iOS开发 给同一个view设置四个不同的圆角

1.圆角性能优化

在APP开发中，圆角图片还是经常出现的。如果一个界面中只有少量圆角图片或许对性能没有非常大的影响，但是当圆角图片比较多的时候就会APP性能产生明显的影响。我们设置圆角一般通过如下方式:

imageView.layer.cornerRadius=CGFloat(10);

imageView.layer.masks ToBounds=YES;

这样处理的渲染机制是GPU在当前屏幕缓冲区外新开辟一个 渲染缓冲区进行工作，也就是离屏渲染，这会给我们带来额外的性能损耗，如果这样的圆角操作达到一-定数量， 会触发 缓冲区的频繁合并和上下文的的频繁切换，性能的代价会宏观地表现在用户体验上一一掉帧。

优化方案:使用贝塞尔曲线UIBezierPath和Core Graphics框架画出一个圆角

extension UIView {
    
    /// BezierPath 圆角设置
    func roundCorners(_ corners: UIRectCorner = .allCorners, radius: CGFloat) {
        let maskPath = UIBezierPath(
            roundedRect: bounds,
            byRoundingCorners: corners,
            cornerRadii: CGSize( radius, height: radius))
        
        let shape = CAShapeLayer()
        shape.path = maskPath.cgPath
        layer.mask = shape
    }
}

2.设置不同大小的圆角

iOS开发中偶尔也能遇到需要设置不同大小圆角的需求，那么就需要绘制path来实现，具体代码如下

extension UIView {
    //添加4个不同大小的圆角
    func addCorner(cornerRadii:CornerRadii){
       let path = createPathWithRoundedRect(bounds: self.bounds, cornerRadii:cornerRadii)
       let shapLayer = CAShapeLayer()
       shapLayer.frame = self.bounds
       shapLayer.path = path
       self.layer.mask = shapLayer
    }
    //各圆角大小
    struct CornerRadii {
        var topLeft :CGFloat = 0
        var topRight :CGFloat = 0
        var bottomLeft :CGFloat = 0
        var bottomRight :CGFloat = 0
    }
    //切圆角函数绘制线条
    func createPathWithRoundedRect( bounds:CGRect,cornerRadii:CornerRadii) -> CGPath
    {
        let minX = bounds.minX
        let minY = bounds.minY
        let maxX = bounds.maxX
        let maxY = bounds.maxY
        
        //获取四个圆心
        let topLeftCenterX = minX +  cornerRadii.topLeft
        let topLeftCenterY = minY + cornerRadii.topLeft
         
        let topRightCenterX = maxX - cornerRadii.topRight
        let topRightCenterY = minY + cornerRadii.topRight
        
        let bottomLeftCenterX = minX +  cornerRadii.bottomLeft
        let bottomLeftCenterY = maxY - cornerRadii.bottomLeft
         
        let bottomRightCenterX = maxX -  cornerRadii.bottomRight
        let bottomRightCenterY = maxY - cornerRadii.bottomRight
        
        //虽然顺时针参数是YES，在iOS中的UIView中，这里实际是逆时针
        let path :CGMutablePath = CGMutablePath();
         //顶 左
        path.addArc(center: CGPoint(x: topLeftCenterX, y: topLeftCenterY), radius: cornerRadii.topLeft, startAngle: CGFloat.pi, endAngle: CGFloat.pi * 3 / 2, clockwise: false)
        //顶右
        path.addArc(center: CGPoint(x: topRightCenterX, y: topRightCenterY), radius: cornerRadii.topRight, startAngle: CGFloat.pi * 3 / 2, endAngle: 0, clockwise: false)
        //底右
        path.addArc(center: CGPoint(x: bottomRightCenterX, y: bottomRightCenterY), radius: cornerRadii.bottomRight, startAngle: 0, endAngle: CGFloat.pi / 2, clockwise: false)
        //底左
        path.addArc(center: CGPoint(x: bottomLeftCenterX, y: bottomLeftCenterY), radius: cornerRadii.bottomLeft, startAngle: CGFloat.pi / 2, endAngle: CGFloat.pi, clockwise: false)
        path.closeSubpath();
         return path;
    }
}