实时监听耳机拔除

当用户正在使用我们产品里提供的音乐播放器播放音乐时，用户把耳机或者蓝牙耳机接入后，过一会儿，用户又把耳机给拔除，或者断开蓝牙耳机的连接，我们需要暂停播放音乐，定义一个BroadcastReceiver对象，  对于有线耳机，监听Intent.ACTION_HEADSET_PLUG系统广播，对于蓝牙耳机，监听BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED系统广播

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private void registerHeadsetPlugReceiver() {            IntentFilter intentFilter = new IntentFilter();            intentFilter.addAction("android.intent.action.HEADSET_PLUG");            registerReceiver(headsetPlugReceiver, intentFilter);                       // for bluetooth headset connection receiver          IntentFilter bluetoothFilter = new IntentFilter(BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED);          registerReceiver(headsetPlugReceiver, bluetoothFilter);      }              private BroadcastReceiver headsetPlugReceiver = new BroadcastReceiver() {              @Override          public void onReceive(Context context, Intent intent) {                              String action = intent.getAction();              if (BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED.equals(action)) {                  BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();                  if(BluetoothProfile.STATE_DISCONNECTED == adapter.getProfileConnectionState(BluetoothProfile.HEADSET)) {                      //Bluetooth headset is now disconnected                      handleHeadsetDisconnected();                  }              } else if ("android.intent.action.HEADSET_PLUG".equals(action)) {                  if (intent.hasExtra("state")) {                      if (intent.getIntExtra("state", 0) == 0) {                          handleHeadsetDisconnected();                      }                  }              }          }                  };

 这样做可以基本满足需求，但不完美，因为当拔出有线耳机时，播放器不会马上暂停，要等上一秒钟，才会收到Android的系统广播，

android.intent.action.HEADSET_PLUG，他说其他音乐播放器没有这个延迟，经过调查发现，QQ音乐确实没有这个延迟，耳机一拔，播放器立刻暂停，

相关资料：从硬件层面来看，直接监听耳机拔出事件不难，耳机的拔出和插入，会引起手机电平的变化，然后触发什么什么中断，

最终在stack overflow找到答案，监听Android的系统广播AudioManager.ACTION_AUDIO_BECOMING_NOISY， 但是这个广播只是针对有线耳机，或者无线耳机的手机断开连接的事件，监听不到有线耳机和蓝牙耳机的接入，但对于我的需求来说足够了，监听这个广播就没有延迟了，UI可以立即响应

private void registerHeadsetPlugReceiver() {
        IntentFilter intentFilter = new IntentFilter(AudioManager.ACTION_AUDIO_BECOMING_NOISY);
        registerReceiver(headsetPlugReceiver, intentFilter);
    }

    private BroadcastReceiver headsetPlugReceiver = new BroadcastReceiver() {

        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (AudioManager.ACTION_AUDIO_BECOMING_NOISY.equals(action)) {
                handleHeadsetDisconnected();
            }
        }

    };