众所周知一个媒体播放器新建的几个步骤：
Mediaplayer mp = new MediaPlayer(0 mp.setDatasource(xxx); mp.setDispalyer(xxx); mp.setAudioStreamType(xxx); mp.prepareAsync(); mp.start
这个和activity该如何绑定呢？本文则是通过图库分析，来说明此中明细。
打开图库显得的是一个名字叫MovieActivity的Actiivity，具有activity的的生命周期，而媒体的操作是如何和他们关联起来呢，详见下图（图片长，上传的时候出现了背景黑色的情况，不知道为什么，此处分开贴图，真实图片上传资源那边，0积分下载）：
资源下载地址 ：http://download.csdn.net/detail/loovejava/6272059
从代码看到的和媒体关联的就这这几个生命周期的时候，onCreate() , onResume() ,onPause() ,onDestory()。
onPause在android媒体——图库pause时与服务端断开连接 中有讲述。
onCreate只是进行了初始化，无其他特殊操作
onDestory中则是停止了框架层mediaplayer的播放，并且对其进行状态反初始化的操作。
主要是在两个onResume和onKeyDown方法:
简明的说下，onResume是新建了一个媒体播放器并设置监听。
onKeyDown则是通过监听点击时间，来控制媒体的播放和暂停。
======================================= 下面附上关键代码=========================================================
1、onResume初始化媒体：
packageappsGallery2srccomandroidgallery3dappMovieActivity.java
public void onResume() {
mPlayer.onResume();
super.onResume();
}
packageappsGallery2srccomandroidgallery3dappMoviePlayer.java
public void onResume() {
if (mHasPaused) {
mVideoView.seekTo(mVideoPosition);
mVideoView.resume();
// If we have slept for too long, pause the play
if (System.currentTimeMillis() > mResumeableTime) {
pauseVideo();
}
}
mHandler.post(mProgressChecker);
}
frameworkasecorejavaandroidwidgetViewView.java
public void resume() {
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;
}
}
致此已经初始化完毕
2、onKeyDown的如何操控状态改变呢？
packageappsGallery2srccomandroidgallery3dappMoviePlayer.java
private void playVideo() {
mVideoView.start();
mController.showPlaying();
setProgress();
}
private void pauseVideo() {
mVideoView.pause();
mController.showPaused();
}
... ...
public boolean onKeyDown(int keyCode, KeyEvent event) {
// Some headsets will fire off 7-10 events on a single click
if (event.getRepeatCount() > 0) {
return isMediaKey(keyCode);
}
switch (keyCode) {
case KeyEvent.KEYCODE_HEADSETHOOK:
case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE:
if (mVideoView.isPlaying()) {
pauseVideo();
} else {
playVideo();
}
return true;
case KEYCODE_MEDIA_PAUSE:
if (mVideoView.isPlaying()) {
pauseVideo();
}
return true;
case KEYCODE_MEDIA_PLAY:
if (!mVideoView.isPlaying()) {
playVideo();
}
return true;
case KeyEvent.KEYCODE_MEDIA_PREVIOUS:
case KeyEvent.KEYCODE_MEDIA_NEXT:
// TODO: Handle next / previous accordingly, for now we're
// just consuming the events.
return true;
}
return false;
}
frameworkasecorejavaandroidwidgetViewView.java
@Override
public void start() {
if (isInPlaybackState()) {
mMediaPlayer.start();
mCurrentState = STATE_PLAYING;
}
mTargetState = STATE_PLAYING;
}
@Override
public void pause() {
if (isInPlaybackState()) {
if (mMediaPlayer.isPlaying()) {
mMediaPlayer.pause();
mCurrentState = STATE_PAUSED;
}
}
mTargetState = STATE_PAUSED;
}
至此已经把想操作媒体的意愿发送至mediaPlayer，mediaplayer会进行先关的处理，如何处理，后面播客会详细的讲述。
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看了本文一定有一个疑问，为什么moviePlayer为什么不直接调用mediaplayer的方法呢，为什么中间要隔着一个“第三者”呢?
从上图可以看出videoView继承了SurfaceView，实现了MediaPlayerControl接口，还依赖MediaPlayer
显而易见，我们看到了VideoView就是把媒体，媒体控制和显示的组合体，也可以理解成一个调度类。
我们写如果不使用VideoView的话，自己还得去实现媒体控制的相关操作和显示的相关操作。
here over.