妳想要那種透明可以看到activity的效果是需要在canvas上設置壹個bitmap才可以的。
Canvas canvas = new Canvas();
canvas.setBitmap(bm_);
p.setColor(Color.TRANSPARENT);
p.setAntiAlias(true);
p.setStyle(Style.FILL);
p.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));
canvas.save();
Rect r = new Rect(0,0,w*2,h*2);
canvas.drawRect(r, p);
canvas_.drawBitmap(bm_, 0, 0,null);