Android 中如何監聽耳機鍵消息

在研究一個功能：Android如何通過耳機鍵來拍照/攝像，好處自不用多說了，拍照時可以防抖

那麼這引出一個問題，如何在 Camera/VideoCamera Activity中監聽耳機鍵。

耳機鍵在 android 中的定義為

/** Key code constant: Headset Hook key.
* Used to hang up calls and stop media. */
public static final int KEYCODE_HEADSETHOOK = 79;

主要用來接聽/掛斷 電話，播放/暫停音樂視頻等

監聽耳機鍵有兩種方式：

1，直接在 Activity 的 onKeyDown 或 onKeyUp 函數中添加對應的 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，注冊 BroadcastReceiver 來響應該按鍵

// 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;
}