android 볼륨 up down 방법

private int mStreamType = AudioManager.STREAM_MUSIC;

public void volumeUp() {
    AudioManager am = (AudioManager) getSystemService(Context.AUDIO_SERVICE);    int currVol = am.getStreamVolume(mStreamType);    int maxVol = am.getStreamMaxVolume(mStreamType);
    if (currVol < maxVol) {
        am.setStreamVolume(mStreamType, currVol + 1, AudioManager.FLAG_PLAY_SOUND);    }
}

public void volumeDown() {
    AudioManager am = (AudioManager) getSystemService(Context.AUDIO_SERVICE);    int currVol = am.getStreamVolume(mStreamType);    if (currVol > 0) {
        am.setStreamVolume(mStreamType, currVol - 1, AudioManager.FLAG_PLAY_SOUND);    }
}