Android MediaPlayer重置冻结UI

Question

MediaPlayer更改dataSource播放器时我的Android有问题.根据MediaPlayer(http://developer.android.com/reference/android/media/MediaPlayer.html)的规范,我reset在改变时需要玩家dataSource.这样可以正常工作,但只要channelChanged快速连续两次调用该方法,就会MediaPlayer.reset冻结UI.我分析了这里看到的代码:

public void channelChanged(String streamingUrl)
{
    long m1 = System.currentTimeMillis();
    mMediaPlayer.reset();
    long m2 = System.currentTimeMillis();
    try
    {
        mMediaPlayer.setDataSource(streamingUrl);
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }
    long m3 = System.currentTimeMillis();
    mMediaPlayer.prepareAsync();
    long m4 = System.currentTimeMillis();
    Log.d("MEDIAPLAYER", "reset: " + (m2 - m1));
    Log.d("MEDIAPLAYER", "setDataSource: " + (m3 - m2));
    Log.d("MEDIAPLAYER", "preparing: " + (m4 - m3));
}

重置:3

setDataSource:1

准备:0

重置:3119

setDataSource:2

准备:1

显然,第一次呼叫reset被阻止asynchronous preparing(当我等到第一个流开始然后channelChanged()再次呼叫时,一切都很好).

任何想法如何解决问题？我应该在一个单独的线程中执行整个方法吗？基本上我想避免这种情况,因为它似乎不是一个好的编码风格,并且可能会引起一些进一步的问题,例如当用户试图再次启动播放器时,但播放器仍然在reset方法中,另一方面似乎在等待这个asyncPrepare方法.目前尚不清楚玩家的表现如何......

还有其他好的解决方案吗？

Answer 1

MediaPlayer是一个棘手的混蛋.我建议你看一下示例应用程序,通过查看你必须在其周围编写的代码,以获得一致的媒体播放体验,使MediaPlayer的设计变得明显.

如果有的话,在查看样本之后,您会看到当他们想要跳过一个轨道时,它们实际上会重置并释放...

    mPlayer.reset();
    mPlayer.release();

......以及稍后他们准备加载新曲目时......

    try {
          mPlayer.reset();
          mPlayer.setDataSource(someUrl);
          mPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
             @Override
              public void onPrepared(MediaPlayer mediaPlayer) {
                   //bam!
              }
          });
          mPlayer.prepareAsync();
    } catch (IllegalStateException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (IllegalArgumentException e) {
        e.printStackTrace();
    }

我已经添加了try/catch,因为在某些设备/操作系统版本中,MediaPlayer比其他版本更差,有时它只是做了奇怪的事情.你应该有一个能够对这些情况做出反应的接口/监听器

更新:

这是我停止(或暂停)我的音乐播放时使用的方法(主要是从示例应用程序中获取,这是在服务中运行,并且已经过修改以适合我自己的应用程序但仍然如此).

第一种方法使用由两个stop和pause,前者穿过true,后者false

/**
 * Releases resources used by the service for playback. This includes the "foreground service"
 * status and notification, the wake locks and possibly the MediaPlayer.
 *
 * @param releaseMediaPlayer Indicates whether the Media Player should also be released or not
 */
void relaxResources(boolean releaseMediaPlayer) {
    stopForeground(true);
    stopMonitoringPlaybackProgress();
    // stop and release the Media Player, if it's available
    if (releaseMediaPlayer && mPlayer != null) {
        mPlayer.reset();
        mPlayer.release();
        mPlayer = null;
    }
    // we can also release the Wifi lock, if we're holding it
    if (mWifiLock.isHeld()) {
        mWifiLock.release();
    }
}

这是以下内容的一部分processPauseRequest():

if (mState == State.Playing) {
        // Pause media player and cancel the 'foreground service' state.
        mState = State.Paused;
        mPlayer.pause();
        dispatchBroadcastEvent(ServiceConstants.EVENT_AUDIO_PAUSE);//notify broadcast receivers
        relaxResources(false); // while paused, we always retain the mp and notification

这是processStopRequest()(简化)的一部分:

void processStopRequest(boolean force, final boolean stopSelf) {
    if (mState == State.Playing || mState == State.Paused || force) {
        mState = State.Stopped;
        // let go of all resources...
        relaxResources(true);
        currentTrackNotification = null;
        giveUpAudioFocus();         

    }
}

现在核心部分是下一个/跳过......

这就是我做的......

void processNextRequest(final boolean isSkipping) {
    processStopRequest(true, false); // THIS IS IMPORTANT, WE RELEASE THE MP HERE
    mState = State.Retrieving;
    dispatchBroadcastEvent(ServiceConstants.EVENT_TRACK_INFO_LOAD_START);
    // snipped but here you retrieve your next track and when it's ready…
    // you just processPlayRequest() and "start from scratch"

这就是MediaPlayer示例的工作方式(在samples文件夹中找到),我没有遇到任何问题.

话虽这么说,我知道当你说你把整个事情搞得一团糟时我的意思,我已经看到了它,这就是MP越野车.如果你得到一个ANR,我想看看它的日志.

这里的记录是我"开始玩"的方式(很多自定义代码已被省略,但你可以看到MP的东西):"

/**
 * Starts playing the next song.
 */
void beginPlaying(Track track) {
    mState = State.Stopped;
    relaxResources(false); // release everything except MediaPlayer
    try {
        if (track != null) {
            createMediaPlayerIfNeeded();
            mPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
            mPlayer.setDataSource(track.audioUrl);
        } else {
            processStopRequest(true, false); // stop everything! 
            return;
        }
        mState = State.Preparing;
        setUpAsForeground(); //service

        /* STRIPPED ALL CODE FROM REMOTECONTROLCLIENT, AS IT ADDS A LOT OF NOISE :) */

        // starts preparing the media player in the background. When it's done, it will call
        // our OnPreparedListener (that is, the onPrepared() method on this class, since we set
        // the listener to 'this').
        // Until the media player is prepared, we *cannot* call start() on it!
        mPlayer.prepareAsync();
        // We are streaming from the internet, we want to hold a Wifi lock, which prevents
        // the Wifi radio from going to sleep while the song is playing.
        if (!mWifiLock.isHeld()) {
            mWifiLock.acquire();
        }

    } catch (IOException ex) {
        Log.e("MusicService", "IOException playing next song: " + ex.getMessage());
        ex.printStackTrace();
    }
}

最后一点,我注意到,当音频流或源不可用或不可靠时,"媒体播放器会阻止所有内容".

祝好运!如果您有任何具体想要的话,请告诉我.