阻止 CALayer 阴影影响子视图？

Question

我有一个自定义的UIControl，我想让它有一个影子，所以我在它的layer上设置了相关的属性。根据需要，视图周围会出现阴影，但是 UILabel 的文本下方也会出现阴影，这是一个子视图。你怎么阻止这个？我只想要外部超级视图周围的阴影。

...
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
    ...
}

Answer 1

当父视图的 alpha 小于 1.0 或没有背景颜色（即设置为透明颜色）时会发生这种情况。在这种情况下，阴影会转化为子视图。有关更多详细信息，请参阅我的回答 here。

Apple Docs 证明这一点：

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.

Answer 2

只需更改您的子视图父级即可。

换句话说，在透明阴影视图上方创建新的父视图，并将子视图插入到这个新的父视图中。

阻止 CALayer 阴影影响子视图？

Stop CALayer shadow from affecting subviews?

shadow

calayer

uiview

ios

ios8