Android清空画布

public void clear()
    {
        Paint paint = new Paint();
        paint.setXfermode(new PorterDuffXfermode(Mode.CLEAR));
        canvas.drawPaint(paint);
        paint.setXfermode(new PorterDuffXfermode(Mode.SRC));

        invalidate();
    }

详细请看：http://trylovecatch.iteye.com/blog/1189452