自定义Button，复写里面的onKeyDown，不起作用

public class MyButton extends Button
{
	public MyButton(Context context , AttributeSet set)
	{
		super(context , set);
	}
	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event)
	{
		super.onKeyDown(keyCode , event);
		Log.v("-MyButton-" , "the onKeyDown in MyButton");
		//返回false，表明并未完全处理该事件，该事件依然向外扩散
		return false;
	}
}

public class Propagation extends Activity
{
	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		MyButton bn = (MyButton)findViewById(R.id.bn);
		//bn.setFocusable(true); 
		bn.requestFocus();
        bn.setFocusableInTouchMode(true);
		//为bn绑定事件监听器
		bn.setOnKeyListener(new OnKeyListener()
		{
			@Override
			public boolean onKey(View source
				, int keyCode, KeyEvent event)
			{
				//只处理按下键的事件
				if (event.getAction() == KeyEvent.ACTION_DOWN)
				{
					Log.v("-Listener-" , "the onKeyDown in Listener");
				}
				// 返回false，表明该事件会向外传播
				return false;
			}
		});
	}
	//重写onKeyDown方法，该方法可监听它所包含的所有组件的按键被按下事件
	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event)
	{
		super.onKeyDown(keyCode , event);
		Log.v("-Activity-" , "the onKeyDown in Activity");
		//返回false，表明并未完全处理该事件，该事件依然向外扩散
		return false;
	}
}