Android 从头搭建视频播放器——SystemMediaPlayerImpl

Posted 2022-12-15 牧秦丶

【android】 从头搭建视频播放器（2）——SystemMediaPlayerImpl

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转载请注明出处：http://blog.csdn.net/arnozhang12/article/details/48734139
 
 

1、MediaPlayer 简介

        首先，我们基于系统的 android.media.MediaPlayer 实现我们的 BaseMediaPlayer。当然，我们也可以使用其他第三方的 Player 来实现，具体就在实际使用中按需求来做。

        那么，我们需要先对 MediaPlayer 做一些必要的了解。通过网上的资料搜索，我认为这篇文章对 MediaPlayer 的各种状态迁移和使用规范做了较好的阐述：

[译]class android.media.MediaPlayer

        我从这篇文章里面借了一张图如下：

        通过对上图的理解，结合播放器的功能特性，抽离出了主要的状态迁移如下：

        我们着重需要关注的方法列表如下：

方法	特性
new MediaPlayer()创建一个 MediaPlayer，处于 Idle 状态
reset()	重置 MediaPlayer，使其切换到 Idle 状态
setDataSource(context, uri)	设置视频数据源，切换到 Initialized 状态
prepare()	准备数据，同步方法，完成后将切换到 Prepared 状态
prepareAsync()	异步准备数据，处于 Preparing 状态，准备完毕后通过回调 OnPreparedListener.onPrepared 方法，处于 Prepared 状态
start()	开始/恢复播放，切换到 Started 状态
seekTo(millSeconds)	跳转进度
pause()	暂停播放，切换到 Paused 状态
stop()	停止播放，切换到 Stopped 状态
release()	释放播放器资源，切换到终止 End 状态，这时候不允许对 MediaPlayer 做任何操作了
setDisplay(surfaceHolder)	设置画面展示 SurfaceHolder

2、关注的回调

         MediaPlayer 有众多回调 Listener，我们需要着重关注：

回调	特性
MediaPlayer.OnPreparedListener	视频通过 prepareAsync 异步准备好之后回调
MediaPlayer.OnCompletionListener	视频播放完成后的回调
MediaPlayer.OnVideoSizeChangedListener	视频画面大小更改的回调，我们一般通过这个回调更改 SurfaceView 的大小及位置，以达到等比例缩放播放的效果
MediaPlayer.OnBufferingUpdateListener	视频缓冲进度更改回调，一般我们通过这个回调更改 SeekBar 的 SecondaryProgress
MediaPlayer.OnErrorListener	播放器内部发生错误回调，一般是错误的调用或者其他错误引起

3、使用 MediaPlayer 必需的步骤

        接下来我们基于系统的 MediaPlayer 实现 SystemMediaPlayerImpl，它继承自 BaseMediaPlayer。一般使用 MediaPlayer 有如下步骤：

步骤	内容
初始化	new MediaPlayer
设置一系列 Listener	OnPreparedListener 等等
设置数据源	setDataSource. 可以是本地文件，也可以是网络数据 Url
处理 OnPreparedListener.onPrepared 回调	设置画面展示 SurfaceHolder，并调用 start 开始播放。如果需要从视频的某个位置播放，可在这里调用 seekTo(millSeconds) 直接跳转
处理 OnVideoSizeChangedListener.onVideoSizeChanged 回调	在此通过获取到的视频画面大小调整 SurfaceView 的位置及大小，达到等比例缩放的效果
处理 OnBufferingUpdateListener.onBufferingUpdate 回调	再次可以更新界面上的进度条的缓冲进度
处理 OnCompletionListener.onCompletion 回调	在此处理播放完成通知，可以按需求来做按章节连续播放或者退出页面等等上层业务逻辑
处理 OnErrorListener.onError 回调	处理错误，进行 UI 的展示更新等等

4、SystemMediaPlayerImpl

        我们根据上面的步骤，结合 上一篇文章 中介绍的 BaseMediaPlayer，实现出 SystemMediaPlayerImpl 如下：

/**
 * SystemMediaPlayerImpl.java
 *
 * @author arnozhang
 * @email  [e-mail]
 * @date   2015.9.25
 */
public class SystemMediaPlayerImpl extends BaseMediaPlayer 

    private MediaPlayer mMediaPlayer;


    public SystemMediaPlayerImpl(Context context, SurfaceView surfaceView) 
        super(context, surfaceView);

        init();
    

    private void init() 
        mMediaPlayer = new MediaPlayer();
        mMediaPlayer.setAudiostreamType(AudioManager.STREAM_MUSIC);
        mMediaPlayer.setOnPreparedListener(onPreparedListener);
        mMediaPlayer.setOnVideoSizeChangedListener(mOnVideoSizeChangedListener);
        mMediaPlayer.setOnBufferingUpdateListener(mOnBufferingUpdateListener);
        mMediaPlayer.setOnErrorListener(mOnErrorListener);
        mMediaPlayer.setOnCompletionListener(mOnCompletionListener);
    

    @Override
    public void play(VideoInfo videoInfo) 
        if (mMediaPlayer == null) 
            return;
        

        super.play(videoInfo);

        // Clear old display and Reset.
        mMediaPlayer.setDisplay(null);
        mMediaPlayer.reset();

        try 
            mMediaPlayer.setDataSource(mContext, Uri.parse(videoInfo.getCurrentStreamUrl()));
         catch (IOException e) 
            e.printStackTrace();
        

        // Prepare For Play.
        mMediaPlayer.prepareAsync();
        notifyStartPlay();
        notifyLoading();
    

    @Override
    public void pause() 
        if (mMediaPlayer == null || !mMediaPlayerIsPrepared) 
            return;
        

        if (mMediaPlayer.isPlaying()) 
            mMediaPlayer.pause();
            notifyPaused();
        
    

    @Override
    public void resume() 
        if (mMediaPlayer == null || !mMediaPlayerIsPrepared) 
            return;
        

        mMediaPlayer.start();
        notifyResumed();
    

    @Override
    public void stop() 
        if (mMediaPlayer == null) 
            return;
        

        if (mMediaPlayer.isPlaying()) 
            mMediaPlayer.stop();
        

        notifyStopped();
    

    @Override
    public void seekTo(int millSeconds) 
        if (mMediaPlayer != null) 
            mMediaPlayer.seekTo(millSeconds);
        
    

    @Override
    public void setVolume(float volume) 
        if (mMediaPlayer != null) 
            mMediaPlayer.setVolume(volume, volume);
        
    

    @Override
    public int getDuration() 
        return mMediaPlayer != null ? mMediaPlayer.getDuration() : 0;
    

    @Override
    public int getCurrentPosition() 
        return mMediaPlayer != null ? mMediaPlayer.getCurrentPosition() : 0;
    

    @Override
    public void doDestroy() 
        clearLoadingFailed();
        mMediaPlayer.release();
        mMediaPlayer = null;
    

    @Override
    public boolean isPlaying() 
        return mMediaPlayer != null && mMediaPlayer.isPlaying();
    

    @Override
    protected void playWithDisplayHolder(SurfaceHolder holder) 
        mMediaPlayer.setDisplay(holder);
        mMediaPlayer.setScreenOnWhilePlaying(true);
        mMediaPlayer.start();
        mMediaPlayer.seekTo(0);

        trySeekToStartPosition();
    

    private void clearLoadingFailed() 
        ThreadManager.getInstance().getUIHandler().removeCallbacks(mLoadingFailedRunnable);
    

    MediaPlayer.OnPreparedListener onPreparedListener = new MediaPlayer.OnPreparedListener() 
        public void onPrepared(MediaPlayer player) 
            mAutoPlayWhenHolderCreated = false;
            mMediaPlayerIsPrepared = true;
            mIsLoading = false;

            clearLoadingFailed();
            notifyFinishLoading();

            // Start Play.
            SurfaceHolder holder = mSurfaceView.getHolder();
            if (holder == null) 
                mAutoPlayWhenHolderCreated = true;
             else 
                playWithDisplayHolder(holder);
            
        
    ;

    private void trySeekToStartPosition() 
        int seekToPosition = mVideoInfo.getCurrentPosition();
        if (mMediaPlayer != null && mMediaPlayerIsPrepared && mVideoSizeInitialized && seekToPosition > 0) 
            mMediaPlayer.seekTo(seekToPosition);
        
    

    MediaPlayer.OnCompletionListener mOnCompletionListener =
            new MediaPlayer.OnCompletionListener() 
                public void onCompletion(MediaPlayer player) 
                    player.seekTo(0);
                    notifyPlayComplete();
                
            ;

    MediaPlayer.OnVideoSizeChangedListener mOnVideoSizeChangedListener =
            new MediaPlayer.OnVideoSizeChangedListener() 
                public void onVideoSizeChanged(MediaPlayer player, int width, int height) 
                    mVideoWidth = player.getVideoWidth();
                    mVideoHeight = player.getVideoHeight();

                    updateSurfaceSize();

                    mVideoSizeInitialized = true;
                    trySeekToStartPosition();
                
            ;

    MediaPlayer.OnBufferingUpdateListener mOnBufferingUpdateListener =
            new MediaPlayer.OnBufferingUpdateListener() 
                public void onBufferingUpdate(MediaPlayer player, int percent) 
                    mBufferPercent = percent;
                
            ;

    MediaPlayer.OnErrorListener mOnErrorListener = new MediaPlayer.OnErrorListener() 
        public boolean onError(MediaPlayer player, int what, int extra) 
            String errorWhat;
            switch (what) 
                case 1:
                    errorWhat = "MEDIA_ERROR_UNKNOWN";
                    break;
                case 100:
                    errorWhat = "MEDIA_ERROR_SERVER_DIED";
                    break;
                default:
                    errorWhat = "!";
            

            String errorExtra;
            switch (extra) 
                case -1010:
                    errorExtra = "MEDIA_ERROR_UNSUPPORTED";
                    break;
                case -1007:
                    errorExtra = "MEDIA_ERROR_MALFORMED";
                    break;
                case -1004:
                    errorExtra = "MEDIA_ERROR_IO";
                    break;
                case -110:
                    errorExtra = "MEDIA_ERROR_TIMED_OUT";
                    break;
                default:
                    errorExtra = "!";
            

            String msg = String.format("what:%#x,%s extra:%#x,%s", what, errorWhat, extra, errorExtra);
            notifyError(what, msg);
            return true;
        
    ;

        下一篇我们将介绍手势检测与控制。