一尘不染

Android MediaPlayer重置冻结UI

java

MediaPlayer更换dataSource播放器时,Android
出现问题。根据MediaPlayerhttp://developer.android.com/reference/android/media/MediaPlayer.html)的规范,reset更改时我必须对播放器进行操作dataSource。这可以正常工作,但是一旦channelChanged快速连续两次调用该方法,就会MediaPlayer.reset冻结UI。我分析了代码,如下所示:

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));
}

重设:3

setDataSource:1

准备:0

重置:3119

setDataSource:2

准备:1

因此,显然,第一个调用reset被阻止了asynchronous preparing(当我等到第一个流开始然后channelChanged()再次调用时,一切都很好)。

有什么想法如何解决问题?我应该在单独的线程中执行整个方法吗?基本上,我想避免这种情况,因为这似乎不是一种好的编码风格,并且可能会引起一些其他问题,例如,当用户尝试再次启动播放器时,但播放器仍处于该reset方法中,而另一方面似乎在等待asyncPrepare方法。尚不清楚玩家的行为方式…

还有其他好的解决方案吗?


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2020-12-03

共1个答案

一尘不染

MediaPlayer是一个棘手的混蛋。我建议您看一下示例应用程序,其中的MediaPlayer不良设计可以通过查看为确保一致的媒体播放体验而必须编写的乱七八糟的代码而变得明显。

如果有什么需要,在查看示例之后,您会发现当他们想要跳过曲目时,他们实际上会 重置 并释放……

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

…以及以后准备加载新曲目时…

    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();
    }

我添加了try /
catch,因为在某些设备/操作系统版本上,MediaPlayer比其他版本差,有时它只是做一些奇怪的事情。您应该具有能够对这些情况做出反应的接口/侦听器

更新

这是我停止(或暂停)音乐播放时使用的一种方法(主要是从示例应用程序中获取,该程序正在服务中运行,并且已对其进行了修改以适合我自己的应用程序,但仍然可以)。

stop和都使用第一种方法pause,前者通过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…

这就是我的工作

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示例的操作方式(位于samples文件夹中),我没有遇到任何问题。

话虽这么说,但我知道您的意思,当您说整个过程都受阻时,我已经看到了,这是MP的错误。如果您收到ANR,我想查看它的日志。

作为记录,这是我“开始演奏”的方式(已省略了许多自定义代码,但您可以看到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,就会发生“阻止所有内容的媒体播放器”。

祝好运!让我知道您是否想查看任何特定内容。

2020-12-03