自定义view清屏

Paint p =new Paint();

//清屏

p.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));

canvas.drawPaint(p);

p.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));

//清屏后view显示黑色背景重新定义

canvas.drawColor(Color.WHITE);