Android 音视频开发

Android 音视频开发 - VideoView

本篇文章主要介绍下Android 中的VideoView.

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.

<VideoViewandroid: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:

setVideoURI(Uri uri)
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 laterreturn;}// we shouldn't clear the target state, because somebody might have// called start() previouslyrelease(false);if (mAudioFocusType != AudioManager.AUDIOFOCUS_NONE) {// TODO this should have a focus listenermAudioManager.requestAudioFocus(null, mAudioAttributes, mAudioFocusType, 0 /*flags*/);}try {mMediaPlayer = new MediaPlayer();// TODO: create SubtitleController in MediaPlayer, but we need// a context for the subtitle renderersfinal 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()

release()方法释放正在播放的视频.
初始化mMediaPlayer,传入Uri,设置状态 STATE_PREPARING。
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：

创建一个MediaController对象：MediaController mediaController = new MediaController(context);
将MediaController与媒体播放器组件关联：mediaController.setMediaPlayer(mediaPlayer);
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();
}