Android canvas.drawBitmap实现透明效果

以下是针对,‍canvas.drawBitmap方法实施透明效果. 

Paint paint = new Paint(); 
paint.setAlpha(0x40); //设置透明程度
canvas.drawBitmap(this.bitmap, this.offsetX, this.offsetY,paint);

如果是针对图片的drawable,则可以 

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

同理NinePatchDrawable也可以用同样处理. 其实也就是设置画笔(Paint)的透明度.