android PresetReverb不起作用

Question

I am trying to add reverb effect to my mp3player,but the presetRevert does not work at all,here is the codes;
mMediaPlayer = MediaPlayer.create(this, R.raw.eason);
PresetReverb mPreReverb = new PresetReverb(1, 0);
mPreReverb.setPreset(PresetReverb.PRESET_LARGEHALL);
mMediaPlayer.attachAuxEffect(mPreReverb.getId());
mPreReverb.setEnabled(true);
mMediaPlayer.setAuxEffectSendLevel(1.0f);
mMediaPlayer.start();`

我已将权限MODIFY_AUDIO_SETTINGS添加到Manifest.xml。 请帮帮我，谢谢！