Android app unable to start activity componentinfo

Question

I m a new Android programmer and recently  a lot of my projects have been getting this error   07-31 23 45 19 592  ERROR AndroidRuntime 716   java lang RuntimeException  Unable to start       activity ComponentInfo com amrit musifind com amrit musifind Main     java lang NullPointerException   Can anyone help me solve this problem   Here s the entire logcat stack trace   07-31 23 45 18 512  INFO ActivityManager 63   Starting activity  Intent        act android intent action MAIN cat  android intent category LAUNCHER  flg 0x10200000    cmp com amrit musifind  Main   07-31 23 45 18 682  INFO ActivityManager 63   Start proc com amrit musifind for activity    com amrit musifind  Main  pid 716 uid 10025 gids  3003  07-31 23 45 18 962  INFO jdwp 716   received file descriptor 20 from ADB 07-31 23 45 19 102  DEBUG ddm-heap 716   Got feature list request 07-31 23 45 19 572  DEBUG AndroidRuntime 716   Shutting down VM 07-31 23 45 19 572  WARN dalvikvm 716   threadid 3  thread exiting with uncaught    exception  group 0x4001aa28  07-31 23 45 19 572  ERROR AndroidRuntime 716   Uncaught handler  thread main exiting due  to uncaught exception 07-31 23 45 19 592  ERROR AndroidRuntime 716   java lang RuntimeException  Unable to     start activity ComponentInfo com amrit musifind com amrit musifind Main       java lang NullPointerException 07-31 23 45 19 592  ERROR AndroidRuntime 716       at     android app ActivityThread performLaunchActivity ActivityThread java 2401  07-31 23 45 19 592  ERROR AndroidRuntime 716       at     android app ActivityThread handleLaunchActivity ActivityThread java 2417  07-31 23 45 19 592  ERROR AndroidRuntime 716       at     android app ActivityThread access 2100 ActivityThread java 116  07-31 23 45 19 592  ERROR AndroidRuntime 716       at    android app ActivityThread H handleMessage ActivityThread java 1794  07-31 23 45 19 592  ERROR AndroidRuntime 716       at    android os Handler dispatchMessage Handler java 99  07-31 23 45 19 592  ERROR AndroidRuntime 716       at        android os Looper loop Looper java 123  07-31 23 45 19 592  ERROR AndroidRuntime 716       at    android app ActivityThread main ActivityThread java 4203  07-31 23 45 19 592  ERROR AndroidRuntime 716       at     java lang reflect Method invokeNative Native Method  07-31 23 45 19 592  ERROR AndroidRuntime 716       at    java lang reflect Method invoke Method java 521  07-31 23 45 19 592  ERROR AndroidRuntime 716       at    com android internal os ZygoteInit MethodAndArgsCaller run ZygoteInit java 791  07-31 23 45 19 592  ERROR AndroidRuntime 716       at    com android internal os ZygoteInit main ZygoteInit java 549  07-31 23 45 19 592  ERROR AndroidRuntime 716       at    dalvik system NativeStart main Native Method  07-31 23 45 19 592  ERROR AndroidRuntime 716   Caused by  java lang NullPointerException 07-31 23 45 19 592  ERROR AndroidRuntime 716       at    com amrit musifind Main onCreate Main java 44  07-31 23 45 19 592  ERROR AndroidRuntime 716       at  android app Instrumentation callActivityOnCreate Instrumentation java 1123  07-31 23 45 19 592  ERROR AndroidRuntime 716       at      android app ActivityThread performLaunchActivity ActivityThread java 2364  07-31 23 45 19 592  ERROR AndroidRuntime 716           11 more 07-31 23 45 19 612  INFO Process 63   Sending signal  PID  716 SIG  3 07-31 23 45 19 612  INFO dalvikvm 716   threadid 7  reacting to signal 3 07-31 23 45 19 642  INFO dalvikvm 716   Wrote stack trace to   data anr traces txt  07-31 23 45 21 422  INFO Process 716   Sending signal  PID  716 SIG  9 07-31 23 45 21 442  INFO ActivityManager 63   Process com amrit musifind  pid 716  has    died  07-31 23 45 21 583  WARN UsageStats 63   Unexpected resume of com android launcher while     already resumed in com amrit musifind 07-31 23 45 21 712  WARN InputManagerService 63   Window already focused  ignoring focus     gain of  com android internal view IInputMethodClient Stub Proxy 439559d0 07-31 23 45 23 482  DEBUG AndroidRuntime 725    gt  gt  gt  gt  gt  gt  gt  gt  gt  gt  gt  gt  gt  gt  AndroidRuntime START      lt  lt  lt  lt  lt  lt  lt  lt  lt  lt  lt  lt  lt  lt  07-31 23 45 23 482  DEBUG AndroidRuntime 725   CheckJNI is ON 07-31 23 45 23 812  DEBUG AndroidRuntime 725   --- registering native functions --- 07-31 23 45 23 832  INFO jdwp 725   received file descriptor 20 from ADB 07-31 23 45 24 193  DEBUG ddm-heap 725   Got feature list request 07-31 23 45 25 052  DEBUG AndroidRuntime 725   Shutting down VM 07-31 23 45 25 052  DEBUG dalvikvm 725   DestroyJavaVM waiting for non-daemon threads to    exit 07-31 23 45 25 062  DEBUG dalvikvm 725   DestroyJavaVM shutting VM down 07-31 23 45 25 062  DEBUG dalvikvm 725   HeapWorker thread shutting down 07-31 23 45 25 062  DEBUG dalvikvm 725   HeapWorker thread has shut down 07-31 23 45 25 073  DEBUG jdwp 725   JDWP shutting down net    07-31 23 45 25 073  DEBUG jdwp 725       peer disconnected 07-31 23 45 25 073  INFO dalvikvm 725   Debugger has detached  object registry had 1    entries 07-31 23 45 25 093  DEBUG dalvikvm 725   VM cleaning up 07-31 23 45 25 113  DEBUG dalvikvm 725   LinearAlloc 0x0 used 665652 of 4194304  15   07-31 23 47 22 712  DEBUG dalvikvm 104   GC freed 9173 objects   524184 bytes in 149ms   Heres the 1st activity  start java  package com amrit musifind   import java io BufferedReader  import java io InputStreamReader   import org apache http HttpResponse  import org apache http client HttpClient  import org apache http client methods HttpGet  import org apache http impl client DefaultHttpClient   import com amrit musifind R   import android app ListActivity  import android content Intent  import android os Bundle  import android util Log  import android view View  import android widget AdapterView  import android widget AdapterView OnItemClickListener  import android widget ListAdapter  import android widget ListView  import android widget SimpleAdapter  import android widget Toast  import android app Activity  import android os Bundle  import android view View  import android view View OnClickListener  import android widget Button  import android widget EditText  import android widget TextView   public abstract class start extends Activity implements OnClickListener    Button buttonGo  buttonReset  EditText EditTextinput  String input       String ur    http   www tastekid com ask ws q    String l     amp f musifin2125 amp k mjjlnzkyzwuz amp format JSON   String url             Called when the activity is first created      Override public void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       setContentView R layout main        buttonGo    Button  findViewById R id buttonGo       buttonReset    Button  findViewById R id buttonReset        EditTextinput    EditText  findViewById R id EditTextinput          Button listener     buttonReset setOnClickListener this       buttonGo setOnClickListener this      public void onClick  View src       switch src getId             case R id buttonGo              input   EditTextinput getText   toString                url   ur   input   l                 Intent Main   new Intent this  ToClass class               Main putExtra  userurl   url               startActivity Main               break           case R id buttonReset              EditTextinput setText                  break                      The second activity  Main java  package com amrit musifind   import java util ArrayList  import java util HashMap   import org json JSONArray  import org json JSONException  import org json JSONObject  import org w3c dom Document  import org w3c dom Element  import org w3c dom NodeList   import com amrit musifind JSONfunctions  import com amrit musifind R   import android app ListActivity  import android content Intent  import android os Bundle  import android util Log  import android view View  import android widget AdapterView  import android widget AdapterView OnItemClickListener  import android widget ListAdapter  import android widget ListView  import android widget SimpleAdapter  import android widget Toast  import android app Activity  import android os Bundle  import android view View  import android view View OnClickListener  import android widget Button  import android widget EditText  import android widget TextView   public class Main extends ListActivity       Called when the activity is first created      Override public void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       setContentView R layout listplaceholder        Intent intent   getIntent        String url   intent getExtras   getString  userurl         ArrayList lt HashMap lt String  String gt  gt  mylist   new ArrayList lt HashMap lt String  String gt  gt                   JSONObject json   JSONfunctions getJSONfromURL url        try          JSONObject earthquakes   json getJSONObject  Similar            JSONArray info   earthquakes getJSONArray  Results             for  int i   0  i  lt  info length    i                  HashMap lt String  String gt  map   new HashMap lt String  String gt                 JSONObject e   info getJSONObject i                map put  id   String valueOf i                map put  name    Name     e getString  Name                 map put  type    Type      e getString  Type                 mylist add map                      JSONArray  results   json getJSONArray  Results             for int i 0 i lt results length   i                                         HashMap lt String  String gt  map   new HashMap lt String  String gt                     JSONObject e   results getJSONObject i                map put  id    String valueOf i                map put  name    Name     e getString  name                 map put  type    Type       e getString  type                 mylist add map                                      catch JSONException e             Log e  log tag    Error parsing data   e toString                ListAdapter adapter   new SimpleAdapter this  mylist   R layout main            new String      name    type               new int     R id item title  R id item subtitle          setListAdapter adapter        final ListView lv   getListView        lv setTextFilterEnabled true         lv setOnItemClickListener new OnItemClickListener             public void onItemClick AdapterView lt   gt  parent  View view  int position  long id                               SuppressWarnings  unchecked               HashMap lt String  String gt  o    HashMap lt String  String gt   lv getItemAtPosition position                                  Toast makeText Main this   ID      o get  id        was clicked                     Toast LENGTH SHORT  show                                         Lastly  my manifest file  AndroidManifest xml   lt  xml version  1 0  encoding  utf-8   gt   lt manifest xmlns android  http   schemas android com apk res android      package  com amrit musifind      android versionCode  1      android versionName  1 0  gt       lt uses-sdk android minSdkVersion  4    gt        lt application android icon   drawable icon  android label   string app name  gt           lt activity android name   start  android label   string app name  gt               lt intent-filter gt                   lt action android name  android intent action start    gt                   lt category android name  android intent category LAUNCHER    gt               lt  intent-filter gt           lt  activity gt           lt activity android name    Main  gt               lt intent-filter gt                   lt action android name  android intent action Main    gt               lt  intent-filter gt           lt  activity gt       lt  application gt        lt uses-permission android name  android permission INTERNET    gt    lt  manifest gt    Any help is much appreciated  without solving this problem I can t test my app out

User · Accepted Answer

Your null pointer exception seems to be on this line:

String url = intent.getExtras().getString("userurl");

because intent.getExtras() returns null when the intent doesn't have any extras.

You have to realize that this piece of code:

Intent Main = new Intent(this, ToClass.class);
Main.putExtra("userurl", url);
startActivity(Main);

doesn't start the activity you wrote in Main.java, it will attempt to start an activity called ToClass and if that doesn't exist, your app crashes.

Also, there is no such thing as "android.intent.action.start" so the manifest should look more like:

<activity android:name=".start" android:label="@string/app_name">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>
<activity android:name= ".Main">
</activity>

I hope this fixes some of the issues you are encountering but I strongly suggest you check out some "getting started" tutorials for android development and build up from there.

User · Answer

The question is answered already  but I want add more information about the causes      Android app unable to start activity componentinfo   This error often comes with appropriate logs  You can read logs and can solve this issue easily   Here is a sample log  In which you can see clearly ClassCastException  So this issue came because TextView cannot be cast to EditText      Caused by  java lang ClassCastException  android widget TextView   cannot be cast to android widget EditText   11-04 01 24 10 403  D AndroidRuntime 1050   Shutting down VM 11-04 01 24 10 403  W dalvikvm 1050   threadid 1  thread exiting with uncaught exception  group 0x41465700  11-04 01 24 10 543  E AndroidRuntime 1050   FATAL EXCEPTION  main 11-04 01 24 10 543  E AndroidRuntime 1050   java lang RuntimeException  Unable to start activity ComponentInfo com troysantry tipcalculator com troysantry tipcalculator TipCalc   java lang ClassCastException  android widget TextView cannot be cast to android widget EditText 11-04 01 24 10 543  E AndroidRuntime 1050       at android app ActivityThread performLaunchActivity ActivityThread java 2211  11-04 01 24 10 543  E AndroidRuntime 1050       at android app ActivityThread handleLaunchActivity ActivityThread java 2261  11-04 01 24 10 543  E AndroidRuntime 1050       at android app ActivityThread access 600 ActivityThread java 141  11-04 01 24 10 543  E AndroidRuntime 1050       at android app ActivityThread H handleMessage ActivityThread java 1256  11-04 01 24 10 543  E AndroidRuntime 1050       at android os Handler dispatchMessage Handler java 99  11-04 01 24 10 543  E AndroidRuntime 1050       at android os Looper loop Looper java 137  11-04 01 24 10 543  E AndroidRuntime 1050       at android app ActivityThread main ActivityThread java 5103  11-04 01 24 10 543  E AndroidRuntime 1050       at java lang reflect Method invokeNative Native Method  11-04 01 24 10 543  E AndroidRuntime 1050       at java lang reflect Method invoke Method java 525  11-04 01 24 10 543  E AndroidRuntime 1050       at com android internal os ZygoteInit MethodAndArgsCaller run ZygoteInit java 737  11-04 01 24 10 543  E AndroidRuntime 1050       at com android internal os ZygoteInit main ZygoteInit java 553  11-04 01 24 10 543  E AndroidRuntime 1050       at dalvik system NativeStart main Native Method  11-04 01 24 10 543  E AndroidRuntime 1050   Caused by  java lang ClassCastException  android widget TextView cannot be cast to android widget EditText 11-04 01 24 10 543  E AndroidRuntime 1050       at com troysantry tipcalculator TipCalc onCreate TipCalc java 45  11-04 01 24 10 543  E AndroidRuntime 1050       at android app Activity performCreate Activity java 5133  11-04 01 24 10 543  E AndroidRuntime 1050       at android app Instrumentation callActivityOnCreate Instrumentation java 1087  11-04 01 24 10 543  E AndroidRuntime 1050       at android app ActivityThread performLaunchActivity ActivityThread java 2175  11-04 01 24 10 543  E AndroidRuntime 1050           11 more 11-04 01 29 11 177  I Process 1050   Sending signal  PID  1050 SIG  9 11-04 01 31 32 080  D AndroidRuntime 1109   Shutting down VM 11-04 01 31 32 080  W dalvikvm 1109   threadid 1  thread exiting with uncaught exception  group 0x41465700  11-04 01 31 32 194  E AndroidRuntime 1109   FATAL EXCEPTION  main 11-04 01 31 32 194  E AndroidRuntime 1109   java lang RuntimeException  Unable to start activity ComponentInfo com troysantry tipcalculator com troysantry tipcalculator TipCalc   java lang ClassCastException  android widget TextView cannot be cast to android widget EditText 11-04 01 31 32 194  E AndroidRuntime 1109       at android app ActivityThread performLaunchActivity ActivityThread java 2211  11-04 01 31 32 194  E AndroidRuntime 1109       at android app ActivityThread handleLaunchActivity ActivityThread java 2261  11-04 01 31 32 194  E AndroidRuntime 1109       at android app ActivityThread access 600 ActivityThread java 141  11-04 01 31 32 194  E AndroidRuntime 1109       at android app ActivityThread H handleMessage ActivityThread java 1256  11-04 01 31 32 194  E AndroidRuntime 1109       at android os Handler dispatchMessage Handler java 99  11-04 01 31 32 194  E AndroidRuntime 1109       at android os Looper loop Looper java 137  11-04 01 31 32 194  E AndroidRuntime 1109       at android app ActivityThread main ActivityThread java 5103  11-04 01 31 32 194  E AndroidRuntime 1109       at java lang reflect Method invokeNative Native Method  11-04 01 31 32 194  E AndroidRuntime 1109       at java lang reflect Method invoke Method java 525  11-04 01 31 32 194  E AndroidRuntime 1109       at com android internal os ZygoteInit MethodAndArgsCaller run ZygoteInit java 737  11-04 01 31 32 194  E AndroidRuntime 1109       at com android internal os ZygoteInit main ZygoteInit java 553  11-04 01 31 32 194  E AndroidRuntime 1109       at dalvik system NativeStart main Native Method  11-04 01 31 32 194  E AndroidRuntime 1109   Caused by  java lang ClassCastException  android widget TextView cannot be cast to android widget EditText 11-04 01 31 32 194  E AndroidRuntime 1109       at com troysantry tipcalculator TipCalc onCreate TipCalc java 44  11-04 01 31 32 194  E AndroidRuntime 1109       at android app Activity performCreate Activity java 5133  11-04 01 31 32 194  E AndroidRuntime 1109       at android app Instrumentation callActivityOnCreate Instrumentation java 1087  11-04 01 31 32 194  E AndroidRuntime 1109       at android app ActivityThread performLaunchActivity ActivityThread java 2175  11-04 01 31 32 194  E AndroidRuntime 1109           11 more 11-04 01 36 33 195  I Process 1109   Sending signal  PID  1109 SIG  9 11-04 02 11 09 684  D AndroidRuntime 1167   Shutting down VM 11-04 02 11 09 684  W dalvikvm 1167   threadid 1  thread exiting with uncaught exception  group 0x41465700  11-04 02 11 09 855  E AndroidRuntime 1167   FATAL EXCEPTION  main 11-04 02 11 09 855  E AndroidRuntime 1167   java lang RuntimeException  Unable to start activity ComponentInfo com troysantry tipcalculator com troysantry tipcalculator TipCalc   java lang ClassCastException  android widget TextView cannot be cast to android widget EditText 11-04 02 11 09 855  E AndroidRuntime 1167       at android app ActivityThread performLaunchActivity ActivityThread java 2211  11-04 02 11 09 855  E AndroidRuntime 1167       at android app ActivityThread handleLaunchActivity ActivityThread java 2261  11-04 02 11 09 855  E AndroidRuntime 1167       at android app ActivityThread access 600 ActivityThread java 141  11-04 02 11 09 855  E AndroidRuntime 1167       at android app ActivityThread H handleMessage ActivityThread java 1256  11-04 02 11 09 855  E AndroidRuntime 1167       at android os Handler dispatchMessage Handler java 99  11-04 02 11 09 855  E AndroidRuntime 1167       at android os Looper loop Looper java 137  11-04 02 11 09 855  E AndroidRuntime 1167       at android app ActivityThread main ActivityThread java 5103  11-04 02 11 09 855  E AndroidRuntime 1167       at java lang reflect Method invokeNative Native Method  11-04 02 11 09 855  E AndroidRuntime 1167       at java lang reflect Method invoke Method java 525  11-04 02 11 09 855  E AndroidRuntime 1167       at com android internal os ZygoteInit MethodAndArgsCaller run ZygoteInit java 737  11-04 02 11 09 855  E AndroidRuntime 1167       at com android internal os ZygoteInit main ZygoteInit java 553  11-04 02 11 09 855  E AndroidRuntime 1167       at dalvik system NativeStart main Native Method  11-04 02 11 09 855  E AndroidRuntime 1167   Caused by  java lang ClassCastException  android widget TextView cannot be cast to android widget EditText 11-04 02 11 09 855  E AndroidRuntime 1167       at com troysantry tipcalculator TipCalc onCreate TipCalc java 44  11-04 02 11 09 855  E AndroidRuntime 1167       at android app Activity performCreate Activity java 5133  11-04 02 11 09 855  E AndroidRuntime 1167       at android app Instrumentation callActivityOnCreate Instrumentation java 1087  11-04 02 11 09 855  E AndroidRuntime 1167       at android app ActivityThread performLaunchActivity ActivityThread java 2175  11-04 02 11 09 855  E AndroidRuntime 1167           11 more   Some Common Mistakes   1 findViewById   of non existing view  Like when you use findViewById R id button  when button id does not exist in layout XML   2  Wrong cast   If you wrong cast some class  then you get this error  Like you cast RelativeLayout to LinearLayout or EditText to TextView    3  Activity not registered in manifest xml  If you did not register Activity in manifest xml then this error comes   4  findViewById   with declaration at top level  Below code is incorrect  This will create error  Because you should do findViewById   after calling setContentView    Because an View can be there after it is created   public class MainActivity extends Activity      ImageView mainImage    ImageView  findViewById R id imageViewMain     incorrect way     Override   protected void onCreate Bundle savedInstanceState       super onCreate savedInstanceState       setContentView R layout activity main       mainImage    ImageView  findViewById R id imageViewMain     correct way                   5  Starting abstract Activity class   When you try to start an Activity which is abstract  you will will get this error  So just remove abstract keyword before activity class name   6  Using kotlin but kotlin not configured   If your activity is written in Kotlin and you have not setup kotlin in your app  then you will get error  You can follow simple steps as written in Android Link or Kotlin Link  You can check this answer too   More information  Read about Downcast and Upcast  Read about findViewById   method of Activity class  Super keyword in Java  How to register activity in manifest

[android] Android app unable to start activity componentinfo

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