1: VideoView简介

VideoView是一个用于播放视频的视图组件，可以方便地在应用程序中播放本地或网络上的视频文件。

VideoView可以直接在布局文件中使用，也可以在代码中动态创建。

它封装了MediaPlayer和SurfaceView，提供了简单的接口来控制视频的播放和显示。

它提供了一系列方法来控制视频的播放、暂停、停止等操作，并且支持全屏播放和视频控制器的显示。

VideoView播放视频非常简单，只需要指定视频的URL或本地路径.

2: 使用

以下是VideoView的简单使用:

2.1 布局

在XML布局文件中添加VideoView组件.

<VideoView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    android:id="@+id/videoview"
    />

2.2 设置视频源

代码如下:

videoView = findViewById(R.id.videoview);
videoView.setVideoPath("sdcard/test.mp4");

除了setVideoPath外,我们还可以调用:

  1. setVideoURI(Uri uri)
  2. setVideoURI(Uri uri, Map<String, String> headers)

当然不管是setVideoPath或者setVideoURI实际都是执行的setVideoURI(Uri uri, Map<String, String> headers).

源码如下:

/**
 * Sets video path.
 *
 * @param path the path of the video.
 */
public void setVideoPath(String path) {
    setVideoURI(Uri.parse(path));
}
/**
 * Sets video URI.
 *
 * @param uri the URI of the video.
 */
public void setVideoURI(Uri uri) {
    setVideoURI(uri, null);
}

2.3 播放视频

videoView.start();

我们可以看下start()的源码:

@Override
public void start() {
    if (isInPlaybackState()) {
        mMediaPlayer.start();
        mCurrentState = STATE_PLAYING;
    }
    mTargetState = STATE_PLAYING;
}

可以看到实际上调用mMediaPlayer.start();另外设置了当前的状态为STATE_PLAYING.

这里直接调用了mMediaPlayer.start();那mMediaPlayer是什么时机初始化的呢?

查看源码可以看到:

private void openVideo() {
    if (mUri == null || mSurfaceHolder == null) {
        // not ready for playback just yet, will try again later
        return;
    }
    // we shouldn't clear the target state, because somebody might have
    // called start() previously
    release(false);
    if (mAudioFocusType != AudioManager.AUDIOFOCUS_NONE) {
        // TODO this should have a focus listener
        mAudioManager.requestAudioFocus(null, mAudioAttributes, mAudioFocusType, 0 /*flags*/);
    }
    try {
        mMediaPlayer = new MediaPlayer();
        // TODO: create SubtitleController in MediaPlayer, but we need
        // a context for the subtitle renderers
        final Context context = getContext();
        final SubtitleController controller = new SubtitleController(
                context, mMediaPlayer.getMediaTimeProvider(), mMediaPlayer);
        controller.registerRenderer(new WebVttRenderer(context));
        controller.registerRenderer(new TtmlRenderer(context));
        controller.registerRenderer(new Cea708CaptionRenderer(context));
        controller.registerRenderer(new ClosedCaptionRenderer(context));
        mMediaPlayer.setSubtitleAnchor(controller, this);
        if (mAudioSession != 0) {
            mMediaPlayer.setAudioSessionId(mAudioSession);
        } else {
            mAudioSession = mMediaPlayer.getAudioSessionId();
        }
        mMediaPlayer.setOnPreparedListener(mPreparedListener);
        mMediaPlayer.setOnVideoSizeChangedListener(mSizeChangedListener);
        mMediaPlayer.setOnCompletionListener(mCompletionListener);
        mMediaPlayer.setOnErrorListener(mErrorListener);
        mMediaPlayer.setOnInfoListener(mInfoListener);
        mMediaPlayer.setOnBufferingUpdateListener(mBufferingUpdateListener);
        mCurrentBufferPercentage = 0;
        mMediaPlayer.setDataSource(mContext, mUri, mHeaders);
        mMediaPlayer.setDisplay(mSurfaceHolder);
        mMediaPlayer.setAudioAttributes(mAudioAttributes);
        mMediaPlayer.setScreenOnWhilePlaying(true);
        mMediaPlayer.prepareAsync();
        for (Pair<InputStream, MediaFormat> pending: mPendingSubtitleTracks) {
            try {
                mMediaPlayer.addSubtitleSource(pending.first, pending.second);
            } catch (IllegalStateException e) {
                mInfoListener.onInfo(
                        mMediaPlayer, MediaPlayer.MEDIA_INFO_UNSUPPORTED_SUBTITLE, 0);
            }
        }
        // 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;
    } finally {
        mPendingSubtitleTracks.clear();
    }
}

可以看到openVideo()

  1. release()方法释放正在播放的视频.
  2. 初始化mMediaPlayer,传入Uri,设置状态 STATE_PREPARING。
  3. attachMediaController()绑定MediaPlayer与VideoView。

最后openVideo()则是在setVideoURI(Uri uri, Map<String, String> headers)内调用。

这样其实已经可以播放指定的视频了。

下面的方法可选。

2.4 MediaController控制器

MediaController是一个用于控制媒体播放器的视图组件。

MediaController的使用步骤如下：

  1. 创建一个MediaController对象：MediaController mediaController = new MediaController(context);
  2. 将MediaController与媒体播放器组件关联：mediaController.setMediaPlayer(mediaPlayer);
  3. 将MediaController添加到布局中：layout.addView(mediaController);
videoView.setMediaController(new MediaController(this));
videoView.start().

直接调用setMediaController,运行后我们可以看到与之前直接调用start()的区别就是多了个控制器的显示。其中包含一组常用的媒体控制按钮，如播放/暂停、快进/快退、前进/后退等，并且可以与MediaPlayer或VideoView等媒体播放器组件进行关联.

我们可以看下源码：

public void setMediaController(MediaController controller) {
    if (mMediaController != null) {
        mMediaController.hide();
    }
    mMediaController = controller;
    attachMediaController();
}

可以看到做的操作如下：

  1. 如果存在mMediaController，则调用hide方法。
  2. 对mMediaController赋值
  3. attachMediaController