单独设置圆角

UIBezierPath *topmaskPath = [UIBezierPath bezierPathWithRoundedRect:topView.bounds byRoundingCorners:UIRectCornerTopLeft | UIRectCornerToPRight cornerRadii:CGSizeMake(10, 10)];   CAShapeLayer *topmaskLayer = [[CAShapeLayer alloc] init];   topmaskLayer.frame = topView.bounds;   topmaskLayer.path = topmaskPath.CGPath;   topView.layer.mask = topmaskLayer;