如何将自定义视图插入XML的LinearLayout

example

<?xml version=\"1.0\" encoding=\"utf-8\"?>
<LinearLayout
  xmlns:android=\"http://schemas.android.com/apk/res/android\"
  xmlns:app=\"http://schemas.android.com/apk/res/jembalang.comfest.game\"
  android:layout_width=\"fill_parent\"
  android:layout_height=\"fill_parent\">
  <jembalang.compfest.game.GameThread
    android:id=\"@+id/game_view\"
    android:layout_width=\"fill_parent\"
    android:layout_height=\"fill_parent\">
  </jembalang.compfest.game.GameThread>
  <Button 
    android:text=\"Button\" 
    android:id=\"@+id/button1\" 
    android:layout_width=\"wrap_content\" 
    android:layout_height=\"wrap_content\">
  </Button>
</LinearLayout>

setContentView(R.layout.cobagabung);
gameView = (GameThread) Jembalang.this.findViewById(R.id.game_view);
gameView.setFocusable(true);
gameView.setFocusableInTouchMode(
gameView.start();

public class GameThread extends View implements Runnable,OnKeyListener{
    public GameThread(Context context,AttributeSet attr){
        super(context, attr);
        ...
    }
    public GameThread(Context context) {
        super(context);
        ...
    }

findViewById

null

CustomView

GameThread