设置阴影

 //先边框

 bigView.layer.borderWidth = 0.3

 bigView.layer.borderColor = //UIColor.init(red: 170 /  255, green: 177 / 255, blue: 170 / 255, alpha: 1.0).cgColor

 UIColor.groupTableViewBackground.cgColor

 //中阴影

 bigView.layer.shadowColor = UIColor.init(red: 170 /  255, green: 177 / 255, blue:

170 / 255, alpha: 1.0).cgColor

 bigView.layer.shadowOpacity = 0.8//不透明度

 bigView.layer.shadowRadius = 5.0//设置阴影所照射的范围

 bigView.layer.shadowOffset = CGSize.init(width: 0, height: 0)// 设置阴影的偏移量

 

 //后设置圆角

 bigView.layer.cornerRadius = 5

 //bigView.clipsToBounds = true//设置为true，阴影失效