在研究一个功能：Android如何通过耳机键来拍照/摄像，好处自不用多说了，拍照时可以防抖

那么这引出一个问题，如何在 Camera/VideoCamera Activity中监听耳机键。

耳机键在 android 中的定义为

/** Key code constant: Headset Hook key.

* Used to hang up calls and stop media. */

public static final int KEYCODE_HEADSETHOOK    = 79;

主要用来接听/挂断 电话，播放/暂停音乐视频等

监听耳机键有两种方式：

1，直接在 Activity 的 onKeyDown 或 onKeyUp 函数中添加对应的 case 即可

@Override

public boolean onKeyUp(int keyCode, KeyEvent event) {

switch (keyCode) {

……

case KeyEvent.KEYCODE_HEADSETHOOK:

//add your code here

……

}

return super.onKeyUp(keyCode, event);

}

2，注册 BroadcastReceiver 来响应该按键

//  listener media button

private BroadcastReceiver mMediaButtonReceiver = null;

private class MediaButtonBroadcastReceiver extends BroadcastReceiver {

@Override

public void onReceive(Context context, Intent intent) {

Log.v(TAG," call MediaButtonBroadcastReceiver");

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

Log.v(TAG, " event "+event);

if ((event != null)&& (event.getKeyCode() == KeyEvent.KEYCODE_HEADSETHOOK)) {

Toast.makeText(VideoCamera.this, R.string.hook, Toast.LENGTH_SHORT).show();

}

}

}

//registerReceiver

IntentFilter mediaButtonIntentFilter = new IntentFilter();

mediaButtonIntentFilter.addAction(Intent.ACTION_MEDIA_BUTTON);

mMediaButtonReceiver = new MediaButtonBroadcastReceiver();

registerReceiver(mMediaButtonReceiver, mediaButtonIntentFilter);

//unregisterReceiver

if (mMediaButtonReceiver != null){

unregisterReceiver(mMediaButtonReceiver);

mMediaButtonReceiver = null;

}