ExoPlayer的使用介绍

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前言：ExoPlayer是google推出的一个应用级的播放框架。接下来我来对它做一个简单的介绍。 ###一，为什么是ExoPlayer？ 1.支持更多的格式 我们知道Android 提供的mediaPlayer只支持有限的格式，比如视频，它支持MP4，3GP。想要播放其他格式的视频还要进行相应的转换。ExoPlayer提供了强大的格式支持。 ExoPlayer支持的媒体格是在多个级别定义的。 从最低层到最高层，分别是：

  • 单个媒体样本的格式（例如，视频帧或音频帧）。 我们称这些样本格式 。 请注意，典型的视频文件将包含至少两种样本格式的媒体; 一个用于视频（例如，H.264）和一个用于音频（例如，AAC）。
  • 容纳媒体样本和相关元数据的容器的格式。 我们称这些容器格式 。 媒体文件具有单个容器格式（例如MP4），通常由文件扩展名指示。 请注意，对于某些仅音频格式（例如MP3），样本和容器格式可能相同。
  • 自适应流技术，如DASH，SmoothStreaming和HLS。 这些不是媒体格式，但是仍然需要定义什么级别的支持ExoPlayer提供。

2.ExoPlayer是java语言编写的，相比与MediaPlayer用Native Code来说，可以更清楚的获得一些异常源和进行部分代码调试。 3.ExoPlayer是开源的，github上地址ExoPlayer遇到问题后可以提交Issues，最近遇到关于SimpleExoPlayer setVideoListener去监听OnVideoSizeChanged()时黑屏有声音，然后提交了一个Issues:The surface show nothing after mSimpleExoPlayer.setVideoListener(mVideoListener),他们很快给了回复，另外开源的代码经过大家的验证，也会更加的健壮。 4.ExoPlayer有强大的开发文档developer guide ，读者也可以根据文档更好的了解它。 ###二，如何使用？ 这里演示一个播放器的简单使用。 ####1.在xml中

<LinearLayout
    android:id="@+id/activity_main"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.songwenju.useexoplayer.MainActivity">

    <com.google.android.exoplayer2.ui.SimpleExoPlayerView
        android:id="@+id/exoView"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <ProgressBar
            android:id="@+id/progressBar"
            android:visibility="gone"
            style="?android:attr/progressBarStyleLarge"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"/>
    </com.google.android.exoplayer2.ui.SimpleExoPlayerView>
</LinearLayout>

这里使用了SimpleExoPlayerView，在其内部添加了一个ProgressBar。 ####2.播放需要的步骤 初始化播放器：

   /**
     * 初始化player
     */
    private void initPlayer() {
        //1. 创建一个默认的 TrackSelector
        BandwidthMeter bandwidthMeter = new DefaultBandwidthMeter();
        TrackSelection.Factory videoTackSelectionFactory =
                new AdaptiveTrackSelection.Factory(bandwidthMeter);
        TrackSelector trackSelector =
                new DefaultTrackSelector(videoTackSelectionFactory);
        LoadControl loadControl = new DefaultLoadControl();
        //2.创建ExoPlayer
        mSimpleExoPlayer = ExoPlayerFactory.newSimpleInstance(this,trackSelector,loadControl);
        //3.创建SimpleExoPlayerView
        mExoPlayerView = (SimpleExoPlayerView) findViewById(R.id.exoView);
        //4.为SimpleExoPlayer设置播放器
        mExoPlayerView.setPlayer(mSimpleExoPlayer);
    }

开始播放：

 private void playVideo() {
        //测量播放过程中的带宽。 如果不需要，可以为null。
        DefaultBandwidthMeter bandwidthMeter = new DefaultBandwidthMeter();
        // 生成加载媒体数据的DataSource实例。
        DataSource.Factory dataSourceFactory
                = new DefaultDataSourceFactory(MainActivity.this,
                Util.getUserAgent(MainActivity.this,"useExoplayer"),bandwidthMeter);
        // 生成用于解析媒体数据的Extractor实例。
        ExtractorsFactory extractorsFactory = new DefaultExtractorsFactory();


        // MediaSource代表要播放的媒体。
        MediaSource videoSource = new ExtractorMediaSource(playerUri,dataSourceFactory,extractorsFactory,
                null,null);
        //Prepare the player with the source.
        mSimpleExoPlayer.prepare(videoSource);
        //添加监听的listener
//        mSimpleExoPlayer.setVideoListener(mVideoListener);
        mSimpleExoPlayer.addListener(eventListener);
//        mSimpleExoPlayer.setTextOutput(mOutput);
        mSimpleExoPlayer.setPlayWhenReady(true);

    }

监听播放器的状态：

 private ExoPlayer.EventListener eventListener = new ExoPlayer.EventListener() {
        @Override
        public void onTimelineChanged(Timeline timeline, Object manifest) {
            LogUtil.i(this,"onTimelineChanged");
        }

        @Override
        public void onTracksChanged(TrackGroupArray trackGroups, TrackSelectionArray trackSelections) {
            LogUtil.i(this,"onTracksChanged");
        }

        @Override
        public void onLoadingChanged(boolean isLoading) {
            LogUtil.i(this,"onLoadingChanged");
        }

        @Override
        public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
            LogUtil.i(this,"onPlayerStateChanged: playWhenReady = "+String.valueOf(playWhenReady)
                    +" playbackState = "+playbackState);
            switch (playbackState){
                case ExoPlayer.STATE_ENDED:
                    LogUtil.i(this,"Playback ended!");
                    //Stop playback and return to start position
                    setPlayPause(false);
                    mSimpleExoPlayer.seekTo(0);
                    break;
                case ExoPlayer.STATE_READY:
                    mProgressBar.setVisibility(View.GONE);
                    LogUtil.i(this,"ExoPlayer ready! pos: "+mSimpleExoPlayer.getCurrentPosition()
                            +" max: "+stringForTime((int)mSimpleExoPlayer.getDuration()));
                    setProgress(0);
                    break;
                case ExoPlayer.STATE_BUFFERING:
                    LogUtil.i(this,"Playback buffering!");
                    mProgressBar.setVisibility(View.VISIBLE);
                    break;
                case ExoPlayer.STATE_IDLE:
                    LogUtil.i(this,"ExoPlayer idle!");
                    break;
            }
        }

        @Override
        public void onPlayerError(ExoPlaybackException error) {
            LogUtil.i(this,"onPlaybackError: "+error.getMessage());
        }

        @Override
        public void onPositionDiscontinuity() {
            LogUtil.i(this,"onPositionDiscontinuity");
        }

        @Override
        public void onPlaybackParametersChanged(PlaybackParameters playbackParameters) {
            LogUtil.i(this,"MainActivity.onPlaybackParametersChanged."+playbackParameters.toString());
        }
    };

mSimpleExoPlayer.addListener(eventListener);

通过监听状态去显示loading条，做错误处理等。

Activity退出时，释放播放器：

   @Override
    protected void onPause() {
        LogUtil.i(this,"MainActivity.onPause.");
        super.onPause();
        mSimpleExoPlayer.stop();
    }

    @Override
    protected void onStop() {
        LogUtil.i(this,"MainActivity.onStop.");
        super.onStop();
        mSimpleExoPlayer.release();
    }

MainActivity完整的代码

public class MainActivity extends AppCompatActivity {
    private SimpleExoPlayerView mExoPlayerView;
    private SimpleExoPlayer mSimpleExoPlayer;
    private Context mContext;
    Uri playerUri = Uri.parse("https://storage.googleapis.com/android-tv/Sample%20videos/Demo%20Slam/Google%20Demo%20Slam_%20Hangin'%20with%20the%20Google%20Search%20Bar.mp4");
    private ProgressBar mProgressBar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.activity_main);
        mContext = this;
        mProgressBar = (ProgressBar) findViewById(R.id.progressBar);
        initPlayer();
        playVideo();

    }

    /**
     * 初始化player
     */
    private void initPlayer() {
        //1. 创建一个默认的 TrackSelector
        BandwidthMeter bandwidthMeter = new DefaultBandwidthMeter();
        TrackSelection.Factory videoTackSelectionFactory =
                new AdaptiveTrackSelection.Factory(bandwidthMeter);
        TrackSelector trackSelector =
                new DefaultTrackSelector(videoTackSelectionFactory);
        LoadControl loadControl = new DefaultLoadControl();
        //2.创建ExoPlayer
        mSimpleExoPlayer = ExoPlayerFactory.newSimpleInstance(this,trackSelector,loadControl);
        //3.创建SimpleExoPlayerView
        mExoPlayerView = (SimpleExoPlayerView) findViewById(R.id.exoView);
        //4.为SimpleExoPlayer设置播放器
        mExoPlayerView.setPlayer(mSimpleExoPlayer);
    }

    private void playVideo() {
        //测量播放过程中的带宽。 如果不需要，可以为null。
        DefaultBandwidthMeter bandwidthMeter = new DefaultBandwidthMeter();
        // 生成加载媒体数据的DataSource实例。
        DataSource.Factory dataSourceFactory
                = new DefaultDataSourceFactory(MainActivity.this,
                Util.getUserAgent(MainActivity.this,"useExoplayer"),bandwidthMeter);
        // 生成用于解析媒体数据的Extractor实例。
        ExtractorsFactory extractorsFactory = new DefaultExtractorsFactory();


        // MediaSource代表要播放的媒体。
        MediaSource videoSource = new ExtractorMediaSource(playerUri,dataSourceFactory,extractorsFactory,
                null,null);
        //Prepare the player with the source.
        mSimpleExoPlayer.prepare(videoSource);
        //添加监听的listener
//        mSimpleExoPlayer.setVideoListener(mVideoListener);
        mSimpleExoPlayer.addListener(eventListener);
//        mSimpleExoPlayer.setTextOutput(mOutput);
        mSimpleExoPlayer.setPlayWhenReady(true);

    }


    TextRenderer.Output mOutput = new TextRenderer.Output() {
        @Override
        public void onCues(List<Cue> cues) {
            LogUtil.i(this,"MainActivity.onCues.");
        }
    };

    private SimpleExoPlayer.VideoListener mVideoListener = new SimpleExoPlayer.VideoListener() {
        @Override
        public void onVideoSizeChanged(int width, int height, int unappliedRotationDegrees, float pixelWidthHeightRatio) {
            LogUtil.i(this,"MainActivity.onVideoSizeChanged.width:"+width+", height:"+height);

        }

        @Override
        public void onRenderedFirstFrame() {
                LogUtil.i(this,"MainActivity.onRenderedFirstFrame.");
        }
    };


    private ExoPlayer.EventListener eventListener = new ExoPlayer.EventListener() {
        @Override
        public void onTimelineChanged(Timeline timeline, Object manifest) {
            LogUtil.i(this,"onTimelineChanged");
        }

        @Override
        public void onTracksChanged(TrackGroupArray trackGroups, TrackSelectionArray trackSelections) {
            LogUtil.i(this,"onTracksChanged");
        }

        @Override
        public void onLoadingChanged(boolean isLoading) {
            LogUtil.i(this,"onLoadingChanged");
        }

        @Override
        public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
            LogUtil.i(this,"onPlayerStateChanged: playWhenReady = "+String.valueOf(playWhenReady)
                    +" playbackState = "+playbackState);
            switch (playbackState){
                case ExoPlayer.STATE_ENDED:
                    LogUtil.i(this,"Playback ended!");
                    //Stop playback and return to start position
                    setPlayPause(false);
                    mSimpleExoPlayer.seekTo(0);
                    break;
                case ExoPlayer.STATE_READY:
                    mProgressBar.setVisibility(View.GONE);
                    LogUtil.i(this,"ExoPlayer ready! pos: "+mSimpleExoPlayer.getCurrentPosition()
                            +" max: "+stringForTime((int)mSimpleExoPlayer.getDuration()));
                    setProgress(0);
                    break;
                case ExoPlayer.STATE_BUFFERING:
                    LogUtil.i(this,"Playback buffering!");
                    mProgressBar.setVisibility(View.VISIBLE);
                    break;
                case ExoPlayer.STATE_IDLE:
                    LogUtil.i(this,"ExoPlayer idle!");
                    break;
            }
        }

        @Override
        public void onPlayerError(ExoPlaybackException error) {
            LogUtil.i(this,"onPlaybackError: "+error.getMessage());
        }

        @Override
        public void onPositionDiscontinuity() {
            LogUtil.i(this,"onPositionDiscontinuity");
        }

        @Override
        public void onPlaybackParametersChanged(PlaybackParameters playbackParameters) {
            LogUtil.i(this,"MainActivity.onPlaybackParametersChanged."+playbackParameters.toString());
        }
    };

    /**
     * Starts or stops playback. Also takes care of the Play/Pause button toggling
     * @param play True if playback should be started
     */
    private void setPlayPause(boolean play){
        mSimpleExoPlayer.setPlayWhenReady(play);
    }

    private String stringForTime(int timeMs) {
        StringBuilder mFormatBuilder;
        Formatter mFormatter;
        mFormatBuilder = new StringBuilder();
        mFormatter = new Formatter(mFormatBuilder, Locale.getDefault());
        int totalSeconds =  timeMs / 1000;

        int seconds = totalSeconds % 60;
        int minutes = (totalSeconds / 60) % 60;
        int hours   = totalSeconds / 3600;

        mFormatBuilder.setLength(0);
        if (hours > 0) {
            return mFormatter.format("%d:%02d:%02d", hours, minutes, seconds).toString();
        } else {
            return mFormatter.format("%02d:%02d", minutes, seconds).toString();
        }
    }

    @Override
    protected void onPause() {
        LogUtil.i(this,"MainActivity.onPause.");
        super.onPause();
        mSimpleExoPlayer.stop();
    }

    @Override
    protected void onStop() {
        LogUtil.i(this,"MainActivity.onStop.");
        super.onStop();
        mSimpleExoPlayer.release();
    }
}

gitHub实例：useExoPlayer。 关注微信公众号，定期为你推荐移动开发相关文章。

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