java - Android MediaPlayer - 位置在缓冲时跳过

Question

我在某些设备上播放音乐时遇到奇怪的行为。当音频刚开始播放时，位置会跳来跳去，播放不稳定，直到缓冲完全完成。

我从 sample code from Tutorials Point 开始.我在 OnCreate() 中这样创建 MediaPlayer:

// Create Media Player
mediaPlayer = new MediaPlayer();
mediaPlayer.setOnBufferingUpdateListener(this);
mediaPlayer.reset();
mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
prepareMediaPlayer();

prepareMediaPlayer 像这样设置数据:

private void prepareMediaPlayer() {

    try {
        mediaPlayer.setDataSource(myurl);
        mediaPlayer.prepareAsync();
        mediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
            @Override
            public void onPrepared(MediaPlayer mp) {
                Toast.makeText(getApplicationContext(), 
                        "Playing sound",Toast.LENGTH_SHORT).show();

                mediaPlayer.start();

            }
        });
    } catch (IOException e) {
        e.printStackTrace();
    }
}

和onBufferingUpdate打印缓冲进度:

@Override
public void onBufferingUpdate(MediaPlayer mediaPlayer, int bufferingProgress) {
    Log.v(TAG, "onBufferingUpdate() "+bufferingProgress + 
            "\ncurrentposition: "+mediaPlayer.getCurrentPosition());

    seekbar.setSecondaryProgress(bufferingProgress);
}

我得到的日志输出显示了媒体播放器仍在缓冲时位置如何跳跃。我已经在一些设备上进行了测试，这只发生在 Moto G 上。这是固件中的错误还是我做错了什么？

08-29 12:50:17.934 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 4
                                                                              currentposition: 0
08-29 12:50:17.934 277/com.test.mediaplayer D/MediaPlayer: setSubtitleAnchor in MediaPlayer
08-29 12:50:17.976 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 4
                                                                              currentposition: 0
08-29 12:50:18.014 27927-27945/com.test.mediaplayer V/RenderScript: 0xb7912ee8 Launching thread(s), CPUs 4
08-29 12:50:21.414 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 8
                                                                              currentposition: 7
08-29 12:50:34.930 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 11
                                                                              currentposition: 9
08-29 12:50:50.085 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 15
                                                                              currentposition: 4
08-29 12:51:32.991 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 19
                                                                              currentposition: 2
08-29 12:53:25.036 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 22
                                                                              currentposition: 5
08-29 12:53:51.976 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 26
                                                                              currentposition: 1
08-29 12:56:26.004 27927-27946/com.test.mediaplayer I/MediaHTTPConnection: proxyName: 0.0.0.0 0
08-29 12:56:34.651 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 30
                                                                              currentposition: 10
08-29 12:56:35.862 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 33
                                                                              currentposition: 1102
08-29 12:56:38.211 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 37
                                                                              currentposition: 4
08-29 12:56:40.097 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 41
                                                                              currentposition: 9
08-29 12:56:43.034 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 44
                                                                              currentposition: 9
08-29 12:56:45.130 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 48
                                                                              currentposition: 3
08-29 12:56:49.841 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 52
                                                                              currentposition: 8
08-29 12:56:52.500 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 55
                                                                              currentposition: 8
08-29 12:56:55.748 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 63
                                                                              currentposition: 7
08-29 12:56:57.080 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 74
                                                                              currentposition: 1223
08-29 12:56:59.072 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 81
                                                                              currentposition: 979
08-29 12:57:00.073 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 81
                                                                              currentposition: 1979
08-29 12:57:03.596 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 88
                                                                              currentposition: 5
08-29 12:57:05.862 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 92
                                                                              currentposition: 4
08-29 12:57:08.291 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 95
                                                                              currentposition: 8
08-29 12:57:13.903 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 99
                                                                              currentposition: 9
08-29 12:57:14.904 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 100
                                                                              currentposition: 668
08-29 12:57:34.261 277/com.test.mediaplayer V/audio-player: onBufferingUpdate() 100
                                                                              currentposition: 224068

Answer 1

developer docs 中有与此相关的说明:

There is a subtle but important difference between a newly constructed MediaPlayer object and the MediaPlayer object after reset() is called. It is a programming error to invoke methods such as getCurrentPosition() ... in the Idle state for both cases

它还添加了:

It is important to note that the Preparing state is a transient state, and the behavior of calling any method with side effect while a MediaPlayer object is in the Preparing state is undefined.

在 onPrepared 回调之前调用 getCurrentPosition() 似乎是不安全的。解决方案可能是在缓冲时暂停播放。