从 url 播放时 MediaPlayer 未准备：MediaPlayer：尝试在没有有效媒体播放器的情况下调用 getDuration

Question

我正在开发一个应用程序，该应用程序使用 HTTP 连接 URL 将一部 Android 手机上的歌曲播放到另一部手机上。这是我初始化和启动 MediaPlayer 的代码：-

        Log.d(TAG, "Rohit insidePlaysong of client");
        mp.reset();
        Log.d(TAG, "Rohit Music player is reset");
        mp.setDataSource(url);
        Log.d(TAG, "Rohit Music player : data source set");

        mp.setAudioStreamType(AudioManager.STREAM_MUSIC);

        Log.d(TAG, "Rohit Music player audio stream type set");

        //mp.prepare();
        //Rohit changing the method of preparing
        mp.setOnPreparedListener(new OnPreparedListener() {

            @Override
            public void onPrepared(MediaPlayer mp) {
                // TODO Auto-generated method stub
                Log.d(TAG, "Rohit inside onPrepared, Now starting Music Player");
                mp.start();
            }
        });
        mp.prepareAsync();
        //mp.prepare();
        //Log.d(TAG, "Rohit Music player prepared");
        // TODO: make sure we have buffered REALLY
        // buffered the music, currently this is a big
        // HACK and takes a lot of time. We can do
        // better!
        /*mp.start();
        mp.pause();
        mp.start();
        mp.pause();
        mp.start();
        mp.pause();
        mp.start();
        mp.pause();
        mp.start();
        mp.pause();*/

        Log.d(TAG, "Rohit Music player started");

        musicTimer = mActivity.retrieveTimer();

        Log.d(TAG, "Rohit retrieved timer");

        // let the music timer determine when to play the future playback
        musicTimer.playFutureMusic(mp, startTime, startPos);

        Log.d(TAG, "Rohit future music set to timer");

        // Changing Button Image to pause image
        // btnPlay.setImageResource(R.drawable.btn_pause);

        // set Progress bar values
        songProgressBar.setProgress(0);
        songProgressBar.setMax(100);

        // Updating progress bar
        updateProgressBar();
        // parsing songTitle

        Log.d(TAG, "Rohit updated song progress");

这些是打印的相应日志（用“Rohit”过滤）：-

12-19 19:25:42.827   463   463 D Speaker Music Player: Rohit insidePlaysong of client
12-19 19:25:42.827   463   463 D Speaker Music Player: Rohit Music player is reset
12-19 19:25:42.847   463   463 D Speaker Music Player: Rohit Music player : data source set
12-19 19:25:42.847   463   463 D Speaker Music Player: Rohit Music player audio stream type set
12-19 19:25:42.857   463   463 D Speaker Music Player: Rohit Music player started
12-19 19:25:42.857   463   463 D Speaker Music Player: Rohit retrieved timer
12-19 19:25:42.857   463   463 D Speaker Music Player: Rohit future music set to timer
12-19 19:25:42.857   463   463 D Speaker Music Player: Rohit updated song progress

如您所见，“Rohit inside onPrepared，现在正在启动音乐播放器”从未准备好。

虽然从 url 我可以看到 MediaPlayer 能够正确获取 songName，但是在我的代码中使用 mp.getDuration() 时，我的日志中出现以下错误：-

12-19 19:25:42.857   463   463 V MediaPlayer: getDuration_l<br>
12-19 19:25:42.857   463   463 E MediaPlayer: Attempt to call getDuration without a valid mediaplayer
12-19 19:25:42.857   463   463 V MediaPlayer: message received msg=100, ext1=-38, ext2=0
12-19 19:25:42.857  3237  1397 V GenericSource: [Flag] set 0x8 -> mFlags = 0x8
12-19 19:25:42.857  3237  1398 V GenericSource: onPrepareAsync<br>
12-19 19:25:42.857  6089  6096 I art     : Ignoring second debugger -- accepting and dropping
12-19 19:25:42.857   463   463 E MediaPlayer: error (-38, 0)<br>
12-19 19:25:42.857   463   463 V MediaPlayer: callback application
12-19 19:25:42.857  3438  3502 V BroadcastQueue: [background] Process cur broadcast BroadcastRecord{62bf8b6 u0 com.samsung.android.providers.context.log.action.USE_APP_FEATURE_SURVEY qIdx=4}, state= (APP_RECEIVE) DELIVERED for app ProcessRecord{98bbb0 6103:com.samsung.android.providers.context/u0a8}
12-19 19:25:42.857   463   463 V MediaPlayer: back from callback
12-19 19:25:42.857   463   463 V MediaPlayer-JNI: getDuration: 0 (msec)

谁能帮我知道，MediaPlayer 无法准备的可能原因是什么？

Answer 1

您正在尝试获得持续时间，而无需等待MediaPlayer 准备。在准备好之前，您不必使用MediaPlayer。所以prepareAsync下面的代码必须在prepareListener回调中调用：

mp.reset();
mp.setDataSource(url);
mp.setAudioStreamType(AudioManager.STREAM_MUSIC);
mp.setOnPreparedListener(new OnPreparedListener() {
    @Override
    public void onPrepared(MediaPlayer mp) {
        mp.start();
        //any further actions on mediaPlayer here
    }
});
mp.prepareAsync();