Android canvas.drawBitmap兑现透明效果

Android canvas.drawBitmap实现透明效果
以下是针对,?canvas.drawBitmap方法实施透明效果.

Drawable ibSelected; ...定义DrawableibSelected.setBounds(0, 0, itemImageWidth+2, itemImageHeight+2);((BitmapDrawable)ibSelected).getPaint().setAlpha(0x40);ibSelected.draw(canvas);