android action_media_button,为何ACTION_MEDIA_BUTTON无法处理事件？

在关于如何进行use hardware playback control keys to control audio playback的培训部分之后,我创建了一个侦听器类：

public class RemoteControlReceiver extends BroadcastReceiver {

@Override

public void onReceive(Context arg0, Intent intent) {

if (Intent.ACTION_MEDIA_BUTTON.equals(intent.getAction())) {

KeyEvent event = (KeyEvent)intent.getParcelableExtra(Intent.EXTRA_KEY_EVENT);

Log.e(TAG, "ACTION_MEDIA_BUTTON");

int keycode = event.getKeyCode();

switch (keycode)

{

case KeyEvent.KEYCODE_MEDIA_NEXT:

Log.e(TAG, "KEYCODE_MEDIA_NEXT");

break;

case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE:

Log.e(TAG, "KEYCODE_MEDIA_PLAY_PAUSE");

break;

case KeyEvent.KEYCODE_MEDIA_PREVIOUS:

Log.e(TAG, "KEYCODE_MEDIA_PREVIOUS");

break;

default:

}

if (/*KeyEvent.KEYCODE_MEDIA_PLAY*/ 126 == event.getKeyCode()) { // KEYCODE_MEDIA_PLAY undefined for API < 11

Log.e(TAG, "KEYCODE_MEDIA_PLAY");

}

}

}

}

在活动的onCreate()中注册了它：

private AudioManager mAudioManager;

private ComponentName mRemoteControlReceiver;

...

...

mAudioManager = (AudioManager)getSystemService(Context.AUDIO_SERVICE);

mRemoteControlReceiver = new ComponentName(this, RemoteControlReceiver.class);

mAudioManager.registerMediaButtonEventReceiver(mRemoteControlReceiver);

并将其注册在清单中：

但是,按下这些按钮中的任何一个都不会导致LogCat上出现任何日志消息！ (无论是否在播放我的媒体时被按下)

我的代码似乎拦截了来自其他媒体播放器的这些事件,但是为什么我看不到任何Log.e()消息？我想念什么？

顺便说一句,当我按下这些按钮中的任何一个时,将显示以下消息：

W/KeyCharacterMap(19801): Can't open keycharmap file

W/KeyCharacterMap(19801): Error loading keycharmap file '/system/usr/keychars/h2w_headset.kcm.bin'. hw.keyboards.131075.devname='h2w headset'

W/KeyCharacterMap(19801): Using default keymap: /system/usr/keychars/qwerty.kcm.bin