我花了几个小时试图破解原始 VideoView 源代码，现在我可以确认 VideoView 可以被破解以执行您想要的操作 - 在表面被破坏后保留缓冲。我已经在我的三星 Galaxy S2 上进行了测试，它按预期工作，在我的情况下，当我打开一个新活动并返回时，视频缓冲（从远程 http 服务器流式传输 m4v 视频）成功保留。
基本上，解决方法是创建您自己的 VideoView 类（通过复制源代码），并破解 SurfaceHolder.Callback() 实现。请记住，VideoView 使用一些内部/隐藏 API，因此如果您想在自己的项目中创建 VideoView 的副本，您必须按照inazaruk's article 启用使用内部/隐藏 API。作为一个快速破解，我只需从 here 下载 inazaruk 的构建并使用 inazaruk-android-sdk-dbd50d4/platforms/android-15-internals/android.jar 替换我的 android-sdk/platforms/android 中的原始 android.jar -15/.
VideoView源码可以从GrepCode下载。成功创建自己的副本且没有编译错误后，将 SurfaceHolder.Callback() 更改为如下内容：
private boolean videoOpened = false;
SurfaceHolder.Callback mSHCallback = new SurfaceHolder.Callback()
{
... ...
public void surfaceCreated(SurfaceHolder holder)
{
Log.i(TAG, "---------------------> surface created.");
mSurfaceHolder = holder;
if (!videoOpened) {
openVideo(); // <-- if first time opened, do something as usual, video is buffered.
/**
* openVideo() actually mMediaPlayer.prepareAsync() is the first key point, it is
* also called in other two VideoView's public methods setVideoURI() and resume(),
* make sure you don't call them in your activity.
*/
videoOpened = true;
} else {
start(); // <-- if back from another activity, simply start it again.
}
}
public void surfaceDestroyed(SurfaceHolder holder)
{
Log.i(TAG, "---------------------> surface destroyed.");
// after we return from this we can't use the surface any more.
mSurfaceHolder = null;
if (mMediaController != null) mMediaController.hide();
//release(true);
/**
* release() actually mMediaPlayer.release() is the second key point, it is also
* called in other two VideoView's public methods stopPlayback() and suspend(), make
* sure you don't call them in your activity.
*/
pause(); // <-- don't release, just pause.
}
};
并确保不要像这样在 MediaPlayerActivity 中显式调用 videoView.resume()、videoView.setVideoURI()、videoView.suspend() 和 videoView.stopPlayback()：
@Override
protected void onResume() {
if (videoView != null)
videoView.resume(); // <-- this will cause re-buffer.
super.onResume();
}
@Override
protected void onPause() {
if (videoView != null)
videoView.suspend(); // <-- this will cause clear buffer.
super.onPause();
}
请注意，我刚刚做了一个肮脏的黑客来证明可行性，您应该正确设计和实现您的 VideoView 类以避免任何副作用。
更新：
作为替代方案，您应该能够使用普通 MediaPlayer 创建您的 MediaPlayerActivity 如果您不想执行 interal/hide API 的东西您可以从 ApiDemos 示例中的 MediaPlayerDemo_Video.java 开始。关键是确保在 SurfaceHolder 回调方法和 Activity 生命周期方法中正确处理准备（结果缓冲）和释放方法，以避免每次创建/销毁表面以及启动、恢复/暂停活动时准备/释放视频，停了下来。我创建了一个虚拟的 BufferedMediaPlayerActivity （高度简化，以便在此处发布），它只包含关键部分，可用于快速演示，它没有 MediaController，但是，您可以从 Logcat 中查看缓冲区百分比实际上保持不变每次打开新活动并返回时，都会增加而不是从 0 滚动。
BufferedMediaPlayerActivity.java：
package com.example;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnBufferingUpdateListener;
import android.media.MediaPlayer.OnPreparedListener;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class BufferedMediaPlayerActivity extends Activity implements OnPreparedListener, OnBufferingUpdateListener, SurfaceHolder.Callback {
private static final String TAG = "BufferedMediaPlayerActivity";
private int mVideoWidth;
private int mVideoHeight;
private MediaPlayer mMediaPlayer;
private SurfaceView mPreview;
private SurfaceHolder holder;
private String path;
private boolean mIsVideoReadyToBePlayed = false;
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.buffered_media_player);
mPreview = (SurfaceView) findViewById(R.id.surface);
holder = mPreview.getHolder();
holder.addCallback(this);
holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
holder.setFixedSize(mVideoWidth, mVideoHeight);
// retrieve httpUrl passed from previous activity.
path = getIntent().getExtras().getString("videoUrl");
}
@Override
public void onDestroy() {
super.onDestroy();
if (mMediaPlayer != null) {
mMediaPlayer.release();
mMediaPlayer = null;
}
mIsVideoReadyToBePlayed = false;
}
private void playVideo() {
mIsVideoReadyToBePlayed = false;
try {
// Create a new media player and set the listeners
mMediaPlayer = new MediaPlayer();
mMediaPlayer.setDataSource(path);
mMediaPlayer.setDisplay(holder);
mMediaPlayer.prepare();
mMediaPlayer.setOnPreparedListener(this);
mMediaPlayer.setOnBufferingUpdateListener(this);
mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
} catch (Exception e) {
Log.e(TAG, "error: " + e.getMessage(), e);
}
}
@Override
public void onPrepared(MediaPlayer mediaplayer) {
Log.d(TAG, "onPrepared called");
mIsVideoReadyToBePlayed = true;
if (mIsVideoReadyToBePlayed) {
mMediaPlayer.start();
}
}
@Override
public void onBufferingUpdate(MediaPlayer mp, int percent) {
Log.i(TAG, "---------------> " + percent);
}
@Override
public void surfaceChanged(SurfaceHolder surfaceholder, int i, int j, int k) {
Log.d(TAG, "surfaceChanged called");
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
Log.d(TAG, "surfaceCreated called");
if (!mIsVideoReadyToBePlayed)
playVideo();
else
mMediaPlayer.start();
}
@Override
public void surfaceDestroyed(SurfaceHolder surfaceholder) {
Log.d(TAG, "surfaceDestroyed called");
mMediaPlayer.pause();
}
}
buffered_media_player.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<SurfaceView android:id="@+id/surface"
android:layout_width="200dip"
android:layout_height="160dip"
android:layout_gravity="center">
</SurfaceView>
</LinearLayout>