Question

我正在尝试实施视频播放列表，以便从一个视频到下一个视频顺利过渡。 mediaPlayer对象有一个prepareasync（）方法，似乎预先缓冲视频，以便它可以播放。如何从VideoView对象调用prepareasync方法？我找到的mediaPlayer示例要么不使用VideoView，要么从头开始创建表面。或者这些示例使用mediaPlayer作为videoview eventlisteners的返回参数，这些参数似乎只发生在videoview.play（）之后。我想在调用play方法之前访问videoview的mediaplayer，这样我就可以调用prepareasync（），然后调用play（）。

Answer 1

就像user1023110提到的那样，VideoView是MediaPlayer的包装器。深入了解源代码（因为文档根本没用）我确认它在私有方法内部调用prepareAsync（） openVideo（）：

   private void openVideo() {
    if (mUri == null || mSurfaceHolder == null) {
        // not ready for playback just yet, will try again later
        return;
    }
    // Tell the music playback service to pause
    // TODO: these constants need to be published somewhere in the framework.
    Intent i = new Intent("com.android.music.musicservicecommand");
    i.putExtra("command", "pause");
    mContext.sendBroadcast(i);

    // we shouldn't clear the target state, because somebody might have
    // called start() previously
    release(false);
    try {
        mMediaPlayer = new MediaPlayer();
        if (mAudioSession != 0) {
            mMediaPlayer.setAudioSessionId(mAudioSession);
        } else {
            mAudioSession = mMediaPlayer.getAudioSessionId();
        }
        mMediaPlayer.setOnPreparedListener(mPreparedListener);
        mMediaPlayer.setOnVideoSizeChangedListener(mSizeChangedListener);
        mMediaPlayer.setOnCompletionListener(mCompletionListener);
        mMediaPlayer.setOnErrorListener(mErrorListener);
        mMediaPlayer.setOnInfoListener(mOnInfoListener);
        mMediaPlayer.setOnBufferingUpdateListener(mBufferingUpdateListener);
        mCurrentBufferPercentage = 0;
        mMediaPlayer.setDataSource(mContext, mUri, mHeaders);
        mMediaPlayer.setDisplay(mSurfaceHolder);
        mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        mMediaPlayer.setScreenOnWhilePlaying(true);
        mMediaPlayer.prepareAsync();
        // we don't set the target state here either, but preserve the
        // target state that was there before.
        mCurrentState = STATE_PREPARING;
        attachMediaController();
    } catch (IOException ex) {
        Log.w(TAG, "Unable to open content: " + mUri, ex);
        mCurrentState = STATE_ERROR;
        mTargetState = STATE_ERROR;
        mErrorListener.onError(mMediaPlayer, MediaPlayer.MEDIA_ERROR_UNKNOWN, 0);
        return;
    } catch (IllegalArgumentException ex) {
        Log.w(TAG, "Unable to open content: " + mUri, ex);
        mCurrentState = STATE_ERROR;
        mTargetState = STATE_ERROR;
        mErrorListener.onError(mMediaPlayer, MediaPlayer.MEDIA_ERROR_UNKNOWN, 0);
        return;
    }
}

Answer 2

VideoView是MediaPlayer和SurfaceView的包装器，因此您无需自己动手。我相信当你调用setVideoURI时，包装器会做好准备。可以通过onPrepared事件处理程序获取VideoView中的媒体播放器，一旦你得到它，我想你可以在第一次之后调用自己做好准备，但是我认为内部结构很棘手并没有很好的记录，所以事情可能会没有按预期工作。

从VideoView调用MediaPlayer.PrepareAsync

2 个答案: