为UIView设置阴影效果

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.

注意一定不要写，否则不会显示阴影

self.view.layer.masksToBounds = YES;
或者
self.view.layer.clipsToBounds = YES;

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.