ios – 停止CALayer影子影响子视图？

我有一个定制的UIControl,我希望它有一个阴影,所以我设置相关属性在它的图层.在视图周围出现阴影,但阴影也会出现在UILabel的文本下,该文本是子视图.你如何阻止这个？我只想要外部超级视野的影子.

...
init() {        
    label = UILabel()
    label.translatesAutoresizingMaskIntoConstraints = false
    self.translatesAutoresizingMaskIntoConstraints = false
    addSubview(label)

    self.layer.masksToBounds = false
    self.layer.shadowColor = UIColor.blackColor().CGColor
    self.layer.shadowOpacity = 1.0
    self.layer.shadowRadius = 2.0

    // Adding these lines trying to explicitly stop shadow on label...
    label.layer.shadowOpacity = 0
    label.layer.shadowColor = nil
    ...
}

解决方法

当父视图的alpha值小于1.0或没有背景颜色(即设置为清除颜色)时,会发生这种情况.在这种情况下,阴影转换为子视图.有关详细信息,请参阅我的答案 here.

苹果Docs证明了这一点：

figure A-7 shows several different versions of the same sample layer with a red shadow applied. The left and middle versions include a background color so the shadow appears only around the border of the layer. However,the version on the right does not include a background color. In this case,the shadow is applied to the layer’s content,border,and sublayers.