有时候layer.cornerRadius并不能满足需求,自己实现drawRect又太麻烦,怎么办?

多的不说,直接上代码:

 

- (void)dwMakeBottomRoundCornerWithRadius:(CGFloat)radius
{
    CGSize size = self.frame.size;
    CAShapeLayer *shapeLayer = [CAShapeLayer layer];
    [shapeLayer setFillColor:[[UIColor whiteColor] CGColor]];
    
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathMoveToPoint(path, NULL, size.width - radius, size.height);
    CGPathAddArc(path, NULL, size.width-radius, size.height-radius, radius, M_PI/2, 0.0, YES);
    CGPathAddLineToPoint(path, NULL, size.width, 0.0);
    CGPathAddLineToPoint(path, NULL, 0.0, 0.0);
    CGPathAddLineToPoint(path, NULL, 0.0, size.height - radius);
    CGPathAddArc(path, NULL, radius, size.height - radius, radius, M_PI, M_PI/2, YES);
    CGPathCloseSubpath(path);
    [shapeLayer setPath:path];
    CFRelease(path);
    self.layer.mask = shapeLayer;//layer的mask,顾名思义,是种位掩蔽,在shapeLayer的填充区域中,alpha值不为零的部分,self会被绘制;alpha值为零的部分,self不会被绘制
}

- (id)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame])
    {
        [self dwMakeBottomRoundCornerWithRadius:3.0];
    }
    return self;
}

这样就能切出一个只有下半部圆角的View

这种方法,只要稍作修改就能实现很多效果,比如一个多边形的按钮,把一张图片切成邮票。

UIView:

layer.mask:

最终绘制:

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