Nullpointer beim Hinzufügen von Zeilen

Question

Ich bin Neuling in Android Programmierung, so dass ich dynamisch ein Problem mit dem Hinzufügen von Zeilen zu Tablelayout habe. Bitte finden Sie einen Code unten:

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));
    }
}

log:

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}

Was tue ich falsch?

Answer 1

Sie versuchen, mit falscher ID zu bekommen Layout. Angenommen, Sie haben die folgende main.xml:

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

Also, in Code sollten Sie schreiben:

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

Mit der gleichen ID für Layout und Inhalt Ansicht ist falsch. Tatsache ist, dass findViewById Suche nach der id, in Parameter übergeben, in dem aufgeblasenen xml, Sie setContentView geben. Aber es gibt keine R.layout.main in main.xml, aber es gibt R.id.new_activity_layout dort. Hope, ist die Erklärung ziemlich klar.