Android - How to download a file from a webserver

Question

In my app I am downloading a kml file from a webserver  I have set the permission for external storage and internet in my android manifest file  I am new to Android  your help is greatly appreciated   MainActivity java  package com example demo   import java io DataInputStream  import java io File  import java io FileOutputStream  import java io IOException  import java io InputStream  import java net MalformedURLException  import java net URL   import android app Activity  import android os Bundle  import android os Environment  import android util Log  import android view Menu   public class MainActivity extends Activity         Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout activity main            DownloadFiles               public void DownloadFiles            try               URL u   new URL  http   www qwikisoft com demo ashade 20001 kml                InputStream is   u openStream                DataInputStream dis   new DataInputStream is                byte   buffer   new byte 1024               int length               FileOutputStream fos   new FileOutputStream new File Environment getExternalStorageDirectory            data test kml                 while   length   dis read buffer    gt  0                    fos write buffer  0  length                            catch  MalformedURLException mue                Log e  SYNC getUpdate    malformed url error   mue             catch  IOException ioe                Log e  SYNC getUpdate    io error   ioe             catch  SecurityException se                Log e  SYNC getUpdate    security error   se                       Android Manifest File   lt  xml version  1 0  encoding  utf-8   gt   lt manifest xmlns android  http   schemas android com apk res android      package  com example demo      android versionCode  1      android versionName  1 0   gt        lt uses-sdk         android minSdkVersion  8          android targetSdkVersion  16    gt       lt uses-permission android name  android permission INTERNET   gt       lt uses-permission android name  android permission WRITE EXTERNAL STORAGE   gt        lt application         android allowBackup  true          android icon   drawable ic launcher          android label   string app name          android theme   style AppTheme   gt            lt activity             android name  com example demo MainActivity              android label   string app name   gt               lt intent-filter gt                   lt action android name  android intent action MAIN    gt                    lt category android name  android intent category LAUNCHER    gt               lt  intent-filter gt           lt  activity gt       lt  application gt   lt  manifest gt    Logcat error      FATAL EXCEPTION  main       java lang RuntimeException  Unable to start activity ComponentInfo com example demo com example demo MainActivity   android os NetworkOnMainThreadException       at android app ActivityThread performLaunchActivity ActivityThread java 1956        at android app ActivityThread handleLaunchActivity ActivityThread java 1981        at android app ActivityThread access 600 ActivityThread java 123        at android app ActivityThread H handleMessage ActivityThread java 1147        at android os Handler dispatchMessage Handler java 99        at android os Looper loop Looper java 137        at android app ActivityThread main ActivityThread java 4424        at java lang reflect Method invokeNative Native Method        at java lang reflect Method invoke Method java 511        at com android internal os ZygoteInit MethodAndArgsCaller run ZygoteInit java 784        at com android internal os ZygoteInit main ZygoteInit java 551        at dalvik system NativeStart main Native Method        Caused by  android os NetworkOnMainThreadException       at android os StrictMode AndroidBlockGuardPolicy onNetwork StrictMode java 1099        at java net InetAddress lookupHostByName InetAddress java 391        at java net InetAddress getAllByNameImpl InetAddress java 242        at java net InetAddress getAllByName InetAddress java 220        at libcore net http HttpConnection  HttpConnection java 71        at libcore net http HttpConnection  HttpConnection java 50        at libcore net http HttpConnection Address connect HttpConnection java 351        at libcore net http HttpConnectionPool get HttpConnectionPool java 86        at libcore net http HttpConnection connect HttpConnection java 128        at libcore net http HttpEngine openSocketConnection HttpEngine java 308        at libcore net http HttpEngine connect HttpEngine java 303        at libcore net http HttpEngine sendSocketRequest HttpEngine java 282        at libcore net http HttpEngine sendRequest HttpEngine java 232        at libcore net http HttpURLConnectionImpl getResponse HttpURLConnectionImpl java 273        at libcore net http HttpURLConnectionImpl getInputStream HttpURLConnectionImpl java 168        at java net URL openStream URL java 462        at com example demo MainActivity DownloadFiles MainActivity java 30        at com example demo MainActivity onCreate MainActivity java 24        at android app Activity performCreate Activity java 4465        at android app Instrumentation callActivityOnCreate Instrumentation java 1049        at android app ActivityThread performLaunchActivity ActivityThread java 1920    EDIT  package com example demo   import java io BufferedInputStream  import java io FileOutputStream  import java io InputStream  import java io OutputStream  import java net URL  import java net URLConnection   import android app Activity  import android app Dialog  import android app ProgressDialog  import android os AsyncTask  import android os Bundle  import android os Environment  import android util Log   public class MainActivity extends Activity        private ProgressDialog pDialog      public static final int progress bar type   0        Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout activity main            new DownloadFileFromURL   execute  http   www qwikisoft com demo ashade 20001 kml                Override     protected Dialog onCreateDialog int id            switch  id                case progress bar type     we set this to 0                 pDialog   new ProgressDialog this                   pDialog setMessage  Downloading file  Please wait                       pDialog setIndeterminate false                   pDialog setMax 100                   pDialog setProgressStyle ProgressDialog STYLE HORIZONTAL                   pDialog setCancelable true                   pDialog show                    return pDialog              default                  return null                       class DownloadFileFromURL extends AsyncTask lt String  String  String gt                            Before starting background thread Show Progress Bar Dialog                       Override         protected void onPreExecute                 super onPreExecute                showDialog progress bar type                                     Downloading file in background thread                       Override         protected String doInBackground String    f url                int count              try                   URL url   new URL f url 0                    URLConnection conection   url openConnection                    conection connect                        this will be useful so that you can show a tipical 0-100                     progress bar                 int lenghtOfFile   conection getContentLength                        download the file                 InputStream input   new BufferedInputStream url openStream                            8192                       Output stream                 OutputStream output   new FileOutputStream Environment                          getExternalStorageDirectory   toString                               data downloadedfile kml                     byte data     new byte 1024                    long total   0                   while   count   input read data      -1                        total    count                         publishing the progress                            After this onProgressUpdate will be called                     publishProgress       int    total   100    lenghtOfFile                            writing data to file                     output write data  0  count                                         flushing output                 output flush                        closing streams                 output close                    input close                  catch  Exception e                    Log e  Error     e getMessage                                return null                                    Updating progress bar                      protected void onProgressUpdate String    progress                   setting progress percentage             pDialog setProgress Integer parseInt progress 0                                       After completing background task Dismiss the progress dialog                       Override         protected void onPostExecute String file url                   dismiss the dialog after the file was downloaded             dismissDialog progress bar type                       When I run this code in the emulator the code still does not work - the file is not getting downloaded

User · Accepted Answer

Using Async task

call when you want to download file : new DownloadFileFromURL().execute(file_url);

public class MainActivity extends Activity {

    // Progress Dialog
    private ProgressDialog pDialog;
    public static final int progress_bar_type = 0;

    // File url to download
    private static String file_url = "http://www.qwikisoft.com/demo/ashade/20001.kml";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        new DownloadFileFromURL().execute(file_url);

    }

    /**
     * Showing Dialog
     * */

    @Override
    protected Dialog onCreateDialog(int id) {
        switch (id) {
        case progress_bar_type: // we set this to 0
            pDialog = new ProgressDialog(this);
            pDialog.setMessage("Downloading file. Please wait...");
            pDialog.setIndeterminate(false);
            pDialog.setMax(100);
            pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            pDialog.setCancelable(true);
            pDialog.show();
            return pDialog;
        default:
            return null;
        }
    }

    /**
     * Background Async Task to download file
     * */
    class DownloadFileFromURL extends AsyncTask<String, String, String> {

        /**
         * Before starting background thread Show Progress Bar Dialog
         * */
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            showDialog(progress_bar_type);
        }

        /**
         * Downloading file in background thread
         * */
        @Override
        protected String doInBackground(String... f_url) {
            int count;
            try {
                URL url = new URL(f_url[0]);
                URLConnection connection = url.openConnection();
                connection.connect();

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

                // download the file
                InputStream input = new BufferedInputStream(url.openStream(),
                        8192);

                // Output stream
                OutputStream output = new FileOutputStream(Environment
                        .getExternalStorageDirectory().toString()
                        + "/2011.kml");

                byte data[] = new byte[1024];

                long total = 0;

                while ((count = input.read(data)) != -1) {
                    total += count;
                    // publishing the progress....
                    // After this onProgressUpdate will be called
                    publishProgress("" + (int) ((total * 100) / lenghtOfFile));

                    // writing data to file
                    output.write(data, 0, count);
                }

                // flushing output
                output.flush();

                // closing streams
                output.close();
                input.close();

            } catch (Exception e) {
                Log.e("Error: ", e.getMessage());
            }

            return null;
        }

        /**
         * Updating progress bar
         * */
        protected void onProgressUpdate(String... progress) {
            // setting progress percentage
            pDialog.setProgress(Integer.parseInt(progress[0]));
        }

        /**
         * After completing background task Dismiss the progress dialog
         * **/
        @Override
        protected void onPostExecute(String file_url) {
            // dismiss the dialog after the file was downloaded
            dismissDialog(progress_bar_type);

        }

    }
}

if not working in 4.0 then add:

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);

User · Answer

You should use an AsyncTask  or other way to perform a network operation on background     Override protected void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       setContentView R layout activity main          create and execute the download task     MyAsyncTask async   new MyAsyncTask        async execute        private class MyAsyncTask extends AsyncTask lt Void  Void  Void gt          execute on background  out of the UI thread      protected Long doInBackground URL    urls            DownloadFiles               More info about AsyncTask on Android documentation  Hope it helps

User · Answer

Here is the code help you to download file from server at the same time you can see the progress of downloading on your status bar   See the functionality in below image of my code       STEP - 1   Create on DownloadFileFromURL java class file to download file content from server  Here i  create an asynchronous task to download file   public class DownloadFileFromURL extends AsyncTask lt String  Integer  String gt     private NotificationManager mNotifyManager  private NotificationCompat Builder build  private File fileurl  int id   123  OutputStream output  private Context context  private String selectedDate  private String ts        public DownloadFileFromURL Context context  String selectedDate        this context   context      this selectedDate   selectedDate      protected void onPreExecute         super onPreExecute         mNotifyManager    NotificationManager  context getSystemService Context NOTIFICATION SERVICE       build   new NotificationCompat Builder context       build setContentTitle  Download                setContentText  Download in progress                setChannelId id                    setAutoCancel false               setDefaults 0               setSmallIcon R drawable ic menu download           Since android Oreo notification channel is needed      if  Build VERSION SDK INT  gt   Build VERSION CODES O            NotificationChannel channel   new NotificationChannel id                        Social Media Downloader                   NotificationManager IMPORTANCE HIGH           channel setDescription  no sound            channel setSound null  null           channel enableLights false           channel setLightColor Color BLUE           channel enableVibration false           mNotifyManager createNotificationChannel channel              build setProgress 100  0  false       mNotifyManager notify id  build build         String msg    Download started         CustomToast showToast context msg       Override protected String doInBackground String    f url        int count      ts   selectedDate split  T   0       try           URL url   new URL f url 0            URLConnection conection   url openConnection            conection connect            int lenghtOfFile   conection getContentLength             InputStream input   new BufferedInputStream url openStream                    8192              Output stream         output   new FileOutputStream Environment                  getExternalStorageDirectory   toString                     Const DownloadPath   ts     pdf            fileurl   new File Environment getExternalStorageDirectory                     Const DownloadPath   ts     pdf            byte   data   new byte 1024            long total   0           while   count   input read data      -1                total    count              int cur    int    total   100    lenghtOfFile                publishProgress Math min cur  100                if  Math min cur  100   gt  98                    try                       Thread sleep 500                     catch  InterruptedException e                        Log d  Failure    sleeping failure                                                Log i  currentProgress    currentProgress      Math min cur  100      n     cur                output write data  0  count                      output flush             output close            input close           catch  Exception e            Log e  Error     e getMessage                return null     protected void onProgressUpdate Integer    progress        build setProgress 100  progress 0   false       mNotifyManager notify id  build build         super onProgressUpdate progress       Override protected void onPostExecute String file url        build setContentText  Download complete        build setProgress 0  0  false       mNotifyManager notify id  build build           Note  If you want code with import package then Click Here   Now Step 2  You need to call above ayncronous task on your click event  for example i have set on pdf image icon   To call AsyncTask use below code    new DownloadFileFromURL fContext filename  execute serverFileUrl     Note  Here You can see filename variable in file parameter  This is the name which i use to save  my downloaded file in local device  currently i am downloading only pdf file but you can use you url in serverFileUrl parameter

User · Answer

Run these codes in thread or AsyncTask  In order to avoid duplicated callings of same  url one time for getContentLength    one time of openStream     use IOUtils toByteArray of Apache   void downloadFile String  url  String  name        try           URL u   new URL  url           DataInputStream stream   new DataInputStream u openStream             byte   buffer   IOUtils toByteArray stream           FileOutputStream fos   mContext openFileOutput  name  Context MODE PRIVATE           fos write buffer           fos flush            fos close          catch  FileNotFoundException e            e printStackTrace            return        catch  IOException e            e printStackTrace            return

User · Answer

use AsyncTask and  put your download file code in doinbackground of it    android don t allow anymore to do heavy tasks on main thread to avoid ANR Application not responding  error

User · Answer

Download File Usind Download Manager      DownloadManager downloadmanager    DownloadManager  getSystemService Context DOWNLOAD SERVICE       Uri uri   Uri parse  https   www globalgreyebooks com content books ebooks game-of-life pdf         DownloadManager Request request   new DownloadManager Request uri       request setTitle  My File        request setDescription  Downloading     request setNotificationVisibility DownloadManager Request VISIBILITY VISIBLE NOTIFY COMPLETED       request setDestinationInExternalPublicDir Environment DIRECTORY DOWNLOADS  game-of-life        downloadmanager enqueue request

User · Answer

It is bad practice to perform network operations on the main thread, which is why you are seeing the NetworkOnMainThreadException. It is prevented by the policy. If you really must do it for testing, put the following in your OnCreate:

 StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
 StrictMode.setThreadPolicy(policy);

Please remember that is is very bad practice to do this, and should ideally move your network code to an AsyncTask or a Thread.

User · Answer

Mr Iam4fun your code answer here  You will use thread        findViewById R id download  setOnClickListener new View OnClickListener              Override         public void onClick View v                 new Thread new Runnable                     public void run                         DownloadFiles                                     start      And then     public void DownloadFiles             try               URL u   new URL  http   www qwikisoft com demo ashade 20001 kml                InputStream is   u openStream                 DataInputStream dis   new DataInputStream is                byte   buffer   new byte 1024               int length               FileOutputStream fos   new FileOutputStream new File Environment getExternalStorageDirectory            data test kml                 while   length   dis read buffer   gt 0                  fos write buffer  0  length                              catch  MalformedURLException mue                Log e  SYNC getUpdate    malformed url error   mue               catch  IOException ioe                Log e  SYNC getUpdate    io error   ioe               catch  SecurityException se                Log e  SYNC getUpdate    security error   se                     Sure  it will be working

User · Answer

Apart from using AsyncTask you can put the operation in runnable-  Runnable r new Runnable      public void run        -------network operation code         --------call r in this way-- Thread t new Thread r   enter code here  t start     Also put the UI work in a haldler  such as updating a textview etc

User · Answer

Starting from api level 11 or Honeycomb doing network operations on main thread is forbidden  Use thread or asynctask  For more info visit https   developer android com reference android os NetworkOnMainThreadException html

User · Answer

I would recommend using Android DownloadManager  DownloadManager downloadmanager    DownloadManager  getSystemService Context DOWNLOAD SERVICE   Uri uri   Uri parse  http   www example com myfile mp3     DownloadManager Request request   new DownloadManager Request uri   request setTitle  My File    request setDescription  Downloading    request setNotificationVisibility DownloadManager Request VISIBILITY VISIBLE NOTIFY COMPLETED   request setVisibleInDownloadsUi false   request setDestinationUri Uri parse  file       folderName     myfile mp3      downloadmanager enqueue request

User · Answer

Simple kotlin version fun download link  String  path  String        URL link  openStream   use   input - gt          FileOutputStream File path   use   output - gt              input copyTo output                     EDIT or as extension fun String saveTo path  String        URL this  openStream   use   input - gt          FileOutputStream File path   use   output - gt              input copyTo output                              quot http   example site document quot  saveTo  quot some path file quot

[android] Android - How to download a file from a webserver

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