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有關SurfaceView 相關的內容今天Android123繼續延用系統 的示例類VideoView來讓大家深入了解Android平臺 的圖形繪制基礎類的實現原理。大家可能會發現VideoView類的控制方面無法改變，我們可以通過重構VideoView類來實現更個性化的播放 器

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public class VideoView extends SurfaceView implements MediaPlayerControl {  
  private String TAG = "VideoView";  
  // settable by the client  
  private Uri        mUri;  
  private int        mDuration;  
  // all possible internal states  
  private static final int STATE_ERROR              = -1;  
  private static final int STATE_IDLE              = 0;  
  private static final int STATE_PREPARING          = 1;  
  private static final int STATE_PREPARED          = 2;  
  private static final int STATE_PLAYING            = 3;  
  private static final int STATE_PAUSED            = 4;  
  private static final int STATE_PLAYBACK_COMPLETED = 5;  
  // mCurrentState is a VideoView object's current state.  
  // mTargetState is the state that a method caller intends to reach.  
  // For instance, regardless the VideoView object's current state,  
  // calling pause() intends to bring the object to a target state  
  // of STATE_PAUSED.  
  private int mCurrentState = STATE_IDLE;  
  private int mTargetState  = STATE_IDLE;  
  // All the stuff we need for playing and showing a video  
  private SurfaceHolder mSurfaceHolder = null;  
  private MediaPlayer mMediaPlayer = null;  
  private int        mVideoWidth;  
  private int        mVideoHeight;  
  private int        mSurfaceWidth;  
  private int        mSurfaceHeight;  
  private MediaController mMediaController;  
  private OnCompletionListener mOnCompletionListener;  
  private MediaPlayer.OnPreparedListener mOnPreparedListener;  
  private int        mCurrentBufferPercentage;  
  private OnErrorListener mOnErrorListener;  
  private int        mSeekWhenPrepared;  // recording the seek position while preparing  
  private boolean    mCanPause;  
  private boolean    mCanSeekBack;  
  private boolean    mCanSeekForward;  
  public VideoView(Context context) {  
      super(context);  
      initVideoView();  
  }  
 
  public VideoView(Context context, AttributeSet attrs) {  
      this(context, attrs, 0);  
      initVideoView();  
  }  
 
  public VideoView(Context context, AttributeSet attrs, int defStyle) {  
      super(context, attrs, defStyle);  
      initVideoView();  
  }  
  @Override 
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {  
      //Log.i("@@@@", "onMeasure");  
      int width = getDefaultSize(mVideoWidth, widthMeasureSpec);  
      int height = getDefaultSize(mVideoHeight, heightMeasureSpec);  
      if (mVideoWidth > 0 && mVideoHeight > 0) {  
          if ( mVideoWidth * height  > width * mVideoHeight ) {  
              //Log.i("@@@", "image too tall, correcting");  
              height = width * mVideoHeight / mVideoWidth;  
          } else if ( mVideoWidth * height  < width * mVideoHeight ) {  
              //Log.i("@@@", "image too wide, correcting");  
              width = height * mVideoWidth / mVideoHeight;  
          } else {  
              //Log.i("@@@", "aspect ratio is correct: " +  
                      //width+"/"+height+"="+  
                      //mVideoWidth+"/"+mVideoHeight);  
          }  
      }  
      //Log.i("@@@@@@@@@@", "setting size: " + width + 'x' + height);  
      setMeasuredDimension(width, height);  
  }  
 
  public int resolveAdjustedSize(int desiredSize, int measureSpec) {  
      int result = desiredSize;  
      int specMode = MeasureSpec.getMode(measureSpec);  
      int specSize =  MeasureSpec.getSize(measureSpec);  
      switch (specMode) {  
          case MeasureSpec.UNSPECIFIED:  
              /* Parent says we can be as big as we want. Just don't be larger 
              * than max size imposed on ourselves. 
              */ 
              result = desiredSize;  
              break;  
          case MeasureSpec.AT_MOST:  
              /* Parent says we can be as big as we want, up to specSize. 
              * Don't be larger than specSize, and don't be larger than 
              * the max size imposed on ourselves. 
              */ 
              result = Math.min(desiredSize, specSize);  
              break;  
              
          case MeasureSpec.EXACTLY:  
              // No choice. Do what we are told.  
              result = specSize;  
              break;  
      }  
      return result;  

本文來自CSDN博客，轉載請標明出處：http://blog.csdn.net/JavaTiger427/archive/2010/11/25/6034570.aspx

                                                                                                       --    學海無涯