MediaPlayer创建

 // 注意用这种方式创建的Media不需要 mediaPlayer.prepare();
                // 创建的时候已经调用过了
                mMediaPlayer = MediaPlayer.create(this.mContext,
                    R.raw.voip_call_ring);

 AudioManager mAudioManager = (AudioManager) mContext.getSystemService(Context.AUDIO_SERVICE);
                mAudioManager.setSpeakerphoneOn(false);
                mMediaPlayer = new MediaPlayer();
                try
                {
                    // content://settings/system/ringtone
                    Uri alert = RingtoneManager
                        .getDefaultUri(RingtoneManager.TYPE_RINGTONE);
                    // alert = Uri
                    // .parse(VoipLogic.getInstance().getRingFilePath());
                    mMediaPlayer.setAudioStreamType(AudioManager.STREAM_RING);
                    mMediaPlayer.setDataSource(mContext,
                        alert);
                    mMediaPlayer.prepare();
                }
                catch (IOException e)
                {
                    e.printStackTrace();
                }
                break;