Using AudioManager you can control the volume of media player.
AudioManager audioManager = (AudioManager)getSystemService(Context.AUDIO_SERVICE); audioManager.setStreamVolume(AudioManager.STREAM_MUSIC, 20, 0);
also from MediaPlayer (But I didn't try that)
public void setVolume (float leftVolume, float rightVolume)
Since: API Level 1
Sets the volume on this player. This API is recommended for balancing the output of audio streams within an application. Unless you are writing an application to control user settings, this API should be used in preference to setStreamVolume(int, int, int) which sets the volume of ALL streams of a particular type. Note that the passed volume values are raw scalars. UI controls should be scaled logarithmically.
Parameters
leftVolume left volume scalar
rightVolume right volume scalar
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Using **AudioManager**, you can simply control the volume of media players.
AudioManager audioManager = (AudioManager)getSystemService(Context.AUDIO_SERVICE); audioManager.setStreamVolume(AudioManager.STREAM_MUSIC, 20, 0);
also from MediaPlayer (But I didn't try that)

setVolume(float leftVolume, float rightVolume)
> **Since: API Level 1** > > Sets the volume on this player. This API is recommended for balancing > the output of audio streams within an application. Unless you are > writing an application to control user settings, this API should be > used in preference to setStreamVolume(int, int, int) which sets the > volume of ALL streams of a particular type. Note that the passed > volume values are raw scalars. UI controls should be scaled > logarithmically. > > **Parameters** > > > leftVolume left volume scalar > > rightVolume right volume scalar