播放默认铃声

Uri alert = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_ALARM);
mMediaPlayer = new MediaPlayer();
mMediaPlayer.setDataSource(this, alert);
final AudioManager audioManager = (AudioManager)getSystemService(Context.AUDIO_SERVICE);
if (audioManager.getStreamVolume(AudioManager.STREAM_ALARM) != 0) 
{
    player.setAudioStreamType(AudioManager.STREAM_ALARM);
    player.setLooping(true);
    player.prepare();
    player.start();
}

设置默认来电铃声