为UIView设置阴影效果

阴影效果的实现,苹果提供了很好的实现方式,主要是layer层的绘制,具体的原理,可以查询资料.

1.最直接,也是比较简单的方式:效果如红色view

func addShadowView(){
        let shadowView = UIView(frame: CGRectMake(100, 100, 100, 100))
        shadowView.backgroundColor = UIColor.redColor()
        //setShadow
        shadowView.layer.cornerRadius = 5;
        shadowView.layer.shadowColor = UIColor.blackColor().CGColor
        shadowView.layer.shadowOffset = CGSizeMake(5, 10)
        shadowView.layer.shadowOpacity = 1.0
        shadowView.layer.shadowRadius = 5;
        //clipsToBounds为true不会显示阴影
        //shadowView.clipsToBounds = true
        view.addSubview(shadowView)
        
        
    }

 

2.可以自定义一个view,重写drawRect:方法

主要代码:

override func drawRect(rect: CGRect) {
        //get contextRef
        var context = UIGraphicsGetCurrentContext()
        //rect
        var pathRect = CGRectInset(self.bounds, self.bounds.size.width * 0.1, self.bounds.size.height * 0.1)
        let cornerRaidus: CGFloat = 20
        var rectanglePath = UIBezierPath(roundedRect: pathRect, cornerRadius: cornerRaidus)
        CGContextSaveGState(context)
        //set shadow
        var shadow = UIColor.blackColor().CGColor
        var shadowOffset = CGSizeMake(3, 3)
        var shadowRadius : CGFloat = 5.0
        
        
        CGContextSetShadowWithColor(context, shadowOffset, shadowRadius, shadow)
        //fill color
        UIColor.greenColor().setFill()
        rectanglePath.fill()
        CGContextRestoreGState(context)
    }

效果为绿色view

类似的渐变色,transform都重写drawRect:可以自己定义.