self.shadowView.layer.shadowOpacity = 0.6;// 阴影透明度
self.shadowView.layer.shadowColor = [UIColor darkGrayColor].CGColor;// 阴影的颜色
self.shadowView.layer.shadowRadius = 2;// 阴影扩散的范围控制
self.shadowView.layer.shadowOffset = CGSizeMake(1, 1);// 阴影的范围原文：https://www.cnblogs.com/guligei/p/9473840.html