Android canvas drawBitmap方法详解及实例

public class PoterDuffLoadingView extends View {

 private Resources mResources;
 private Paint mBitPaint;
 private Bitmap mBitmap;

 private int mTotalWidth, mTotalHeight;
 private Bitmap girlBitmap;
 private int girlBitWidth , girlBitHeight;
 private Rect girlSrcRect , girlDesRect;

 public PoterDuffLoadingView(Context context) {
  super(context);
  mResources = getResources();
  initBitmap();
 }

 private void initBitmap() {
  //美女图片的宽和高
  girlBitmap = ((BitmapDrawable)mResources.getDrawable(R.drawable.a1)).getBitmap();
  girlBitWidth = girlBitmap.getWidth();
  girlBitHeight = girlBitmap.getHeight();


 }

 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  canvas.drawBitmap(girlBitmap, girlSrcRect, girlDesRect, null);
 }
 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
 }

 @Override
 protected void onSizeChanged(int w, int h, int oldw, int oldh) {
  Log.d("xxxxxx", "onSizeChanged , w = "+w+" , h = "+h+" , mBitWidth = "+mBitWidth+" , mBitHeight = "+mBitHeight);
  super.onSizeChanged(w, h, oldw, oldh);
  mTotalWidth = w;
  mTotalHeight = h;

  girlSrcRect = new Rect(0, 0, girlBitWidth, girlBitHeight);
  girlDesRect = new Rect(0, 0, girlBitWidth, girlBitHeight);

 }
}

girlSrcRect = new Rect(0, 0, girlBitWidth, girlBitHeight); 

girlDesRect = new Rect(20, 50, 20+girlBitWidth, 50+girlBitHeight);

girlSrcRect = new Rect(girlBitWidth/2, 0, girlBitWidth, girlBitHeight/2);
  girlDesRect = new Rect(20, 50, 20+girlBitWidth, 50+girlBitHeight);

girlSrcRect = new Rect(girlBitWidth/2, 0, girlBitWidth, girlBitHeight/2);
  girlDesRect = new Rect(20, 50, 20+girlBitWidth/2, 50+girlBitHeight/2);