How to adjust AudioManager Volume level Android

 This should work

AudioManager audio = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
int currentVolume = audio.getStreamVolume(AudioManager.STREAM_MUSIC);
int maxVolume = audio.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
float percent = 0.7f;
int seventyVolume = (int) (maxVolume*percent);
audio.setStreamVolume(AudioManager.STREAM_MUSIC, seventyVolume, 0);