Android BroadCastReceiver for volume key up and down

问题

If a user presses volume key up or down is it possible to detect it in my broadcast receiver? I need the full code.

Here is my Intent filter

IntentFilter filter = new IntentFilter();
filter.addAction("android.media.VOLUME_CHANGED_ACTION");

and my onReceive method is

public void onReceive(Context arg0, Intent intent) {
      KeyEvent ke = (KeyEvent)intent.getExtras().get(Intent.EXTRA_KEY_EVENT);
        if (ke .getKeyCode() == KeyEvent.KEYCODE_VOLUME_UP) {
                System.out.println("I got volume up event");
         }else if (ke .getKeyCode() == KeyEvent.KEYCODE_VOLUME_DOWN) {
                System.out.println("I got volume key down event");
         }
    }

It gives me a null KeyEvent... any idea?

回答1:

The intent does not have an EXTRA_KEY_EVENT extra. It does have an extra android.media.EXTRA_VOLUME_STREAM_VALUE which contains the new volume.

int volume = (Integer)intent.getExtras().get("android.media.EXTRA_VOLUME_STREAM_VALUE");

If you store the old value, you can infer whether volume up or down was pressed.

来源：https://stackoverflow.com/questions/12561142/android-broadcastreceiver-for-volume-key-up-and-down