UIView's shadowpath color doesn't change

问题

I have a UIView and I set a shadowPath for it like this:

func addShadow() {
    let cornerRadius: CGFloat = self.containerView.frame.height/2
    self.containerView.layer.shadowPath = UIBezierPath(roundedRect: self.containerView.frame, cornerRadius: cornerRadius).cgPath
    self.containerView.layer.shadowRadius = cornerRadius
    self.containerView.layer.shadowOffset = .zero
    self.containerView.layer.shadowOpacity = 0.2
    self.containerView.layer.cornerRadius = cornerRadius
    self.containerView.layer.shadowColor = UIColor(named: "whiteColor")?.cgColor
}

And this is whiteColor:

And now my problem is

When I change the appearance of the phone the shadowsPath color doesn't change automatically. What should I do to make the color dynamic?

回答1:

All layer properties don't react to color changes automatically (due to the conversion to CGColor).

Instead, react to trait collection changes and re-set the properties when the color appearance changes:

override open func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
    if #available(iOS 13, *), self.traitCollection.hasDifferentColorAppearance(comparedTo: previousTraitCollection) {
        // re-set your properties here
    }
}

回答2:

add self.view.layoutIfNeeded() in your function.It might solve your issue. In alternative way you will add color in viewDidLayoutSubviews.

回答3:

So this is what worked for me - it's a mix between Frank Schlegel's answer and between Kurt Revis's answer to the cgColor question

---

override open func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {

   if #available(iOS 13, *), self.traitCollection.hasDifferentColorAppearance(comparedTo: previousTraitCollection) {

       SubmissionOptionsMenu.layer.shadowColor = 
              UIColor.label.resolvedColor(with: self.traitCollection).cgColor
   }
}

来源：https://stackoverflow.com/questions/58092716/uiviews-shadowpath-color-doesnt-change