Android游戏开发之旅（九）VideoView类剖析

有关SurfaceView 相关的内容今天Android123继续延用系统 的示例类VideoView来让大家深入了解Android平台 的图形绘制基础类的实现原理。大家可能会发现VideoView类的控制方面无法改变，我们可以通过重构VideoView类来实现更个性化的播放 器

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; }