Android监听音量变化

    private void registerVolumeChangeReceiver() {
        mSettingsContentObserver = new SettingsContentObserver(this, new Handler());
        getApplicationContext().getContentResolver().registerContentObserver(android.provider.Settings.System.CONTENT_URI, true, mSettingsContentObserver);
    }

    private void unregisterVolumeChangeReceiver(){
        getApplicationContext().getContentResolver().unregisterContentObserver(mSettingsContentObserver);
    }

    public class SettingsContentObserver extends ContentObserver {
        Context context;

        public SettingsContentObserver(Context c, Handler handler) {
            super(handler);
            context = c;
        }

        @Override
        public boolean deliverSelfNotifications() {
            return super.deliverSelfNotifications();
        }

        @Override
        public void onChange(boolean selfChange) {
            super.onChange(selfChange);
            AudioManager audioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
            int currentVolume = audioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
            System.out.println("currVolume:" + currentVolume);
            //TODO
        }
    }