NullPointerException lors de l'ajout de lignes

Question

Je suis novice dans la programmation Android, donc j'ai du mal à ajouter dynamiquement des lignes à TableLayout. S'il vous plaît, voir un code ci-dessous:

public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
    TableLayout layout = (TableLayout) findViewById(R.layout.main); 
    Game game = new Game(); 
    Square[][] field = game.getField(); 
    int ii = 0; 
    for (Square[] sq : field) { 
     TableRow row = new TableRow(this); 
     row.setId(100 + ii); 
     for (Square square : sq) { 
      ii++; 
      Button button = new Button(this); 
      String str = "button" + Integer.toString(ii); 

      CharSequence text = str; 
      button.setId(ii); 
      button.setText(text); 
      row.addView(button, new TableRow.LayoutParams(TableRow.LayoutParams.FILL_PARENT, 
        TableRow.LayoutParams.WRAP_CONTENT)); 
     } 
     layout.addView(row, new TableLayout.LayoutParams(TableLayout.LayoutParams.FILL_PARENT, 
       TableLayout.LayoutParams.WRAP_CONTENT)); 
    } 
} 

journal:

11-29 14:54:40.939: DEBUG/AndroidRuntime(337): --- registering native functions --- 
11-29 14:54:41.669: INFO/ActivityManager(59): Starting activity: Intent { flg=0x10000000 cmp=com.example/.KrestikinolikiActivity } 
11-29 14:54:41.809: DEBUG/AndroidRuntime(337): Shutting down VM 
11-29 14:54:41.839: DEBUG/dalvikvm(337): Debugger has detached; object registry had 1 entries 
11-29 14:54:41.879: INFO/ActivityManager(59): Start proc com.example for activity com.example/.KrestikinolikiActivity: pid=344 uid=10031 gids={1015} 
11-29 14:54:41.919: INFO/AndroidRuntime(337): NOTE: attach of thread 'Binder Thread #3' failed 
11-29 14:54:42.729: ERROR/dalvikvm(344): Could not find class 'sun.reflect.generics.reflectiveObjects.NotImplementedException', referenced from method com.example.Game.getCurrentActivePlayer 
11-29 14:54:42.729: WARN/dalvikvm(344): VFY: unable to resolve new-instance 30 (Lsun/reflect/generics/reflectiveObjects/NotImplementedException;) in Lcom/example/Game; 
11-29 14:54:42.739: DEBUG/dalvikvm(344): VFY: replacing opcode 0x22 at 0x0000 
11-29 14:54:42.739: DEBUG/dalvikvm(344): VFY: dead code 0x0002-0005 in Lcom/example/Game;.getCurrentActivePlayer()Lcom/example/Player; 
11-29 14:54:42.759: DEBUG/AndroidRuntime(344): Shutting down VM 
11-29 14:54:42.759: WARN/dalvikvm(344): threadid=1: thread exiting with uncaught exception (group=0x4001d800) 
11-29 14:54:42.768: ERROR/AndroidRuntime(344): FATAL EXCEPTION: main 
     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example/com.example.KrestikinolikiActivity}: java.lang.NullPointerException 
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
     at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
     at android.os.Handler.dispatchMessage(Handler.java:99) 
     at android.os.Looper.loop(Looper.java:123) 
     at android.app.ActivityThread.main(ActivityThread.java:4627) 
     at java.lang.reflect.Method.invokeNative(Native Method) 
     at java.lang.reflect.Method.invoke(Method.java:521) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
     at dalvik.system.NativeStart.main(Native Method) 
     Caused by: java.lang.NullPointerException 
     at com.example.KrestikinolikiActivity.onCreate(KrestikinolikiActivity.java:41) 
     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) 
     ... 11 more 
11-29 14:54:42.789: WARN/ActivityManager(59): Force finishing activity com.example/.KrestikinolikiActivity 
11-29 14:54:43.288: WARN/ActivityManager(59): Activity pause timeout for HistoryRecord{44f993c0 com.example/.KrestikinolikiActivity} 

Ce que je fais mal?

Answer 1

Vous essayez d'obtenir la mise en page avec le mauvais ID. Supposons que vous ayez la main.xml suivante:

<LinearLayout 
      android:id="@+id/new_activity_layout" 
      android:layout_alignParentTop="true" 
      android:layout_width="fill_parent" 
      android:layout_height="wrap_content" 
      android:orientation="horizontal" 
      > 

Ainsi, dans le code que vous devez écrire:

TableLayout layout = (TableLayout) findViewById(R.id.new_activity_layout); 

En utilisant le même identifiant pour la mise en page et afficher le contenu est erroné. Le fait est que findViewById recherche l'id, passé en paramètre, dans le xml gonflé, que vous avez passé à setContentView. Mais il n'y a pas R.layout.main dans main.xml, mais il y a R.id.new_activity_layout là. Espérons, l'explication est plutôt claire.