Index","Home");

Get user profile picture by Id" + facebookId + "/picture?type=square For instance:

There are also more sizes besides "square". See the docs.

Update September 2020
As Facebook have updated their docs this method is not working anymore without a token. You need to append some kind of access_token. You can find further information and how to do it correctly in the fb docs to the graph api of user picture

Requirements Change This endpoint supports App-Scoped User IDs (ASID), User IDs (UID), and Page-Scoped User IDs (PSID). Currently you can query ASIDs and UIDs with no requirements. However, beginning October 24, 2020, an access token will be required for all UID-based queries. If you query a UID and thus must include a token:

use a User access token for Facebook Login authenticated requests
use a Page access token for page-scoped requests
use an App access token for server-side requests
use a Client access token for mobile or web client-side requests

Quote of fb docs

Adding an onclicklistener to listview (android)

list.setOnItemSelectedListener(new OnItemSelectedListener() {

        public void onItemSelected(AdapterView<?> arg0, View arg1,
                int arg2, long arg3) {
            // TODO Auto-generated method stub


        public void onNothingSelected(AdapterView<?> arg0) {
            // TODO Auto-generated method stub


Bootstrap 4, How do I center-align a button?

Try this with bootstrap


<div class="row justify-content-center">
  <button type="submit" class="btn btn-primary">btnText</button>


How can I make window.showmodaldialog work in chrome 37?


It's deprecated by design. You can re-enable showModalDialog support, but only temporarily – until May of 2015. Use this time to create alternative solutions.

Here’s how to do it in Chrome for Windows. Open Registry Editor (regedit) and create following key:


Under the EnableDeprecatedWebPlatformFeatures key create a string value with name 1 and value of ShowModalDialog_EffectiveUntil20150430. To verify that the policy is enabled, visit chrome://policy URL.

UPDATE: If the above didn’t work for you here’s another method to try.

  1. Download Chrome ADM templates from
  2. Extract and import policy relevant to your locale (e.g. windows\adm\en-US\chrome.adm. You can import either via gpedit.mscor using these utilities on Home editions of windows:
  3. Under “Adminstrative Templates” locate Google Chrome template and enable “Enable Deprecated Web Platform Feautes”.
  4. Open the feature and add “ShowModalDialog_EffectiveUntil20150430" key.

Parcelable encountered IOException writing serializable object getactivity()

If you can't make DNode serializable a good solution would be to add "transient" to the variable.


public static transient DNode dNode = null;

This will ignore the variable when using Intent.putExtra(...).

ORA-00904: invalid identifier

I had the same exception in JPA 2 using eclipse link. I had an @embedded class with one to one relationship with an entity. By mistake ,in the embedded class, i had also the annotation @Table("TRADER"). When the DB was created by the JPA from the entities it also created a table TRADER (which was a wrong as the Trader entity was embedded to the main entity) and the existence of that table was causing the above exception every time i was trying to persist my entity. After deleting the TRADER table the exception disappered.

How to put a component inside another component in Angular2?

I think in your Angular-2 version directives are not supported in Component decorator, hence you have to register directive same as other component in @NgModule and then import in component as below and also remove directives: [ChildComponent] from decorator.

import {myDirective} from './myDirective';

startsWith() and endsWith() functions in PHP

If speed is important for you, try this.(I believe it is the fastest method)

Works only for strings and if $haystack is only 1 character

function startsWithChar($needle, $haystack)
   return ($needle === $haystack[0]);

function endsWithChar($needle, $haystack)
   return ($needle === $haystack[strlen($haystack) - 1]);

echo startsWithChar('|',$str); //Returns true
echo endsWithChar('}',$str); //Returns true
echo startsWithChar('=',$str); //Returns false
echo endsWithChar('#',$str); //Returns false

Format Float to n decimal places

Here's a quick sample using the DecimalFormat class mentioned by Nick.

float f = 12.345f;
DecimalFormat df = new DecimalFormat("#.00");

The output of the print statement will be 12.35. Notice that it will round it for you.

How to use gitignore command in git

So based on what you said, these files are libraries/documentation you don't want to delete but also don't want to push to github. Let say you have your project in folder your_project and a doc directory: your_project/doc.

  1. Remove it from the project directory (without actually deleting it): git rm --cached doc/*
  2. If you don't already have a .gitignore, you can make one right inside of your project folder: project/.gitignore.
  3. Put doc/* in the .gitignore
  4. Stage the file to commit: git add project/.gitignore
  5. Commit: git commit -m "message".
  6. Push your change to github.

How do Common Names (CN) and Subject Alternative Names (SAN) work together?

To be absolutely correct you should put all the names into the SAN field.

The CN field should contain a Subject Name not a domain name, but when the Netscape found out this SSL thing, they missed to define its greatest market. Simply there was not certificate field defined for the Server URL.

This was solved to put the domain into the CN field, and nowadays usage of the CN field is deprecated, but still widely used. The CN can hold only one domain name.

The general rules for this: CN - put here your main URL (for compatibility) SAN - put all your domain here, repeat the CN because its not in right place there, but its used for that...

If you found a correct implementation, the answers for your questions will be the followings:

  • Has this setup a special meaning, or any [dis]advantages over setting both CNs? You cant set both CNs, because CN can hold only one name. You can make with 2 simple CN certificate instead one CN+SAN certificate, but you need 2 IP addresses for this.

  • What happens on server-side if the other one, host.domain.tld, is being requested? It doesn't matter whats happen on server side.

In short: When a browser client connects to this server, then the browser sends encrypted packages, which are encrypted with the public key of the server. Server decrypts the package, and if server can decrypt, then it was encrypted for the server.

The server doesn't know anything from the client before decrypt, because only the IP address is not encrypted trough the connection. This is why you need 2 IPs for 2 certificates. (Forget SNI, there is too much XP out there still now.)

On client side the browser gets the CN, then the SAN until all of the are checked. If one of the names matches for the site, then the URL verification was done by the browser. (im not talking on the certificate verification, of course a lot of ocsp, crl, aia request and answers travels on the net every time.)

Add Header and Footer for PDF using iTextsharp

As already answered by @Bruno you need to use pageEvents.

Please check out the sample code below:

private void CreatePDF()
    string fileName = string.Empty;    
    DateTime fileCreationDatetime = DateTime.Now;    
    fileName = string.Format("{0}.pdf", fileCreationDatetime.ToString(@"yyyyMMdd") + "_" + fileCreationDatetime.ToString(@"HHmmss"));    
    string pdfPath = Server.MapPath(@"~\PDFs\") +   fileName;

    using (FileStream msReport = new FileStream(pdfPath, FileMode.Create))
        //step 1
        using (Document pdfDoc = new Document(PageSize.A4, 10f, 10f, 140f, 10f))
                // step 2
                PdfWriter pdfWriter = PdfWriter.GetInstance(pdfDoc, msReport);
                pdfWriter.PageEvent = new Common.ITextEvents();

                //open the stream 

                for (int i = 0; i < 10; i++)
                    Paragraph para = new Paragraph("Hello world. Checking Header Footer", new Font(Font.FontFamily.HELVETICA, 22));    
                    para.Alignment = Element.ALIGN_CENTER;    

            catch (Exception ex)
                //handle exception

And create one class file named ITextEvents.cs and add following code:

public class ITextEvents : PdfPageEventHelper
    // This is the contentbyte object of the writer
    PdfContentByte cb;

    // we will put the final number of pages in a template
    PdfTemplate headerTemplate, footerTemplate;

    // this is the BaseFont we are going to use for the header / footer
    BaseFont bf = null;

    // This keeps track of the creation time
    DateTime PrintTime = DateTime.Now;    

    #region Fields
    private string _header;

    #region Properties
    public string Header
        get { return _header; }
        set { _header = value; }

    public override void OnOpenDocument(PdfWriter writer, Document document)
            PrintTime = DateTime.Now;
            bf = BaseFont.CreateFont(BaseFont.HELVETICA, BaseFont.CP1252, BaseFont.NOT_EMBEDDED);
            cb = writer.DirectContent;
            headerTemplate = cb.CreateTemplate(100, 100);
            footerTemplate = cb.CreateTemplate(50, 50);
        catch (DocumentException de)
        catch (System.IO.IOException ioe)

    public override void OnEndPage(iTextSharp.text.pdf.PdfWriter writer, iTextSharp.text.Document document)
        base.OnEndPage(writer, document);    
        iTextSharp.text.Font baseFontNormal = new iTextSharp.text.Font(iTextSharp.text.Font.FontFamily.HELVETICA, 12f, iTextSharp.text.Font.NORMAL, iTextSharp.text.BaseColor.BLACK);    
        iTextSharp.text.Font baseFontBig = new iTextSharp.text.Font(iTextSharp.text.Font.FontFamily.HELVETICA, 12f, iTextSharp.text.Font.BOLD, iTextSharp.text.BaseColor.BLACK);    
        Phrase p1Header = new Phrase("Sample Header Here", baseFontNormal);

        //Create PdfTable object
        PdfPTable pdfTab = new PdfPTable(3);

        //We will have to create separate cells to include image logo and 2 separate strings
        //Row 1
        PdfPCell pdfCell1 = new PdfPCell();
        PdfPCell pdfCell2 = new PdfPCell(p1Header);
        PdfPCell pdfCell3 = new PdfPCell();
        String text = "Page " + writer.PageNumber + " of ";    

        //Add paging to header
            cb.SetFontAndSize(bf, 12);
            cb.SetTextMatrix(document.PageSize.GetRight(200), document.PageSize.GetTop(45));
            float len = bf.GetWidthPoint(text, 12);
            //Adds "12" in Page 1 of 12
            cb.AddTemplate(headerTemplate, document.PageSize.GetRight(200) + len, document.PageSize.GetTop(45));
        //Add paging to footer
            cb.SetFontAndSize(bf, 12);
            cb.SetTextMatrix(document.PageSize.GetRight(180), document.PageSize.GetBottom(30));
            float len = bf.GetWidthPoint(text, 12);
            cb.AddTemplate(footerTemplate, document.PageSize.GetRight(180) + len, document.PageSize.GetBottom(30));

        //Row 2
        PdfPCell pdfCell4 = new PdfPCell(new Phrase("Sub Header Description", baseFontNormal));

        //Row 3 
        PdfPCell pdfCell5 = new PdfPCell(new Phrase("Date:" + PrintTime.ToShortDateString(), baseFontBig));
        PdfPCell pdfCell6 = new PdfPCell();
        PdfPCell pdfCell7 = new PdfPCell(new Phrase("TIME:" + string.Format("{0:t}", DateTime.Now), baseFontBig));    

        //set the alignment of all three cells and set border to 0
        pdfCell1.HorizontalAlignment = Element.ALIGN_CENTER;
        pdfCell2.HorizontalAlignment = Element.ALIGN_CENTER;
        pdfCell3.HorizontalAlignment = Element.ALIGN_CENTER;
        pdfCell4.HorizontalAlignment = Element.ALIGN_CENTER;
        pdfCell5.HorizontalAlignment = Element.ALIGN_CENTER;
        pdfCell6.HorizontalAlignment = Element.ALIGN_CENTER;
        pdfCell7.HorizontalAlignment = Element.ALIGN_CENTER;    

        pdfCell2.VerticalAlignment = Element.ALIGN_BOTTOM;
        pdfCell3.VerticalAlignment = Element.ALIGN_MIDDLE;
        pdfCell4.VerticalAlignment = Element.ALIGN_TOP;
        pdfCell5.VerticalAlignment = Element.ALIGN_MIDDLE;
        pdfCell6.VerticalAlignment = Element.ALIGN_MIDDLE;
        pdfCell7.VerticalAlignment = Element.ALIGN_MIDDLE;    

        pdfCell4.Colspan = 3;  

        pdfCell1.Border = 0;
        pdfCell2.Border = 0;
        pdfCell3.Border = 0;
        pdfCell4.Border = 0;
        pdfCell5.Border = 0;
        pdfCell6.Border = 0;
        pdfCell7.Border = 0;    

        //add all three cells into PdfTable

        pdfTab.TotalWidth = document.PageSize.Width - 80f;
        pdfTab.WidthPercentage = 70;
        //pdfTab.HorizontalAlignment = Element.ALIGN_CENTER;    

        //call WriteSelectedRows of PdfTable. This writes rows from PdfWriter in PdfTable
        //first param is start row. -1 indicates there is no end row and all the rows to be included to write
        //Third and fourth param is x and y position to start writing
        pdfTab.WriteSelectedRows(0, -1, 40, document.PageSize.Height - 30, writer.DirectContent);
        //set pdfContent value

        //Move the pointer and draw line to separate header section from rest of page
        cb.MoveTo(40, document.PageSize.Height - 100);
        cb.LineTo(document.PageSize.Width - 40, document.PageSize.Height - 100);

        //Move the pointer and draw line to separate footer section from rest of page
        cb.MoveTo(40, document.PageSize.GetBottom(50) );
        cb.LineTo(document.PageSize.Width - 40, document.PageSize.GetBottom(50));

    public override void OnCloseDocument(PdfWriter writer, Document document)
        base.OnCloseDocument(writer, document);

        headerTemplate.SetFontAndSize(bf, 12);
        headerTemplate.SetTextMatrix(0, 0);
        headerTemplate.ShowText((writer.PageNumber - 1).ToString());

        footerTemplate.SetFontAndSize(bf, 12);
        footerTemplate.SetTextMatrix(0, 0);
        footerTemplate.ShowText((writer.PageNumber - 1).ToString());

I hope it helps!



Compile as 2.1 without android:installLocation="preferExternal".


Compile as 2.2 including android:installLocation="preferExternal".

This will still install on SDK version less than 8 (the XML tag is ignored).

Label axes on Seaborn Barplot

One can avoid the AttributeError brought about by set_axis_labels() method by using the matplotlib.pyplot.xlabel and matplotlib.pyplot.ylabel.

matplotlib.pyplot.xlabel sets the x-axis label while the matplotlib.pyplot.ylabel sets the y-axis label of the current axis.

Solution code:

import pandas as pd
import seaborn as sns
import matplotlib.pyplot as plt

fake = pd.DataFrame({'cat': ['red', 'green', 'blue'], 'val': [1, 2, 3]})
fig = sns.barplot(x = 'val', y = 'cat', data = fake, color = 'black')
plt.title("Colors vs Values") # You can comment this line out if you don't need title

Output figure:

enter image description here

How to convert the following json string to java object?

No need to go with GSON for this; Jackson can do either plain Maps/Lists:

ObjectMapper mapper = new ObjectMapper();
Map<String,Object> map = mapper.readValue(json, Map.class);

or more convenient JSON Tree:

JsonNode rootNode = mapper.readTree(json);

By the way, there is no reason why you could not actually create Java classes and do it (IMO) more conveniently:

public class Library {
  public String name;

  public List<Song> songs;
public class Song {
  @JsonProperty("Artist Name") public String artistName;
  @JsonProperty("Song Name") public String songName;

Library lib = mapper.readValue(jsonString, Library.class);

Gradient of n colors ranging from color 1 and color 2

Try the following:

color.gradient <- function(x, colors=c("red","yellow","green"), colsteps=100) {
  return( colorRampPalette(colors) (colsteps) [ findInterval(x, seq(min(x),max(x), length.out=colsteps)) ] )
x <- c((1:100)^2, (100:1)^2)
plot(x,col=color.gradient(x), pch=19,cex=2)

enter image description here

Chrome's remote debugging (USB debugging) not working for Samsung Galaxy S3 running android 4.3

My devices stopped working as Chrome de-activated the now depracated ADB plugin as it's built in dev-tools now.

I downloaded the SDK and followed the instructions at Chrome Developers. How ever I found the instructions served by Alphonso out not to be sufficient and I did it this way on Windows 8:

  1. Download Android SDK here ("SDK Tools Only" section) and unzip the content.
  2. Run SDK Manager.exe and install Android SDK platform tools
  3. Open up the Command prompt (simply by pressing the windows button and type in cmd.exe)
  4. Enter the path with ex: cd c:/downloads/sdk/platform-tools
  5. Open ADB by typing in adb.exe
  6. Run the following command by typing it and pressing enter: adb devices
  7. Check if you get the prompt on your device, if you still can't see your phone in Inspect Devices run the following commands one by one (excluding the ") "adb kill-server" "adb start-server" "adb devices"

I had major problems and managed to get it working with these steps. If you still have problems, google the guide Remote Debugging on Android with Chrome and check for the part about drivers. I had problems with my Samsung Galaxy Nexus that needed special drivers to be compatiable with ADB.


If you are using Windows 10 and couldn't find the link to download Android SDK; you may skip #1 and #2. All you need is activate "Android Debug Bridge". Go straight to #3 - #7 after download and execute "platform-tools"(

Table-level backup

BMC Recovery Manager (formerly known as SQLBacktrack) allows point-in-time recovery of individual objects in a database (aka tables). It is not cheap but does a fantastic job:,2832,19052_19429_70025639_147752,00.html,2832,19052_19429_67883151_147636,00.html

What is the purpose of the : (colon) GNU Bash builtin?

Self-documenting functions

You can also use : to embed documentation in a function.

Assume you have a library script, providing a variety of functions. You could either source the library (. and call the functions directly after that (lib_function1 arg1 arg2), or avoid cluttering your namespace and invoke the library with a function argument ( lib_function1 arg1 arg2).

Wouldn't it be nice if you could also type --help and get a list of available functions and their usage, without having to manually maintain the function list in the help text?


# all "public" functions must start with this prefix

# "public" library functions
lib_function1() {
    : This function does something complicated with two arguments.
    : Parameters:
    : '   arg1 - first argument ($1)'
    : '   arg2 - second argument'
    : Result:
    : "   it's complicated"

    # actual function code starts here

lib_function2() {
    : Function documentation

    # function code here

# help function
--help() {
    echo MyLib v0.0.1
    echo Usage: [function_name [args]]
    echo Available functions:
    declare -f | sed -n -e '/^'$LIB_PREFIX'/,/^}$/{/\(^'$LIB_PREFIX'\)\|\(^[ \t]*:\)/{
        s/^\('$LIB_PREFIX'.*\) ()/\n=== \1 ===/;s/^[ \t]*: \?['\''"]\?/    /;s/['\''"]\?;\?$//;p}}'

# main code
if [ "${BASH_SOURCE[0]}" = "${0}" ]; then
    # the script was executed instead of sourced
    # invoke requested function or display help
    if [ "$(type -t - "$1" 2>/dev/null)" = function ]; then

A few comments about the code:

  1. All "public" functions have the same prefix. Only these are meant to be invoked by the user, and to be listed in the help text.
  2. The self-documenting feature relies on the previous point, and uses declare -f to enumerate all available functions, then filters them through sed to only display functions with the appropriate prefix.
  3. It is a good idea to enclose the documentation in single quotes, to prevent undesired expansion and whitespace removal. You'll also need to be careful when using apostrophes/quotes in the text.
  4. You could write code to internalize the library prefix, i.e. the user only has to type function1 and it gets translated internally to lib_function1. This is an exercise left to the reader.
  5. The help function is named "--help". This is a convenient (i.e. lazy) approach that uses the library invoke mechanism to display the help itself, without having to code an extra check for $1. At the same time, it will clutter your namespace if you source the library. If you don't like that, you can either change the name to something like lib_help or actually check the args for --help in the main code and invoke the help function manually.

C# Change A Button's Background Color

Code for set background color, for SolidColor:

button.Background = new SolidColorBrush(Color.FromArgb(Avalue, rValue, gValue, bValue));

How can I make a .NET Windows Forms application that only runs in the System Tray?

As far as I'm aware you have to still write the application using a form, but have no controls on the form and never set it visible. Use the NotifyIcon (an MSDN sample of which can be found here) to write your application.

Remove a data connection from an Excel 2010 spreadsheet in compatibility mode

Select a cell in the cell range in which the data is imported, then Menu > Data > Properties > uncheck save query definition.

Properties will be greyed out unless a cell in the data import range is selected.

You can find out the range in which the data isimported by:

Menu > Data > Connections > (select connection) > Click here to see where the selected connections are used.

Example: Communication between Activity and Service using Messaging

Great tutorial, fantastic presentation. Neat, simple, short and very explanatory. Although, notification.setLatestEventInfo(this, getText(R.string.service_label), text, contentIntent); method is no more. As trante stated here, good approach would be:

private static final int NOTIFICATION_ID = 45349;

private void showNotification() {
    NotificationCompat.Builder builder =
            new NotificationCompat.Builder(this)
                    .setContentTitle("My Notification Title")
                    .setContentText("Something interesting happened");

    Intent targetIntent = new Intent(this, MainActivity.class);
    PendingIntent contentIntent = PendingIntent.getActivity(this, 0, targetIntent, PendingIntent.FLAG_UPDATE_CURRENT);
    _nManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

public void onDestroy() {
    if (_timer != null) {_timer.cancel();}
    _nManager.cancel(NOTIFICATION_ID); // Cancel the persistent notification.
    Log.i("PlaybackService", "Service Stopped.");
    _isRunning = false;

Checked myself, everything works like a charm (activity and service names may differ from original).

Datagrid binding in WPF

PLEASE do not use object as a class name:

public class MyObject //better to choose an appropriate name
    string id;
    DateTime date;
    public string ID
       get { return id; }
       set { id = value; }
    public DateTime Date
       get { return date; }
       set { date = value; }

You should implement INotifyPropertyChanged for this class and of course call it on the Property setter. Otherwise changes are not reflected in your ui.

Your Viewmodel class/ dialogbox class should have a Property of your MyObject list. ObservableCollection<MyObject> is the way to go:

public ObservableCollection<MyObject> MyList

In your xaml you should set the Itemssource to your collection of MyObject. (the Datacontext have to be your dialogbox class!)

<DataGrid ItemsSource="{Binding Source=MyList}"  AutoGenerateColumns="False">
     <DataGridTextColumn Header="ID" Binding="{Binding ID}"/>
     <DataGridTextColumn Header="Date" Binding="{Binding Date}"/>

What is the curl error 52 "empty reply from server"?

you can try this curl -sS "" by putting your URL into "" that worked for me I don't know the exact reason but I suppose that putting the url into "" completes the request to the server or just completes the header request.

How to check if an array element exists?

You can also use array_keys for number of occurrences

$i=count(array_keys($array, 6));
 echo "Element exists in Array";

check if command was successful in a batch file

Most commands/programs return a 0 on success and some other value, called errorlevel, to signal an error.

You can check for this in you batch for example by:

if %ERRORLEVEL% == 0 goto :next
echo "Errors encountered during execution.  Exited with status: %errorlevel%"
goto :endofscript

echo "Doing the next thing"

echo "Script complete"

Error:Execution failed for task ':ProjectName:mergeDebugResources'. > Crunching Cruncher *some file* failed, see logs

As stated here this can happen when using the Gradle Tools v1.1.0. After updating to v1.1.3, this has not happened anymore.

SSLHandshakeException: No subject alternative names present

Unlike some browsers, Java follows the HTTPS specification strictly when it comes to the server identity verification (RFC 2818, Section 3.1) and IP addresses.

When using a host name, it's possible to fall back to the Common Name in the Subject DN of the server certificate, instead of using the Subject Alternative Name.

When using an IP address, there must be a Subject Alternative Name entry (of type IP address, not DNS name) in the certificate.

You'll find more details about the specification and how to generate such a certificate in this answer.

How do I prevent DIV tag starting a new line?

A better way to do a break line is using span with CSS style parameter white-space: nowrap;

span.nobreak {
  white-space: nowrap;

span.nobreak {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;

Example directly in your HTML

<span style='overflow:hidden; white-space: nowrap;'> YOUR EXTENSIVE TEXT THAT YOU CAN´T BREAK LINE ....</span>

How to determine whether code is running in DEBUG / RELEASE build?

In xcode 7, there is a field under Apple LLVM 7.0 - preprocessing, which called "Preprocessors Macros Not Used In Precompiled..." I put DEBUG in front of Debug and it works for me by using below code:

#ifdef DEBUG
    NSString* const kURL = @"";
    NSString* const kURL = @"";

ERROR:'keytool' is not recognized as an internal or external command, operable program or batch file

This worked for me !! :

Go to this path or where ever you have your keytool.exe file

C:\Program Files\Java\jre7\bin

Hold shift and right click -> then press Open command window here

terminal will pop up, paste this in:

keytool -list -v -keystore "C:\Users\"Your-User-Name(no quotes)"\.android\debug.keystore" -alias androiddebugkey -storepass android -keypass android

gives you both MD5 and SHA1

disable Bootstrap's Collapse open/close animation

For Bootstrap 3 and 4 it's

.collapsing {
    -webkit-transition: none;
    transition: none;
    display: none;

How to exclude subdirectories in the destination while using /mir /xd switch in robocopy

The way you can exclude a destination directory while using the /mir is by making sure the destination directory also exists on the source. I went into my source drive and created blank directories with the same name as on the destination, and then added that directory name to the /xd. It successfully mirrored everything while excluding the directory on the source, thereby leaving the directory on the destination intact.

How to set default value to all keys of a dict object in python?

Use defaultdict

from collections import defaultdict
a = {} 
a = defaultdict(lambda:0,a)
a["anything"] # => 0

This is very useful for case like this,where default values for every key is set as 0:

results ={ 'pre-access' : {'count': 4, 'pass_count': 2},'no-access' : {'count': 55, 'pass_count': 19}
for k,v in results.iteritems():
  a['count'] += v['count']
  a['pass_count'] += v['pass_count']

What is the best way to manage a user's session in React?

There is a React module called react-client-session that makes storing client side session data very easy. The git repo is here.

This is implemented in a similar way as the closure approach in my other answer, however it also supports persistence using 3 different persistence stores. The default store is memory(not persistent).

  1. Cookie
  2. localStorage
  3. sessionStorage

After installing, just set the desired store type where you mount the root component ...

import ReactSession from 'react-client-session';


... and set/get key value pairs from anywhere in your app:

import ReactSession from 'react-client-session';

ReactSession.set("username", "Bob");
ReactSession.get("username");  // Returns "Bob"

How do I find out what keystore my JVM is using?

You can find it in your "Home" directory:

On Windows 7:


On Linux (Ubuntu):


Convert time span value to format "hh:mm Am/Pm" using C#

You can do this by adding your timespan to the date.

TimeSpan timespan = new TimeSpan(03,00,00);
DateTime time = DateTime.Today.Add(timespan);
string displayTime = time.ToString("hh:mm tt"); // It will give "03:00 AM"

xcopy file, rename, suppress "Does xxx specify a file name..." message

The right thing to do if you wanna copy just file and change it's name at destination is :

xcopy /f /y "bin\development\example.exe" "TestConnectionExternal\bin\Debug\NewName.exe*"

And it's Gonna work fine

Get OS-level system information

For windows I went this way. os = ( ManagementFactory.getOperatingSystemMXBean();

    long physicalMemorySize = os.getTotalPhysicalMemorySize();
    long freePhysicalMemory = os.getFreePhysicalMemorySize();
    long freeSwapSize = os.getFreeSwapSpaceSize();
    long commitedVirtualMemorySize = os.getCommittedVirtualMemorySize();

Here is the link with details.

How do you delete a column by name in data.table?

Here is a way when you want to set a # of columns to NULL given their column names a function for your usage :)

deleteColsFromDataTable <- function (train, toDeleteColNames) {

       for (myNm in toDeleteColNames)

       train <- train [,(myNm):=NULL]

       return (train)

On linux SUSE or RedHat, how do I load Python 2.7

Great thing about linux, you're still able to download the source and on most systems have all of the tools to compile the version yourself.

In order to get a python cli from xterm just by typing python, the python bin directory must be in your system path variable (Red Hat example, Suse example)

How do I create a MongoDB dump of my database?

take mongodb backup for particular db and delete 7 days old backup using bin sh command :-


TIMESTAMP=`date +%F-%H%M`
mkdir -p $BACKUPS_DIR
mv dump $BACKUP_NAME
find /home/mongodbbackups/backups/test/ -mindepth 1 -mtime +7 -delete

How to write a UTF-8 file with Java?

Instead of using FileWriter, create a FileOutputStream. You can then wrap this in an OutputStreamWriter, which allows you to pass an encoding in the constructor. Then you can write your data to that inside a try-with-resources Statement:

try (OutputStreamWriter writer =
             new OutputStreamWriter(new FileOutputStream(PROPERTIES_FILE), StandardCharsets.UTF_8))
    // do stuff

How to remove decimal part from a number in C#

Because the numbers after point is only zero, the best solution is to use the Math.Round(MyNumber)

How do I programmatically click a link with javascript?

Client Side JS function to automatically click a link when...

Here is an example where you check the value of a hidden form input, which holds an error passed down from the server.. your client side JS then checks the value of it and populates an error in another location that you this case a pop-up login modal.

var signUperror = document.getElementById('handleError')

if (signUperror) {
  if(signUperror.innerHTML != ""){
  var clicker = function(){

Failed to find target with hash string 'android-25'

It seems like that it is only me who are so clumsy, because i have yet to found a solution that my case required.

I am developing a multi-modular project, thus base android module configuration is extracted in single gradle script. All the concrete versions of sdks/libs are also extracted in a script.

A script containing versions looked like this:


ext.androidVersions = [
    compile_sdk_version     : '27',
    min_sdk_version         : '19',
    target_sdk_version      : '27',
    build_tool_version      : '27.0.3',
    application_id          : 'com.test.test',


Not accustomed to groovy syntax my eye has not spotted that the values for compile, min and target sdks were not integers but STRINGS! Therefore a compiler rightfully complained about not being able to find an sdk a version of which would match HASH STRING '27'.

So the solution would be to make sdk's versions integers: ...

ext.androidVersions = [
    compile_sdk_version     : 27,
    min_sdk_version         : 19,
    target_sdk_version      : 27,
    build_tool_version      : '27.0.3',
    application_id          : 'com.test.test',


Fastest way to check if a value exists in a list

Code to check whether two elements exist in array whose product equals k:

n = len(arr1)
for i in arr1:
    if k%i==0:

What's the source of Error: getaddrinfo EAI_AGAIN?

EAI_AGAIN is a DNS lookup timed out error, means it is a network connectivity error or proxy related error.

My main question is what does dns.js do?

  • The dns.js is there for node to get ip address of the domain(in brief).

Some more info:

How to get cumulative sum

The latest version of SQL Server (2012) permits the following.

FROM tablehh


FROM tablehh

This is even faster. Partitioned version completes in 34 seconds over 5 million rows for me.

Thanks to Peso, who commented on the SQL Team thread referred to in another answer.

Twitter Bootstrap Responsive Background-Image inside Div

Try this (apply to a class you image is in (not img itself), e.g.

.myimage {
  background: transparent url("yourimage.png") no-repeat top center fixed;
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: 100%;
  height: 500px;

Hive Alter table change Column Name

In the comments @libjack mentioned a point which is really important. I would like to illustrate more into it. First, we can check what are the columns of our table by describe <table_name>; command. enter image description here

there is a double-column called _c1 and such columns are created by the hive itself when we moving data from one table to another. To address these columns we need to write it inside backticks


Finally, the ALTER command will be,

ALTER TABLE <table_namr> CHANGE `<system_genarated_column_name>` <new_column_name> <data_type>;

Cloning specific branch

you can use this command for particular branch clone :

git clone <url of repo> -b <branch name to be cloned>

Eg: git clone -b master

Warning: mysql_connect(): [2002] No such file or directory (trying to connect via unix:///tmp/mysql.sock) in

For some reason mysql on OS X gets the locations of the required socket file a bit wrong, but thankfully the solution is as simple as setting up a symbolic link.

You may have a socket (appearing as a zero length file) as /tmp/mysql.sock or /var/mysql/mysql.sock, but one or more apps is looking in the other location for it. Find out with this command:

ls -l /tmp/mysql.sock /var/mysql/mysql.sock

Rather than move the socket, edit config files, and have to remember to keep edited files local and away from servers where the paths are correct, simply create a symbolic link so your Mac finds the required socket, even when it's looking in the wrong place!

If you have /tmp/mysql.sock but no /var/mysql/mysql.sock then...

cd /var 
sudo mkdir mysql
sudo chmod 755 mysql
cd mysql
sudo ln -s /tmp/mysql.sock mysql.sock

If you have /var/mysql/mysql.sock but no /tmp/mysql.sock then...

cd /tmp
ln -s /var/mysql/mysql.sock mysql.sock

You will need permissions to create the directory and link, so just prefix the commands above with sudo if necessary.

Regular expression include and exclude special characters


This would do the matching, if you only want to allow that just wrap it in ^$ or any other delimiters that you see appropriate, if you do this no specific disallow logic is needed.

How can I find the length of a number?

Ok, so many answers, but this is a pure math one, just for the fun or for remembering that Math is Important:

var len = Math.ceil(Math.log(num + 1) / Math.LN10);

This actually gives the "length" of the number even if it's in exponential form. num is supposed to be a non negative integer here: if it's negative, take its absolute value and adjust the sign afterwards.

Update for ES2015

Now that Math.log10 is a thing, you can simply write

const len = Math.ceil(Math.log10(num + 1));

Application Crashes With "Internal Error In The .NET Runtime"

A bug in the concurrent implementation of the Garbage Collection on x64 .Net 4 can cause this as stated in the following microsoft KB entry:

ExecutionEngineException occurs during Garbage Collection

You should first make a deep minidump exploration to be sure that the problem occured during a Garbage collection.

The minidump location can usually be found in a Windows Error Reporting entry in the event log following the crash entry. Then, have fun with WinDbg !

The latest documentation on the use of the <gcConcurrent/> configuration element, to disable concurrent or (in .NET 4 and later) background garbage collection, can be found here.

How to Call VBA Function from Excel Cells?

The issue you have encountered is that UDFs cannot modify the Excel environment, they can only return a value to the calling cell.

There are several alternatives

  1. For the sample given you don't actually need VBA. This formula will work

  2. Use a rather messy work around: See this answer

  3. You can use ExecuteExcel4Macro or OLEDB

Find all special characters in a column in SQL Server 2008

Select * from TableName Where ColumnName LIKE '%[^A-Za-z0-9, ]%'

This will give you all the row which contains any special character.

pandas convert some columns into rows

From v0.20, melt is a first order function, you can now use

df.melt(id_vars=["location", "name"], 

  location    name        Date  Value
0        A  "test"    Jan-2010     12
1        B   "foo"    Jan-2010     18
2        A  "test"    Feb-2010     20
3        B   "foo"    Feb-2010     20
4        A  "test"  March-2010     30
5        B   "foo"  March-2010     25


You can use pd.melt to get most of the way there, and then sort:

>>> df
  location  name  Jan-2010  Feb-2010  March-2010
0        A  test        12        20          30
1        B   foo        18        20          25
>>> df2 = pd.melt(df, id_vars=["location", "name"], 
                  var_name="Date", value_name="Value")
>>> df2
  location  name        Date  Value
0        A  test    Jan-2010     12
1        B   foo    Jan-2010     18
2        A  test    Feb-2010     20
3        B   foo    Feb-2010     20
4        A  test  March-2010     30
5        B   foo  March-2010     25
>>> df2 = df2.sort(["location", "name"])
>>> df2
  location  name        Date  Value
0        A  test    Jan-2010     12
2        A  test    Feb-2010     20
4        A  test  March-2010     30
1        B   foo    Jan-2010     18
3        B   foo    Feb-2010     20
5        B   foo  March-2010     25

(Might want to throw in a .reset_index(drop=True), just to keep the output clean.)

Note: pd.DataFrame.sort has been deprecated in favour of pd.DataFrame.sort_values.

HTML <select> selected option background-color CSS style


SELECT OPTION:checked { background-color: red; }

Boolean Field in Oracle

In our databases we use an enum that ensures we pass it either TRUE or FALSE. If you do it either of the first two ways it is too easy to either start adding new meaning to the integer without going through a proper design, or ending up with that char field having Y, y, N, n, T, t, F, f values and having to remember which section of code uses which table and which version of true it is using.

How can I get browser to prompt to save password?

I have been struggling with this myself, and I finally was able to track down the issue and what was causing it to fail.

It all stemmed from the fact that my login form was being dynamically injected into the page (using backbone.js). As soon as I embed my login form directly into my index.html file, everything worked like a charm.

I think this is because the browser has to be aware that there is an existing login form, but since mine was being dynamically injected into the page, it didn't know that a "real" login form ever existed.

What version of MongoDB is installed on Ubuntu

In the terminal just write : $ mongod --version

Rename a table in MySQL


tb1 - current table name. tb2 - the name you want your table to be called.

Shortcut to Apply a Formula to an Entire Column in Excel

If the formula already exists in a cell you can fill it down as follows:

  • Select the cell containing the formula and press CTRL+SHIFT+DOWN to select the rest of the column (CTRL+SHIFT+END to select up to the last row where there is data)
  • Fill down by pressing CTRL+D
  • Use CTRL+UP to return up

On Mac, use CMD instead of CTRL.

An alternative if the formula is in the first cell of a column:

  • Select the entire column by clicking the column header or selecting any cell in the column and pressing CTRL+SPACE
  • Fill down by pressing CTRL+D

How Do I Upload Eclipse Projects to GitHub?

Many of these answers mention how to share the project on Git, which is easy, you just share the code on git, but one thing to take note of is that there is no apparent "project file" that the end user can double click on. Instead you have to use Import->General->Existing project and select the whole folder

Converting EditText to int? (Android)

Use Integer.parseInt, and make sure you catch the NumberFormatException that it throws if the input is not an integer.

How to use the DropDownList's SelectedIndexChanged event

You should add AutoPostBack="true" to DropDownList1

                <asp:DropDownList ID="ddmanu" runat="server" AutoPostBack="true"
                    DataTextField="manufacturer" DataValueField="manufacturer" 

Reference member variables as class members

Is there a name to describe this idiom?

In UML it is called aggregation. It differs from composition in that the member object is not owned by the referring class. In C++ you can implement aggregation in two different ways, through references or pointers.

I am assuming it is to prevent the possibly large overhead of copying a big complex object?

No, that would be a really bad reason to use this. The main reason for aggregation is that the contained object is not owned by the containing object and thus their lifetimes are not bound. In particular the referenced object lifetime must outlive the referring one. It might have been created much earlier and might live beyond the end of the lifetime of the container. Besides that, the state of the referenced object is not controlled by the class, but can change externally. If the reference is not const, then the class can change the state of an object that lives outside of it.

Is this generally good practice? Are there any pitfalls to this approach?

It is a design tool. In some cases it will be a good idea, in some it won't. The most common pitfall is that the lifetime of the object holding the reference must never exceed the lifetime of the referenced object. If the enclosing object uses the reference after the referenced object was destroyed, you will have undefined behavior. In general it is better to prefer composition to aggregation, but if you need it, it is as good a tool as any other.

How to include libraries in Visual Studio 2012?

Typically you need to do 5 things to include a library in your project:

1) Add #include statements necessary files with declarations/interfaces, e.g.:

#include "library.h"

2) Add an include directory for the compiler to look into

-> Configuration Properties/VC++ Directories/Include Directories (click and edit, add a new entry)

3) Add a library directory for *.lib files:

-> project(on top bar)/properties/Configuration Properties/VC++ Directories/Library Directories (click and edit, add a new entry)

4) Link the lib's *.lib files

-> Configuration Properties/Linker/Input/Additional Dependencies (e.g.: library.lib;

5) Place *.dll files either:

-> in the directory you'll be opening your final executable from or into Windows/system32

Is it possible to pass parameters programmatically in a Microsoft Access update query?

Plenty of responses already, but you can use this:

Sub runQry(qDefName)
    Dim db As DAO.Database, qd As QueryDef, par As Parameter

    Set db = CurrentDb
    Set qd = db.QueryDefs(qDefName)

    On Error Resume Next
    For Each par In qd.Parameters
        par.Value = Eval(par.Name)          'try evaluating param
        If Err.Number <> 0 Then             'failed ?
            par.Value = InputBox(par.Name)  'ask for value
        End If
    Next par
    On Error GoTo 0

    qd.Execute dbFailOnError
End Sub

Sub runQry_test()
    runQry "test"  'qryDef name
End Sub

Where is Developer Command Prompt for VS2013?

Works with VS 2017
I did installed Visual Studio Command Prompt (devCmd) extension tool.
You can download it here:

Double click on the file, make sure IDE is closed during installation.
Open visual studio and Run Developer Command Prompt from VS2017

enter image description here

pandas groupby sort within groups

You can do it in one line -

df.groupby(['job']).apply(lambda x: x.sort_values(['count'], ascending=False).head(3)
.drop('job', axis=1))

what apply() does is that it takes each group of groupby and assigns it to the x in lambda function.


Q&A Style

Well, after researching and fighting with the problem for hours, I found out that there are two ways to accomplish this, depending on the structure of your table and if you have foreign keys restrictions activated to maintain integrity. I'd like to share this in a clean format to save some time to the people that may be in my situation.

Option 1: You can afford deleting the row

In other words, you don't have foreign key, or if you have them, your SQLite engine is configured so that there no are integrity exceptions. The way to go is INSERT OR REPLACE. If you are trying to insert/update a player whose ID already exists, the SQLite engine will delete that row and insert the data you are providing. Now the question comes: what to do to keep the old ID associated?

Let's say we want to UPSERT with the data user_name='steven' and age=32.

Look at this code:

INSERT INTO players (id, name, age)

    coalesce((select id from players where user_name='steven'),
             (select max(id) from drawings) + 1),

The trick is in coalesce. It returns the id of the user 'steven' if any, and otherwise, it returns a new fresh id.

Option 2: You cannot afford deleting the row

After monkeying around with the previous solution, I realized that in my case that could end up destroying data, since this ID works as a foreign key for other table. Besides, I created the table with the clause ON DELETE CASCADE, which would mean that it'd delete data silently. Dangerous.

So, I first thought of a IF clause, but SQLite only has CASE. And this CASE can't be used (or at least I did not manage it) to perform one UPDATE query if EXISTS(select id from players where user_name='steven'), and INSERT if it didn't. No go.

And then, finally I used the brute force, with success. The logic is, for each UPSERT that you want to perform, first execute a INSERT OR IGNORE to make sure there is a row with our user, and then execute an UPDATE query with exactly the same data you tried to insert.

Same data as before: user_name='steven' and age=32.

-- make sure it exists
INSERT OR IGNORE INTO players (user_name, age) VALUES ('steven', 32); 

-- make sure it has the right data
UPDATE players SET user_name='steven', age=32 WHERE user_name='steven'; 

And that's all!


As Andy has commented, trying to insert first and then update may lead to firing triggers more often than expected. This is not in my opinion a data safety issue, but it is true that firing unnecessary events makes little sense. Therefore, a improved solution would be:

-- Try to update any existing row
UPDATE players SET age=32 WHERE user_name='steven';

-- Make sure it exists
INSERT OR IGNORE INTO players (user_name, age) VALUES ('steven', 32); 

jQuery add text to span within a div

You can use append or prepend

The .append() method inserts the specified content as the last child of each element in the jQuery collection (To insert it as the first child, use .prepend()).

$("#tagscloud span").append(second);
$("#tagscloud span").append(third);
$("#tagscloud span").prepend(first);

Modifying list while iterating

Try this. It avoids mutating a thing you're iterating across, which is generally a code smell.

for i in xrange(0, 100, 3):
    print i

See xrange.

Error: " 'dict' object has no attribute 'iteritems' "

In Python2, dictionary.iteritems() is more efficient than dictionary.items() so in Python3, the functionality of dictionary.iteritems() has been migrated to dictionary.items() and iteritems() is removed. So you are getting this error.

Use dict.items() in Python3 which is same as dict.iteritems() of Python2.

How to echo or print an array in PHP?

This will do

foreach($results['data'] as $result) {
    echo $result['type'], '<br>';

Installing Apache Maven Plugin for Eclipse

  1. In Eclipse Select Help -> Marketplace

  2. Enter "Maven" in Find box and click on Go button

  3. Click on "Install" button for Maven Integration for Eclipse (Juno and newer)

With this, maven should get install without any problem.

Is there a limit on number of tcp/ip connections between machines on linux?

When looking for the max performance you run into a lot of issue and potential bottlenecks. Running a simple hello world test is not necessarily going to find them all.

Possible limitations include:

  • Kernel socket limitations: look in /proc/sys/net for lots of kernel tuning..
  • process limits: check out ulimit as others have stated here
  • as your application grows in complexity, it may not have enough CPU power to keep up with the number of connections coming in. Use top to see if your CPU is maxed
  • number of threads? I'm not experienced with threading, but this may come into play in conjunction with the previous items.

CodeIgniter: How to use WHERE clause and OR clause

$where = "name='Joe' AND status='boss' OR status='active'";


Though I am 3/4 of a month late, you still execute the following after your where clauses are defined... $this->db->get("tbl_name");

Redirect to Action by parameter mvc

Try this,

return RedirectToAction("ActionEventName", "Controller", new { ID = model.ID, SiteID = model.SiteID });

Here i mention you are pass multiple values or model also. That's why here i mention that.

How to define an optional field in protobuf 3

In proto3, all fields are "optional" (in that it is not an error if the sender fails to set them). But, fields are no longer "nullable", in that there's no way to tell the difference between a field being explicitly set to its default value vs. not having been set at all.

If you need a "null" state (and there is no out-of-range value that you can use for this) then you will instead need to encode this as a separate field. For instance, you could do:

message Foo {
  bool has_baz = 1;  // always set this to "true" when using baz
  int32 baz = 2;

Alternatively, you could use oneof:

message Foo {
  oneof baz {
    bool baz_null = 1;  // always set this to "true" when null
    int32 baz_value = 2;

The oneof version is more explicit and more efficient on the wire but requires understanding how oneof values work.

Finally, another perfectly reasonable option is to stick with proto2. Proto2 is not deprecated, and in fact many projects (including inside Google) very much depend on proto2 features which are removed in proto3, hence they will likely never switch. So, it's safe to keep using it for the foreseeable future.

What is the purpose of a question mark after a type (for example: int? myVariable)?

practical usage:

public string someFunctionThatMayBeCalledWithNullAndReturnsString(int? value)
  if (value == null)
    return "bad value";

  return someFunctionThatHandlesIntAndReturnsString(value);

How do I access an access array item by index in handlebars?

If you want to use dynamic variables

This won't work:

{{#each obj[key]}}

You need to do:

{{#each (lookup obj key)}}

see handlebars lookup helper and handlebars subexpressions.

get current date and time in groovy?

Date has the time as well, just add HH:mm:ss to the date format:

import java.text.SimpleDateFormat
def date = new Date()
def sdf = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss")
println sdf.format(date)

In case you are using JRE 8 you can use LoaclDateTime:

import java.time.*

LocalDateTime t =;
return t as String

How to run or debug php on Visual Studio Code (VSCode)

If you don't want to install xDebug or other extensions and just want to run a PHP file without debugging, you can accomplish this using build tasks.

Using Build Tasks

First open the command palette (Ctrl+Shift+P in Windows, ?+Shift+P in Mac), and select "Tasks:Open User Tasks". Now copy my configuration below into your tasks.json file. This creates user-level tasks which can be used any time and in any workspace.

    "version": "2.0.0",
    "tasks": [
            "label": "Start Server",
            "type": "shell",
            "command": "php -S localhost:8080 -t ${fileDirname}",
            "isBackground": true,
            "group": "build",
            "problemMatcher": []
            "label": "Run In Browser",
            "type": "shell",
            "command": "open http://localhost:8080/${fileBasename}",
            "windows": {
                "command": "explorer 'http://localhost:8080/${fileBasename}'"
            "group": "build",
            "problemMatcher": []
            "label": "Run In Terminal",
            "type": "shell",
            "command": "php ${file}",
            "group": "none",
            "problemMatcher": []

If you want to run your php file in the terminal, open the command palette and select "Tasks: Run Task" followed by "Run In Terminal".

If you want to run your code on a webserver which serves a response to a web browser, open the command palette and select "Tasks: Run Task" followed by "Start Server" to run PHP's built-in server, then "Run In Browser" to run the currently open file from your browser.

Note that if you already have a webserver running, you can remove the Start Server task and update the localhost:8080 part to point to whatever URL you are using.

Using PHP Debug

Note: This section was in my original answer. I originally thought that it works without PHP Debug but it looks like PHP Debug actually exposes the php type in the launch configuration. There is no reason to use it over the build task method described above. I'm keeping it here in case it is useful.

Copy the following configuration into your user settings:

    "launch": {
        "version": "0.2.0",
        "configurations": [
            "type": "php",
            "request": "launch",
            "name": "Run using PHP executable",
            "program": "${file}",
            "runtimeExecutable": "/usr/bin/php"
    // all your other user settings...

This creates a global launch configuration that you can use on any PHP file. Note the runtimeExecutable option. You will need to update this with the path to the PHP executable on your machine. After you copy the configuration above, whenever you have a PHP file open, you can press the F5 key to run the PHP code and have the output displayed in the vscode terminal.

Writing outputs to log file and console

I wanted to display logs on stdout and log file along with the timestamp. None of the above answers worked for me. I made use of process substitution and exec command and came up with the following code. Sample logs:

2017-06-21 11:16:41+05:30 Fetching information about files in the directory...

Add following lines at the top of your script:

exec > >(while read -r line; do printf '%s %s\n' "$(date --rfc-3339=seconds)" "$line" | tee -a $LOG_FILE; done)
exec 2> >(while read -r line; do printf '%s %s\n' "$(date --rfc-3339=seconds)" "$line" | tee -a $LOG_FILE; done >&2)

Hope this helps somebody!

Django Model() vs Model.objects.create()

The differences between Model() and Model.objects.create() are the following:

  1. INSERT vs UPDATE does either INSERT or UPDATE of an object in a DB, while Model.objects.create() does only INSERT. does

    • UPDATE If the object’s primary key attribute is set to a value that evaluates to True

    • INSERT If the object’s primary key attribute is not set or if the UPDATE didn’t update anything (e.g. if primary key is set to a value that doesn’t exist in the database).

  1. Existing primary key

    If primary key attribute is set to a value and such primary key already exists, then performs UPDATE, but Model.objects.create() raises IntegrityError.

    Consider the following

    class Subject(models.Model):
       subject_id = models.PositiveIntegerField(primary_key=True, db_column='subject_id')
       name = models.CharField(max_length=255)
       max_marks = models.PositiveIntegerField()
    1. Insert/Update to db with

      physics = Subject(subject_id=1, name='Physics', max_marks=100)
      math = Subject(subject_id=1, name='Math', max_marks=50)  # Case of update


      <QuerySet [{'subject_id': 1, 'name': 'Math', 'max_marks': 50}]>
    2. Insert to db with Model.objects.create()

      Subject.objects.create(subject_id=1, name='Chemistry', max_marks=100)
      IntegrityError: UNIQUE constraint failed: m****t.subject_id

    Explanation: In the example, does an UPDATE (changes name from Physics to Math, and max_marks from 100 to 50), because subject_id is a primary key and subject_id=1 already exists in the DB. But Subject.objects.create() raises IntegrityError, because, again the primary key subject_id with the value 1 already exists.

  1. Forced insert can be made to behave as Model.objects.create() by using force_insert=True parameter:

  1. Return value return None where Model.objects.create() return model instance i.e. package_name.models.Model

Conclusion: Model.objects.create() does model initialization and performs save() with force_insert=True.

Excerpt from the source code of Model.objects.create()

def create(self, **kwargs):
    Create a new object with the given kwargs, saving it to the database
    and returning the created object.
    obj = self.model(**kwargs)
    self._for_write = True, using=self.db)
    return obj

For more details follow the links:



How do I install cURL on Windows?

I have tried everything - but nothing helped. After searching for several hours I found this information:

Apache 2.4.18 for some reason does not load php 7.2 curl. I updated my Apache to 2.4.29 and curl loaded instantly,149346,149348

What should I say: I updated Apache and curl was running like charm

How to use setprecision in C++

#include <iostream>
#include <iomanip>
using namespace std;

You can enter the line using namespace std; for your convenience. Otherwise, you'll have to explicitly add std:: every time you wish to use cout, fixed, showpoint, setprecision(2) and endl

int main()
    double num1 = 3.12345678;
    cout << fixed << showpoint;
    cout << setprecision(2);
    cout << num1 << endl;
return 0;

How to unbind a listener that is calling event.preventDefault() (using jQuery)?

You can restore the default action (if it is a HREF follow) by doing this:

window.location = $(this).attr('href');

Copy struct to struct in C

Also a good example.....

struct point{int x,y;};
typedef struct point point_t;
typedef struct
    struct point ne,se,sw,nw;
rect_t temp;

int main()
    return 0;

void RotateRect(rect_t *givenRect)
    point_t temp_point;
    /*Copy struct data from struct to struct within a struct*/
    temp_point = givenRect->sw;
    givenRect->sw = givenRect->se;
    givenRect->se = givenRect->ne;
    givenRect->ne = givenRect->nw;
    givenRect->nw = temp_point;

Loop through all elements in XML using NodeList

Here is another way to loop through XML elements using JDOM.

        List<Element> nodeNodes = inputNode.getChildren();
        if (nodeNodes != null) {
            for (Element nodeNode : nodeNodes) {
                List<Element> elements = nodeNode.getChildren(elementName);
                if (elements != null) {

MySQL config file location - redhat linux server

From the header of '/etc/mysql/my.cnf':

MariaDB programs look for option files in a set of
locations which depend on the deployment platform.
[...] For information about these locations, do:
'my_print_defaults --help' and see what is printed under
"Default options are read from the following files in the given order:"
More information at:

How do I split a multi-line string into multiple lines?


Will give you a list with each item, the splitlines() method is designed to split each line into a list element.

Oracle: If Table Exists

I prefer following economic solution


How to change a package name in Eclipse?

com.myCompany.executabe is the path of executabe package. Here com,myCompany,executable are three different package. You have to manually rename individual package name you want to change.

Error: Expression must have integral or unscoped enum type

Your variable size is declared as: float size;

You can't use a floating point variable as the size of an array - it needs to be an integer value.

You could cast it to convert to an integer:

float *temp = new float[(int)size];

Your other problem is likely because you're writing outside of the bounds of the array:

   float *temp = new float[size];

    //Getting input from the user
    for (int x = 1; x <= size; x++){
        cout << "Enter temperature " << x << ": ";

        // cin >> temp[x];
        // This should be:
        cin >> temp[x - 1];

Arrays are zero based in C++, so this is going to write beyond the end and never write the first element in your original code.

javascript filter array multiple conditions

You can do like this

var filter = {_x000D_
  address: 'England',_x000D_
  name: 'Mark'_x000D_
var users = [{_x000D_
    name: 'John',_x000D_
    email: '[email protected]',_x000D_
    age: 25,_x000D_
    address: 'USA'_x000D_
    name: 'Tom',_x000D_
    email: '[email protected]',_x000D_
    age: 35,_x000D_
    address: 'England'_x000D_
    name: 'Mark',_x000D_
    email: '[email protected]',_x000D_
    age: 28,_x000D_
    address: 'England'_x000D_
users= users.filter(function(item) {_x000D_
  for (var key in filter) {_x000D_
    if (item[key] === undefined || item[key] != filter[key])_x000D_
      return false;_x000D_
  return true;_x000D_

Upload artifacts to Nexus, without Maven

@Adam Vandenberg For Java code to POST to Nexus.

public class NexusRepository implements RepoTargetFactory {

    String DIRECTORY_KEY= "";
    String ASSET_KEY= "raw.asset1";
    String FILENAME_KEY= "raw.asset1.filename";

    String repoUrl;
    String userName;
    String password;

    public void setRepoConfigurations(String repoUrl, String userName, String password) {
        this.repoUrl = repoUrl;
        this.userName = userName;
        this.password = password;

    public String pushToRepository() {
        HttpClient httpclient = HttpClientBuilder.create().build();
        HttpPost postRequest = new HttpPost(repoUrl) ;
        String auth = userName + ":" + password;
        byte[] encodedAuth = Base64.encodeBase64(
        String authHeader = "Basic " + new String(encodedAuth);
        postRequest.setHeader(HttpHeaders.AUTHORIZATION, authHeader);
            byte[] packageBytes = "Hello. This is my file content".getBytes();
            MultipartEntityBuilder multipartEntityBuilder = MultipartEntityBuilder.create();
            InputStream packageStream = new ByteArrayInputStream(packageBytes);
            InputStreamBody inputStreamBody = new InputStreamBody(packageStream, ContentType.APPLICATION_OCTET_STREAM);
            multipartEntityBuilder.addPart(DIRECTORY_KEY, new StringBody("DIRECTORY"));
            multipartEntityBuilder.addPart(FILENAME_KEY, new StringBody("MyFile.txt"));
            multipartEntityBuilder.addPart(ASSET_KEY, inputStreamBody);
            HttpEntity entity =;
            postRequest.setEntity(entity); ;

            HttpResponse response = httpclient.execute(postRequest) ;
            if (response != null)
        catch (Exception ex)
            ex.printStackTrace() ;
        return null;


Emulate Samsung Galaxy Tab

Matt provided a great link on how to add emulators for all Samsung devices.

To get the official Samsung Galaxy Tab emulator do the following:

  1. Open the Android SDK and AVD Manager
  2. Click on Available packages
  3. Expand the Third party Add-ons. There you will see Samsung Electronics add-ons.
  4. Once the add-on is installed create a new emulator. Under Target you will see the new Samsung Tab settings, select that.

That's it!

How to check if an user is logged in Symfony2 inside a controller?

SecurityContext will be deprecated in Symfony 3.0

Prior to Symfony 2.6 you would use SecurityContext.
SecurityContext will be deprecated in Symfony 3.0 in favour of the AuthorizationChecker.

For Symfony 2.6+ & Symfony 3.0 use AuthorizationChecker.

Symfony 2.6 (and below)

// Get our Security Context Object - [deprecated in 3.0]
$security_context = $this->get('security.context');
# e.g: $security_context->isGranted('ROLE_ADMIN');

// Get our Token (representing the currently logged in user)
$security_token = $security_context->getToken();
# e.g: $security_token->getUser();
# e.g: $security_token->isAuthenticated();
# [Careful]             ^ "Anonymous users are technically authenticated"

// Get our user from that security_token
$user = $security_token->getUser();
# e.g: $user->getEmail(); $user->isSuperAdmin(); $user->hasRole();

// Check for Roles on the $security_context
$isRoleAdmin = $security_context->isGranted('ROLE_ADMIN');
# e.g: (bool) true/false

Symfony 3.0+ (and from Symfony 2.6+)

security.context becomes security.authorization_checker.
We now get our token from security.token_storage instead of the security.context

// [New 3.0] Get our "authorization_checker" Object
$auth_checker = $this->get('security.authorization_checker');
# e.g: $auth_checker->isGranted('ROLE_ADMIN');

// Get our Token (representing the currently logged in user)
// [New 3.0] Get the `token_storage` object (instead of calling upon `security.context`)
$token = $this->get('security.token_storage')->getToken();
# e.g: $token->getUser();
# e.g: $token->isAuthenticated();
# [Careful]            ^ "Anonymous users are technically authenticated"

// Get our user from that token
$user = $token->getUser();
# e.g (w/ FOSUserBundle): $user->getEmail(); $user->isSuperAdmin(); $user->hasRole();

// [New 3.0] Check for Roles on the $auth_checker
$isRoleAdmin = $auth_checker->isGranted('ROLE_ADMIN');
// e.g: (bool) true/false

Read more here in the docs: AuthorizationChecker
How to do this in twig?: Symfony 2: How do I check if a user is not logged in inside a template?

Maven plugin in Eclipse - Settings.xml file is missing

The settings file is never created automatically, you must create it yourself, whether you use embedded or "real" maven.

Create it at the following location <your home folder>/.m2/settings.xml e.g. C:\Users\YourUserName\.m2\settings.xml on Windows or /home/YourUserName/.m2/settings.xml on Linux

Here's an empty skeleton you can use:

<settings xmlns=""

If you use Eclipse to edit it, it will give you auto-completion when editing it.

And here's the Maven settings.xml Reference page

Lambda expression to convert array/List of String to array/List of Integers

You can also use,

List<String> list = new ArrayList<>();

    Integer[] array =
        .map( v -> Integer.valueOf(v))

Str_replace for multiple items

In my use case, I parameterized some fields in an HTML document, and once I load these fields I match and replace them using the str_replace method.

<?php echo str_replace(array("{{client_name}}", "{{client_testing}}"), array('client_company_name', 'test'), 'html_document'); ?>

File opens instead of downloading in internet explorer in a href link

This is not a code issue. It is your default IE settings

To change the "always open" setting:

  1. In Windows Explorer, click on the "Tools" menu, choose "Folder options"
  2. In the window that appears, click on the "File Types" tab, and scroll through the list until you find the file extension you want to change (they're in alphabetical order). For example, if Internet Explorer always tries to open .zip files, scroll through the list until you find the entry for "zip".
  3. Click on the file type, then the "Advanced" button.
  4. Check the "Confirm after download" box, then click OK > Close.

EDIT: If you ask me , instead of making any changes in the code i would add the following text "Internet Explorer users: To download file, "Rightclick" the link and hit "Save target as" to download the file."

EDIT 2: THIS solution will work perfectly for you. Its a solution i just copied from the other answer. Im not trying to pass it off as my own

Content-Type: application/octet-stream
Content-Disposition: attachment;filename=\"\"

However you must make sure that you specify the type of file(s) you allow. You have mentioned in your post that you want this for any type of file. This will be an issue.

For ex. If your site has images and if the end user clicks these images then they will be downloaded on his computer instead of opening in a new page. Got the point. So you need to specify the file extensions.

How do you get the contextPath from JavaScript, the right way?

Reviewer the solution by this Checking the solution of this page, make the following solution I hope it works: Example:


var context = window.location.pathname.substring(0, window.location.pathname.indexOf("/",2)); 
var url =window.location.protocol+"//"+ +context+"/bla/bla";

HTML Display Current date

var currentDate  = new Date(),
    currentDay   = currentDate.getDate() < 10 
                 ? '0' + currentDate.getDate() 
                 : currentDate.getDate(),
    currentMonth = currentDate.getMonth() < 9 
                 ? '0' + (currentDate.getMonth() + 1) 
                 : (currentDate.getMonth() + 1);

document.getElementById("date").innerHTML = currentDay + '/' + currentMonth + '/' +  currentDate.getFullYear();

You can read more about Date object

Mac OS X - EnvironmentError: mysql_config not found

Also this happens when I was installing mysqlclient,

$ pip install mysqlclient

As user3429036 said,

$ brew install mysql

Android : difference between invisible and gone?

For ListView or GridView there is an another difference, when visibility initially set to


Adapter's getView() function called


Adapter's getView() function didn't call, thus preventing views to load, when it is unnecessary

What is the role of "Flatten" in Keras?

It is rule of thumb that the first layer in your network should be the same shape as your data. For example our data is 28x28 images, and 28 layers of 28 neurons would be infeasible, so it makes more sense to 'flatten' that 28,28 into a 784x1. Instead of wriitng all the code to handle that ourselves, we add the Flatten() layer at the begining, and when the arrays are loaded into the model later, they'll automatically be flattened for us.

Format in kotlin string templates

It's simple, use:

val str: String = "%.2f".format(3.14159)

Get and Set Screen Resolution

Answer from different solutions to get Display Resolution

  1. Get the scaling factor

  2. Get Screen.PrimaryScreen.Bounds.Width and Screen.PrimaryScreen.Bounds.Height multiple by scaling factor result

    #region Display Resolution
     [DllImport("gdi32.dll", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
     public static extern int GetDeviceCaps(IntPtr hDC, int nIndex);
     public enum DeviceCap
         VERTRES = 10,
         DESKTOPVERTRES = 117
     public static double GetWindowsScreenScalingFactor(bool percentage = true)
         //Create Graphics object from the current windows handle
         Graphics GraphicsObject = Graphics.FromHwnd(IntPtr.Zero);
         //Get Handle to the device context associated with this Graphics object
         IntPtr DeviceContextHandle = GraphicsObject.GetHdc();
         //Call GetDeviceCaps with the Handle to retrieve the Screen Height
         int LogicalScreenHeight = GetDeviceCaps(DeviceContextHandle, (int)DeviceCap.VERTRES);
         int PhysicalScreenHeight = GetDeviceCaps(DeviceContextHandle, (int)DeviceCap.DESKTOPVERTRES);
         //Divide the Screen Heights to get the scaling factor and round it to two decimals
         double ScreenScalingFactor = Math.Round(PhysicalScreenHeight / (double)LogicalScreenHeight, 2);
         //If requested as percentage - convert it
         if (percentage)
             ScreenScalingFactor *= 100.0;
         //Release the Handle and Dispose of the GraphicsObject object
         //Return the Scaling Factor
         return ScreenScalingFactor;
     public static Size GetDisplayResolution()
         var sf = GetWindowsScreenScalingFactor(false);
         var screenWidth = Screen.PrimaryScreen.Bounds.Width * sf;
         var screenHeight = Screen.PrimaryScreen.Bounds.Height * sf;
         return new Size((int)screenWidth, (int)screenHeight);

to check display resolution

var size = GetDisplayResolution();
Console.WriteLine("Display Resoluton: " + size.Width + "x" + size.Height);

How do emulators work and how are they written?

Emulation is a multi-faceted area. Here are the basic ideas and functional components. I'm going to break it into pieces and then fill in the details via edits. Many of the things I'm going to describe will require knowledge of the inner workings of processors -- assembly knowledge is necessary. If I'm a bit too vague on certain things, please ask questions so I can continue to improve this answer.

Basic idea:

Emulation works by handling the behavior of the processor and the individual components. You build each individual piece of the system and then connect the pieces much like wires do in hardware.

Processor emulation:

There are three ways of handling processor emulation:

  • Interpretation
  • Dynamic recompilation
  • Static recompilation

With all of these paths, you have the same overall goal: execute a piece of code to modify processor state and interact with 'hardware'. Processor state is a conglomeration of the processor registers, interrupt handlers, etc for a given processor target. For the 6502, you'd have a number of 8-bit integers representing registers: A, X, Y, P, and S; you'd also have a 16-bit PC register.

With interpretation, you start at the IP (instruction pointer -- also called PC, program counter) and read the instruction from memory. Your code parses this instruction and uses this information to alter processor state as specified by your processor. The core problem with interpretation is that it's very slow; each time you handle a given instruction, you have to decode it and perform the requisite operation.

With dynamic recompilation, you iterate over the code much like interpretation, but instead of just executing opcodes, you build up a list of operations. Once you reach a branch instruction, you compile this list of operations to machine code for your host platform, then you cache this compiled code and execute it. Then when you hit a given instruction group again, you only have to execute the code from the cache. (BTW, most people don't actually make a list of instructions but compile them to machine code on the fly -- this makes it more difficult to optimize, but that's out of the scope of this answer, unless enough people are interested)

With static recompilation, you do the same as in dynamic recompilation, but you follow branches. You end up building a chunk of code that represents all of the code in the program, which can then be executed with no further interference. This would be a great mechanism if it weren't for the following problems:

  • Code that isn't in the program to begin with (e.g. compressed, encrypted, generated/modified at runtime, etc) won't be recompiled, so it won't run
  • It's been proven that finding all the code in a given binary is equivalent to the Halting problem

These combine to make static recompilation completely infeasible in 99% of cases. For more information, Michael Steil has done some great research into static recompilation -- the best I've seen.

The other side to processor emulation is the way in which you interact with hardware. This really has two sides:

  • Processor timing
  • Interrupt handling

Processor timing:

Certain platforms -- especially older consoles like the NES, SNES, etc -- require your emulator to have strict timing to be completely compatible. With the NES, you have the PPU (pixel processing unit) which requires that the CPU put pixels into its memory at precise moments. If you use interpretation, you can easily count cycles and emulate proper timing; with dynamic/static recompilation, things are a /lot/ more complex.

Interrupt handling:

Interrupts are the primary mechanism that the CPU communicates with hardware. Generally, your hardware components will tell the CPU what interrupts it cares about. This is pretty straightforward -- when your code throws a given interrupt, you look at the interrupt handler table and call the proper callback.

Hardware emulation:

There are two sides to emulating a given hardware device:

  • Emulating the functionality of the device
  • Emulating the actual device interfaces

Take the case of a hard-drive. The functionality is emulated by creating the backing storage, read/write/format routines, etc. This part is generally very straightforward.

The actual interface of the device is a bit more complex. This is generally some combination of memory mapped registers (e.g. parts of memory that the device watches for changes to do signaling) and interrupts. For a hard-drive, you may have a memory mapped area where you place read commands, writes, etc, then read this data back.

I'd go into more detail, but there are a million ways you can go with it. If you have any specific questions here, feel free to ask and I'll add the info.


I think I've given a pretty good intro here, but there are a ton of additional areas. I'm more than happy to help with any questions; I've been very vague in most of this simply due to the immense complexity.

Obligatory Wikipedia links:

General emulation resources:

  • Zophar -- This is where I got my start with emulation, first downloading emulators and eventually plundering their immense archives of documentation. This is the absolute best resource you can possibly have.
  • NGEmu -- Not many direct resources, but their forums are unbeatable.
  • -- The documents section contains resources regarding machine architecture for popular consoles

Emulator projects to reference:

  • IronBabel -- This is an emulation platform for .NET, written in Nemerle and recompiles code to C# on the fly. Disclaimer: This is my project, so pardon the shameless plug.
  • BSnes -- An awesome SNES emulator with the goal of cycle-perfect accuracy.
  • MAME -- The arcade emulator. Great reference.
  • -- This is a JavaScript 6502 emulator with a cool little forum.
  • dynarec'd 6502asm -- This is a little hack I did over a day or two. I took the existing emulator from and changed it to dynamically recompile the code to JavaScript for massive speed increases.

Processor recompilation references:

  • The research into static recompilation done by Michael Steil (referenced above) culminated in this paper and you can find source and such here.


It's been well over a year since this answer was submitted and with all the attention it's been getting, I figured it's time to update some things.

Perhaps the most exciting thing in emulation right now is libcpu, started by the aforementioned Michael Steil. It's a library intended to support a large number of CPU cores, which use LLVM for recompilation (static and dynamic!). It's got huge potential, and I think it'll do great things for emulation.

emu-docs has also been brought to my attention, which houses a great repository of system documentation, which is very useful for emulation purposes. I haven't spent much time there, but it looks like they have a lot of great resources.

I'm glad this post has been helpful, and I'm hoping I can get off my arse and finish up my book on the subject by the end of the year/early next year.

What does "zend_mm_heap corrupted" mean

I was in same situation here, nothing above helped, and checking more seriously I find my problem, it consist in try do die(header()) after send some output to buffer, the man who did this in the Code forgot about CakePHP resources and did not made a simples "return $this->redirect($url)".

Trying to re-invent the well, this was the problem.

I hope this relate help someone!

Bind a function to Twitter Bootstrap Modal Close

Bootstrap 4:

$('#myModal').on('', function (e) {
   // call your method
}) This event is fired immediately when the hide instance method has been called. This event is fired when the modal has finished being hidden from the user (will wait for CSS transitions to complete).

‘ant’ is not recognized as an internal or external command

even with the environment variables set, I found that ant -version does not work in scripts. Try call ant -version

How to sum all values in a column in Jaspersoft iReport Designer?

iReports Custom Fields for columns (sum, average, etc)

  1. Right-Click on Variables and click Create Variable

  2. Click on the new variable

    a. Notice the properties on the right

  3. Rename the variable accordingly

  4. Change the Value Class Name to the correct Data Type

    a. You can search by clicking the 3 dots

  5. Select the correct type of calculation

  6. Change the Expression

    a. Click the little icon

    b. Select the column you are looking to do the calculation for

    c. Click finish

  7. Set Initial Value Expression to 0

  8. Set the increment type to none

  9. Leave Incrementer Factory Class Name blank
  10. Set the Reset Type (usually report)

  11. Drag a new Text Field to stage (Usually in Last Page Footer, or Column Footer)

  12. Double Click the new Text Field
  13. Clear the expression “Text Field”
  14. Select the new variable

  15. Click finish

  16. Put the new text in a desirable position ?

Javascript Array Alert

If you want to see the array as an array, you can say


instead of all those document.writes.

However, if you want to display them cleanly, one per line, in your popup, do this:


Converting a Date object to a calendar object

Here's your method:

public static Calendar toCalendar(Date date){ 
  Calendar cal = Calendar.getInstance();
  return cal;

Everything else you are doing is both wrong and unnecessary.

BTW, Java Naming conventions suggest that method names start with a lower case letter, so it should be: dateToCalendar or toCalendar (as shown).

OK, let's milk your code, shall we?

DateFormat formatter = new SimpleDateFormat("yyyyMMdd");
date = (Date)formatter.parse(date.toString()); 

DateFormat is used to convert Strings to Dates (parse()) or Dates to Strings (format()). You are using it to parse the String representation of a Date back to a Date. This can't be right, can it?

How to truncate a foreign key constrained table?

Yes you can:


TRUNCATE table1;
TRUNCATE table2;


With these statements, you risk letting in rows into your tables that do not adhere to the FOREIGN KEY constraints.

Testing for empty or nil-value string

The second clause does not need a !variable.nil? check—if evaluation reaches that point, variable.nil is guaranteed to be false (because of short-circuiting).

This should be sufficient:

variable = id if variable.nil? || variable.empty?

If you're working with Ruby on Rails, Object.blank? solves this exact problem:

An object is blank if it’s false, empty, or a whitespace string. For example, "", " ", nil, [], and {} are all blank.

what is Ljava.lang.String;@

I also met this problem when I've made ListView for android app:

Map<String, Object> m;

for(int i=0; i < dates.length; i++){
    m = new HashMap<String, Object>();
    m.put(ATTR_DATES, dates[i]);
    m.put(ATTR_SQUATS, squats[i]);
    m.put(ATTR_BP, benchpress[i]);
    m.put(ATTR_ROW, row[i]);

The problem was that I've forgotten to use the [i] index inside the loop

SQL Server 2008: TOP 10 and distinct together

The easy option is to use group by and select min/max for all other fields

    dm.labs pl
    mas_data.patients p    
on =
    pl.nm like '%LDL%'
    val is not null
group by

This can get quite tedious for wide table so the other option is to use rank over and partiion

    rank() over(partition by order by as Rank
    dm.labs pl
    mas_data.patients p    
on =
    pl.nm like '%LDL%'
    val is not null
    Rank = 1

How to return more than one value from a function in Python?

You separate the values you want to return by commas:

def get_name():
   # you code
   return first_name, last_name

The commas indicate it's a tuple, so you could wrap your values by parentheses:

return (first_name, last_name)

Then when you call the function you a) save all values to one variable as a tuple, or b) separate your variable names by commas

name = get_name() # this is a tuple
first_name, last_name = get_name()
(first_name, last_name) = get_name() # You can put parentheses, but I find it ugly

Table column sizing

Another option is to apply flex styling at the table row, and add the col-classes to the table header / table data elements:

    <tr class="d-flex">
      <th class="col-3">3 columns wide header</th>
      <th class="col-sm-5">5 columns wide header</th>
      <th class="col-sm-4">4 columns wide header</th>
    <tr class="d-flex">
      <td class="col-3">3 columns wide content</th>
      <td class="col-sm-5">5 columns wide content</th>
      <td class="col-sm-4">4 columns wide content</th>

Generating a unique machine id

I hate to be the guy who says, "you're just doing it wrong" (I always hate that guy ;) but...

Does it have to be repeatably generated for the unique machine? Could you just assign the identifier or do a public/private key? Maybe if you could generate and store the value, you could access it from both OS installs on the same disk?

You've probably explored these options and they doesn't work for you, but if not, it's something to consider.

If it's not a matter of user trust, you could just use MAC addresses.

String.format() to format double in java

There are many way you can do this. Those are given bellow:

Suppose your original number is given bellow: double number = 2354548.235;

Using NumberFormat and Rounding mode

NumberFormat nf = DecimalFormat.getInstance(Locale.ENGLISH);
    DecimalFormat decimalFormatter = (DecimalFormat) nf;

    String fString = decimalFormatter.format(number);

Using String formatter

System.out.println(String.format("%1$,.2f", number));

In all cases the output will be: 2354548.24


During rounding you can add RoundingMode in your formatter. Here are some Rounding mode given bellow:


Here are the imports:

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.Locale;

groovy.lang.MissingPropertyException: No such property: jenkins for class: groovy.lang.Binding

Please double check that jenkins is not blocking this import. Go to script approvals and check to see if it is blocking it. If it is click allow.

What is the difference between old style and new style classes in Python?

From New-style and classic classes:

Up to Python 2.1, old-style classes were the only flavour available to the user.

The concept of (old-style) class is unrelated to the concept of type: if x is an instance of an old-style class, then x.__class__ designates the class of x, but type(x) is always <type 'instance'>.

This reflects the fact that all old-style instances, independently of their class, are implemented with a single built-in type, called instance.

New-style classes were introduced in Python 2.2 to unify the concepts of class and type. A new-style class is simply a user-defined type, no more, no less.

If x is an instance of a new-style class, then type(x) is typically the same as x.__class__ (although this is not guaranteed – a new-style class instance is permitted to override the value returned for x.__class__).

The major motivation for introducing new-style classes is to provide a unified object model with a full meta-model.

It also has a number of immediate benefits, like the ability to subclass most built-in types, or the introduction of "descriptors", which enable computed properties.

For compatibility reasons, classes are still old-style by default.

New-style classes are created by specifying another new-style class (i.e. a type) as a parent class, or the "top-level type" object if no other parent is needed.

The behaviour of new-style classes differs from that of old-style classes in a number of important details in addition to what type returns.

Some of these changes are fundamental to the new object model, like the way special methods are invoked. Others are "fixes" that could not be implemented before for compatibility concerns, like the method resolution order in case of multiple inheritance.

Python 3 only has new-style classes.

No matter if you subclass from object or not, classes are new-style in Python 3.

How to open the Chrome Developer Tools in a new window?

If you need to open the DevTools press ctrl-shift-i.

If the DevTools window is already opened you can use the ctrl-shift-d shortcut; it switches the window into a detached mode.

For example in my case the electron application window (Chrome) is really small.

enter image description here

It's not possible to use any other suggestions except the ctrl-shift-d shortcut

How to replace NaN value with zero in a huge data frame?

The following should do what you want:

x <- data.frame(X1=sample(c(1:3,NaN), 200, replace=TRUE), X2=sample(c(4:6,NaN), 200, replace=TRUE))
x <- replace(x,, 0)

SQL Server - Convert varchar to another collation (code page) to fix character encoding

I think SELECT CAST( CAST([field] AS VARBINARY(120)) AS varchar(120)) for your update

How does the enhanced for statement work for arrays, and how to get an iterator for an array?

If you want an Iterator over an array, you could use one of the direct implementations out there instead of wrapping the array in a List. For example:

Apache Commons Collections ArrayIterator

Or, this one, if you'd like to use generics:


Note that if you want to have an Iterator over primitive types, you can't, because a primitive type can't be a generic parameter. E.g., if you want an Iterator<int>, you have to use an Iterator<Integer> instead, which will result in a lot of autoboxing and -unboxing if that's backed by an int[].

OpenVPN failed connection / All TAP-Win32 adapters on this system are currently in use

It seems to me you are using the wrong version...

TAP-Win32 should not be installed on the 64bit version. Download the right one and try again!

What are the new features in C++17?

Language features:

Templates and Generic Code



Syntax cleanup

Cleaner multi-return and flow control

  • Structured bindings

    • Basically, first-class std::tie with auto
    • Example:
      • const auto [it, inserted] = map.insert( {"foo", bar} );
      • Creates variables it and inserted with deduced type from the pair that map::insert returns.
    • Works with tuple/pair-likes & std::arrays and relatively flat structs
    • Actually named structured bindings in standard
  • if (init; condition) and switch (init; condition)

    • if (const auto [it, inserted] = map.insert( {"foo", bar} ); inserted)
    • Extends the if(decl) to cases where decl isn't convertible-to-bool sensibly.
  • Generalizing range-based for loops

    • Appears to be mostly support for sentinels, or end iterators that are not the same type as begin iterators, which helps with null-terminated loops and the like.
  • if constexpr

    • Much requested feature to simplify almost-generic code.


Library additions:

Data types

Invoke stuff

File System TS v1

New algorithms

  • for_each_n

  • reduce

  • transform_reduce

  • exclusive_scan

  • inclusive_scan

  • transform_exclusive_scan

  • transform_inclusive_scan

  • Added for threading purposes, exposed even if you aren't using them threaded


(parts of) Library Fundamentals TS v1 not covered above or below

Container Improvements

Smart pointer changes

Other std datatype improvements:



Deprecated has has an independent list of changes since C++14; it has been partly pillaged.

Naturally TS work continues in parallel, so there are some TS that are not-quite-ripe that will have to wait for the next iteration. The target for the next iteration is C++20 as previously planned, not C++19 as some rumors implied. C++1O has been avoided.

Initial list taken from this reddit post and this reddit post, with links added via googling or from the above page.

Additional entries pillaged from SD-6 feature-test list.

clang's feature list and library feature list are next to be pillaged. This doesn't seem to be reliable, as it is C++1z, not C++17.

these slides had some features missing elsewhere.

While "what was removed" was not asked, here is a short list of a few things ((mostly?) previous deprecated) that are removed in C++17 from C++:


There were rewordings. I am unsure if these have any impact on code, or if they are just cleanups in the standard:

Papers not yet integrated into above:

  • P0505R0 (constexpr chrono)

  • P0418R2 (atomic tweaks)

  • P0512R0 (template argument deduction tweaks)

  • P0490R0 (structured binding tweaks)

  • P0513R0 (changes to std::hash)

  • P0502R0 (parallel exceptions)

  • P0509R1 (updating restrictions on exception handling)

  • P0012R1 (make exception specifications be part of the type system)

  • P0510R0 (restrictions on variants)

  • P0504R0 (tags for optional/variant/any)

  • P0497R0 (shared ptr tweaks)

  • P0508R0 (structured bindings node handles)

  • P0521R0 (shared pointer use count and unique changes?)

Spec changes:

Further reference:

How to create a testflight invitation code?

after you add the user for testing. the user should get an email. open that email by your iOS device, then click "Start testing" it will bring you to testFlight to download the app directly. If you open that email via computer, and then click "Start testing" it will show you another page which have the instruction of how to install the app. and that invitation code is on the last line. those All upper case letters is the code.

Uses for the '&quot;' entity in HTML

It is likely because they used a single function for escaping attributes and text nodes. &amp; doesn't do any harm so why complicate your code and make it more error-prone by having two escaping functions and having to pick between them?

100% width background image with an 'auto' height

You can use the CSS property background-size and set it to cover or contain, depending your preference. Cover will cover the window entirely, while contain will make one side fit the window thus not covering the entire page (unless the aspect ratio of the screen is equal to the image).

Please note that this is a CSS3 property. In older browsers, this property is ignored. Alternatively, you can use javascript to change the CSS settings depending on the window size, but this isn't preferred.

body {
    background-image: url(image.jpg); /* image */
    background-position: center;      /* center the image */
    background-size: cover;           /* cover the entire window */

"Incorrect string value" when trying to insert UTF-8 into MySQL via JDBC?

If you are creating a new MySQL table, you can specify the charset of all columns upon creation, and that fixed the issue for me.

CREATE TABLE tablename (
CHARSET SET utf8mb4 COLLATE utf8mb4_unicode_ci;

You can read more details:

Coding Conventions - Naming Enums

This will probably not make me a lot of new friends, but it should be added that the C# people have a different guideline: The enum instances are "Pascal case" (upper/lower case mixed). See stackoverflow discussion and MSDN Enumeration Type Naming Guidelines.

As we are exchanging data with a C# system, I am tempted to copy their enums exactly, ignoring Java's "constants have uppercase names" convention. Thinking about it, I don't see much value in being restricted to uppercase for enum instances. For some purposes .name() is a handy shortcut to get a readable representation of an enum constant and a mixed case name would look nicer.

So, yes, I dare question the value of the Java enum naming convention. The fact that "the other half of the programming world" does indeed use a different style makes me think it is legitimate to doubt our own religion.

Is it possible to declare a variable in Gradle usable in Java? Answer by @rciovati works

But make sure you rebuild the project to be able to remove the error from Android Studio IDE

I spent 30 minutes trying to figure out why the new property variables aren't accessible.

If the "Make Project" as marked with red color doesn't work then try the "Rebuild Project" Button as marked with green color.

enter image description here

How to open a local disk file with JavaScript?

Javascript cannot typically access local files in new browsers but the XMLHttpRequest object can be used to read files. So it is actually Ajax (and not Javascript) which is reading the file.

If you want to read the file abc.txt, you can write the code as:

var txt = '';
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function(){
  if(xmlhttp.status == 200 && xmlhttp.readyState == 4){
    txt = xmlhttp.responseText;

Now txt contains the contents of the file abc.txt.

SOAP vs REST (differences)

What is REST

REST stands for representational state transfer, it's actually an architectural style for creating Web API which treats everything(data or functionality) as recourse. It expects; exposing resources through URI and responding in multiple formats and representational transfer of state of the resources in stateless manner. Here I am talking about two things:

  1. Stateless manner: Provided by HTTP.
  2. Representational transfer of state: For example if we are adding an employee. . into our system, it's in POST state of HTTP, after this it would be in GET state of HTTP, PUT and DELETE likewise.

REST can use SOAP web services because it is a concept and can use any protocol like HTTP, SOAP.SOAP uses services interfaces to expose the business logic. REST uses URI to expose business logic.

REST is not REST without HATEOAS. This means that a client only knows the entry point URI and the resources are supposed to return links the client should follow. Those fancy documentation generators that give URI patterns for everything you can do in a REST API miss the point completely. They are not only documenting something that's supposed to be following the standard, but when you do that, you're coupling the client to one particular moment in the evolution of the API, and any changes on the API have to be documented and applied, or it will break.

HATEOAS, an abbreviation for Hypermedia As The Engine Of Application State, is a constraint of the REST application architecture that distinguishes it from most other network application architectures. The principle is that a client interacts with a network application entirely through hypermedia provided dynamically by application servers. A REST client needs no prior knowledge about how to interact with any particular application or server beyond a generic understanding of hypermedia. By contrast, in some service-oriented architectures (SOA), clients and servers interact through a fixed interface shared through documentation or an interface description language (IDL).

Reference 1 Reference 2

SHA-256 or MD5 for file integrity

  1. Yes, on most CPUs, SHA-256 is two to three times slower than MD5, though not primarily because of its longer hash. See other answers here and the answers to this Stack Overflow questions.
  2. Here's a backup scenario where MD5 would not be appropriate:
    • Your backup program hashes each file being backed up. It then stores each file's data by its hash, so if you're backing up the same file twice you only end up with one copy of it.
    • An attacker can cause the system to backup files they control.
    • The attacker knows the MD5 hash of a file they want to remove from the backup.
    • The attacker can then use the known weaknesses of MD5 to craft a new file that has the same hash as the file to remove. When that file is backed up, it will replace the file to remove, and that file's backed up data will be lost.
    • This backup system could be strengthened a bit (and made more efficient) by not replacing files whose hash it has previously encountered, but then an attacker could prevent a target file with a known hash from being backed up by preemptively backing up a specially constructed bogus file with the same hash.
    • Obviously most systems, backup and otherwise, do not satisfy the conditions necessary for this attack to be practical, but I just wanted to give an example of a situation where SHA-256 would be preferable to MD5. Whether this would be the case for the system you're creating depends on more than just the characteristics of MD5 and SHA-256.
  3. Yes, cryptographic hashes like the ones generated by MD5 and SHA-256 are a type of checksum.

Happy hashing!

Get a UTC timestamp

new Date().getTime();

For more information, see @James McMahon's answer.

Python foreach equivalent

Its also interesting to observe this

To iterate over the indices of a sequence, you can combine range() and len() as follows:

a = ['Mary', 'had', 'a', 'little', 'lamb']
for i in range(len(a)):
  print(i, a[i])


0 Mary
1 had
2 a
3 little
4 lamb

Edit#1: Alternate way:

When looping through a sequence, the position index and corresponding value can be retrieved at the same time using the enumerate() function.

for i, v in enumerate(['tic', 'tac', 'toe']):
  print(i, v)


0 tic
1 tac
2 toe

With Twitter Bootstrap, how can I customize the h1 text color of one page and leave the other pages to be default?

you could use the font style Like:

     <font color="white"><h1>Header Content</h1></font>

Peak-finding algorithm for Python/SciPy

The function scipy.signal.find_peaks, as its name suggests, is useful for this. But it's important to understand well its parameters width, threshold, distance and above all prominence to get a good peak extraction.

According to my tests and the documentation, the concept of prominence is "the useful concept" to keep the good peaks, and discard the noisy peaks.

What is (topographic) prominence? It is "the minimum height necessary to descend to get from the summit to any higher terrain", as it can be seen here:

enter image description here

The idea is:

The higher the prominence, the more "important" the peak is.


enter image description here

I used a (noisy) frequency-varying sinusoid on purpose because it shows many difficulties. We can see that the width parameter is not very useful here because if you set a minimum width too high, then it won't be able to track very close peaks in the high frequency part. If you set width too low, you would have many unwanted peaks in the left part of the signal. Same problem with distance. threshold only compares with the direct neighbours, which is not useful here. prominence is the one that gives the best solution. Note that you can combine many of these parameters!


import numpy as np
import matplotlib.pyplot as plt 
from scipy.signal import find_peaks

x = np.sin(2*np.pi*(2**np.linspace(2,10,1000))*np.arange(1000)/48000) + np.random.normal(0, 1, 1000) * 0.15
peaks, _ = find_peaks(x, distance=20)
peaks2, _ = find_peaks(x, prominence=1)      # BEST!
peaks3, _ = find_peaks(x, width=20)
peaks4, _ = find_peaks(x, threshold=0.4)     # Required vertical distance to its direct neighbouring samples, pretty useless
plt.subplot(2, 2, 1)
plt.plot(peaks, x[peaks], "xr"); plt.plot(x); plt.legend(['distance'])
plt.subplot(2, 2, 2)
plt.plot(peaks2, x[peaks2], "ob"); plt.plot(x); plt.legend(['prominence'])
plt.subplot(2, 2, 3)
plt.plot(peaks3, x[peaks3], "vg"); plt.plot(x); plt.legend(['width'])
plt.subplot(2, 2, 4)
plt.plot(peaks4, x[peaks4], "xk"); plt.plot(x); plt.legend(['threshold'])

Google Maps API Multiple Markers with Infowindows

Here is the code snippet which will work for sure. You can visit below link for working jsFiddle and explainantion in detail. How to locate multiple addresses on google maps with perfect zoom

var infowindow = new google.maps.InfoWindow();  
google.maps.event.addListener(marker, 'mouseover', (function(marker) {  
           return function() {  
               var content = address;  
     , marker);  

How to write std::string to file?

remove the ios::binary from your modes in your ofstream and use studentPassword.c_str() instead of (char *)&studentPassword in your write.write()

XPath OR operator for different nodes

All title nodes with zipcode or book node as parent:

Version 1:


Version 2:


Version 3: (results are sorted based on source data rather than the order of book then zipcode)

//title[../../../*[book or magazine] or ../../../../*[city/zipcode]]

or - used within true/false - a Boolean operator in xpath

| - a Union operator in xpath that appends the query to the right of the operator to the result set from the left query.

How to export database schema in Oracle to a dump file

It depends on which version of Oracle? Older versions require exp (export), newer versions use expdp (data pump); exp was deprecated but still works most of the time.

Before starting, note that Data Pump exports to the server-side Oracle "directory", which is an Oracle symbolic location mapped in the database to a physical location. There may be a default directory (DATA_PUMP_DIR), check by querying DBA_DIRECTORIES:

  SQL> select * from dba_directories;

... and if not, create one

  SQL> create directory DATA_PUMP_DIR as '/oracle/dumps';
  SQL> grant all on directory DATA_PUMP_DIR to myuser;    -- DBAs dont need this grant

Assuming you can connect as the SYSTEM user, or another DBA, you can export any schema like so, to the default directory:

 $ expdp system/manager schemas=user1 dumpfile=user1.dpdmp

Or specifying a specific directory, add directory=<directory name>:

 C:\> expdp system/manager schemas=user1 dumpfile=user1.dpdmp directory=DUMPDIR

With older export utility, you can export to your working directory, and even on a client machine that is remote from the server, using:

 $ exp system/manager owner=user1 file=user1.dmp

Make sure the export is done in the correct charset. If you haven't setup your environment, the Oracle client charset may not match the DB charset, and Oracle will do charset conversion, which may not be what you want. You'll see a warning, if so, then you'll want to repeat the export after setting NLS_LANG environment variable so the client charset matches the database charset. This will cause Oracle to skip charset conversion.

Example for American UTF8 (UNIX):


Windows uses SET, example using Japanese UTF8:

 C:\> set NLS_LANG=Japanese_Japan.AL32UTF8

More info on Data Pump here:

Whoops, looks like something went wrong. Laravel 5.0

make sure app/storage dir permission is set to 755 and owner is set to admin. and also check permission and owner of files and dir in app/storage too

How to set focus on input field?

  1. When a Modal is opened, set focus on a predefined <input> inside this Modal.

Define a directive and have it $watch a property/trigger so it knows when to focus the element:

Name: <input type="text" focus-me="shouldBeOpen">

app.directive('focusMe', ['$timeout', '$parse', function ($timeout, $parse) {
    return {
        //scope: true,   // optionally create a child scope
        link: function (scope, element, attrs) {
            var model = $parse(attrs.focusMe);
            scope.$watch(model, function (value) {
                console.log('value=', value);
                if (value === true) {
                    $timeout(function () {
            // to address @blesh's comment, set attribute value to 'false'
            // on blur event:
            element.bind('blur', function () {
                scope.$apply(model.assign(scope, false));


The $timeout seems to be needed to give the modal time to render.

'2.' Everytime <input> becomes visible (e.g. by clicking some button), set focus on it.

Create a directive essentially like the one above. Watch some scope property, and when it becomes true (set it in your ng-click handler), execute element[0].focus(). Depending on your use case, you may or may not need a $timeout for this one:

<button class="btn" ng-click="showForm=true; focusInput=true">show form and
 focus input</button>
<div ng-show="showForm">
  <input type="text" ng-model="myInput" focus-me="focusInput"> {{ myInput }}
  <button class="btn" ng-click="showForm=false">hide form</button>

app.directive('focusMe', function($timeout) {
  return {
    link: function(scope, element, attrs) {
      scope.$watch(attrs.focusMe, function(value) {
        if(value === true) { 
          //$timeout(function() {
            scope[attrs.focusMe] = false;


Update 7/2013: I've seen a few people use my original isolate scope directives and then have problems with embedded input fields (i.e., an input field in the modal). A directive with no new scope (or possibly a new child scope) should alleviate some of the pain. So above I updated the answer to not use isolate scopes. Below is the original answer:

Original answer for 1., using an isolate scope:

Name: <input type="text" focus-me="{{shouldBeOpen}}">

app.directive('focusMe', function($timeout) {
  return {
    scope: { trigger: '@focusMe' },
    link: function(scope, element) {
      scope.$watch('trigger', function(value) {
        if(value === "true") { 
          $timeout(function() {


Original answer for 2., using an isolate scope:

<button class="btn" ng-click="showForm=true; focusInput=true">show form and
 focus input</button>
<div ng-show="showForm">
  <input type="text" focus-me="focusInput">
  <button class="btn" ng-click="showForm=false">hide form</button>

app.directive('focusMe', function($timeout) {
  return {
    scope: { trigger: '=focusMe' },
    link: function(scope, element) {
      scope.$watch('trigger', function(value) {
        if(value === true) { 
          //$timeout(function() {
            scope.trigger = false;


Since we need to reset the trigger/focusInput property in the directive, '=' is used for two-way databinding. In the first directive, '@' was sufficient. Also note that when using '@' we compare the trigger value to "true" since @ always results in a string.

Laravel Request getting current path with query string

Try to use the following:


How to I say Is Not Null in VBA

Use Not IsNull(Fields!W_O_Count.Value)

jQuery: Check if button is clicked

$('#submit1, #submit2').click(function () {
   if ( == 'submit1') {
      alert('Submit 1 clicked');
   else if ( == 'submit2') {
      alert('Submit 2 clicked');

Unable to execute dex: Multiple dex files define

  • Right click on project and go to build Path>configuration build path
  • Select library tab and click on support-v4 library and click on remove
  • Click on OK

and then clean your project and run it will work :-)

How to add LocalDB to Visual Studio 2015 Community's SQL Server Object Explorer?

If you are not sure if local db is installed, or not sure which database name you should use to connect to it - try running 'sqllocaldb info' command - it will show you existing localdb databases.

Now, as far as I know, local db should be installed together with Visual Studio 2015. But probably it is not required feature, and if something goes wrong or it cannot be installed for some reason - Visual Studio installation continues still (note that is just my guess). So to be on the safe side don't rely on it will always be installed together with VS.

Visual Studio keyboard shortcut to display IntelliSense

The most efficient one is Ctrl + ..

It helps to automate insertions of using directives. It works if the focus is on a new identifier, e.g. class name.

Another git process seems to be running in this repository

I tried deleting .git/indexbut didn't work, I end up uninstalling go and removing all folders that has go name in it, and then installing go again, and it workerd!

Run cmd commands through Java

Stopping and Disabling a service can be done via below code:

static void sdService() {
    String[] cmd = {"cmd.exe", "/c", "net", "stop", "MSSQLSERVER"};
    try {           
        Process process = new ProcessBuilder(cmd).start();
        String line = null;
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(process.getInputStream()));
        while((line = bufferedReader.readLine()) != null) {
        line = null;
        bufferedReader = null;
        Process p = Runtime.getRuntime().exec("sc config MSSQLSERVER start= disabled");
        bufferedReader = new BufferedReader(new InputStreamReader(p.getInputStream()));
        while((line = bufferedReader.readLine()) != null) {
    } catch (Exception e) {

Enabling and Starting a service can be done via below code

static void esService() {
    String[] cmd = {"cmd.exe", "/c", "net", "start", "MSSQLSERVER"};
    try {
        Process p = Runtime.getRuntime().exec("sc config MSSQLSERVER start= auto");
        //Process p = Runtime.getRuntime().exec("sc config MSSQLSERVER start= demand");
        String line = null;
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(p.getInputStream()));
        while((line = bufferedReader.readLine()) != null) {
        line = null;
        bufferedReader = null;
        Process process = new ProcessBuilder(cmd).start();          
        bufferedReader = new BufferedReader(new InputStreamReader(process.getInputStream()));
        while((line = bufferedReader.readLine()) != null) {
    } catch (Exception e) {

Executing command from any folder can be done via below code.

static void runFromSpecificFolder() {       
    try {
        ProcessBuilder processBuilder = new ProcessBuilder("cmd.exe", "/c", "cd \"C:\\Users\\himan\\Desktop\\Java_Test_Deployment\\jarfiles\" && dir");
        // File("C://Users//himan//Desktop//Java_Test_Deployment//jarfiles"));
        Process p = processBuilder.start();
        String line = null;
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(p.getInputStream()));
        while((line = bufferedReader.readLine()) != null) {
    } catch (Exception e) {
public static void main(String args[]) {

PHP to search within txt file and echo the whole line

looks like you're better off systeming out to system("grep \"$QUERY\"") since that script won't be particularly high performance either way. Otherwise shows you how to loop over lines and you can use for finding matches.

How to use Git Revert

The reason reset and revert tend to come up a lot in the same conversations is because different version control systems use them to mean different things.

In particular, people who are used to SVN or P4 who want to throw away uncommitted changes to a file will often reach for revert before being told that they actually want reset.

Similarly, the revert equivalent in other VCSes is often called rollback or something similar - but "rollback" can also mean "I want to completely discard the last few commits", which is appropriate for reset but not revert. So, there's a lot of confusion where people know what they want to do, but aren't clear on which command they should be using for it.

As for your actual questions about revert...

Okay, you're going to use git revert but how?

git revert first-bad-commit..last-bad-commit

And after running git revert do you have to do something else after? Do you have to commit the changes revert made or does revert directly commit to the repo or what??

By default, git revert prompts you for a commit message and then commits the results. This can be overridden. I quote the man page:


With this option, git revert will let you edit the commit message prior to committing the revert. This is the default if you run the command from a terminal.


Usually the command automatically creates some commits with commit log messages stating which commits were reverted. This flag applies the changes necessary to revert the named commits to your working tree and the index, but does not make the commits. In addition, when this option is used, your index does not have to match the HEAD commit. The revert is done against the beginning state of your index.

This is useful when reverting more than one commits' effect to your index in a row.

In particular, by default it creates a new commit for each commit you're reverting. You can use revert --no-commit to create changes reverting all of them without committing those changes as individual commits, then commit at your leisure.

How to build splash screen in windows forms application?

Here are some guideline steps...

  1. Create a borderless form (this will be your splash screen)
  2. On application start, start a timer (with a few seconds interval)
  3. Show your Splash Form
  4. On Timer.Tick event, stop timer and close Splash form - then show your main application form

Give this a go and if you get stuck then come back and ask more specific questions relating to your problems