UIView's shadowpath color doesn't change

Question

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 shadowPath's color doesn't change automatically. What should I do to make the color dynamic?

Do all your color stuff in layoutSubview or viewDidLayoutSubviews. Then you set the color to a dynamic variable that will compute it's value based on the traitCollection.userInterfaceStyle — andromedainiative, Sep 25 '19 at 07:04
@andromedainiative Are you sure it's the best way? I have many views that have shadow, Is it right that to set all of them in `layoutSubView`? — Arash Etemad, Sep 25 '19 at 07:07
I mean there is no silver bullet generic solution that I know of. We ended up moving all our color setup these methods. You can read more about it here. Unless you use the same view controller in every view you have you will have to do some updating of colors manually. https://developer.apple.com/documentation/appkit/supporting_dark_mode_in_your_interface — andromedainiative, Sep 26 '19 at 08:52

Frank Rupprecht · Accepted Answer · 2020-07-22T05:25:44.697

13

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?) {
    super.traitCollectionDidChange(previousTraitCollection)

    if #available(iOS 13, *), self.traitCollection.hasDifferentColorAppearance(comparedTo: previousTraitCollection) {
        // re-set your properties here
    }
}

edited Jul 22 '20 at 05:25

answered Sep 25 '19 at 07:10

Frank Rupprecht

9,191
31
56

Then I should override this method in every `ViewController`?! I need a more generic solution! – Arash Etemad Sep 25 '19 at 07:18
Only were you set layer properties. But yes, it's a pain. I created a `BaseView` that provides `UIColor` properties for all those layer properties and handles appearance changes. But now I ended up with 4 different `BaseView`s for buttons, table view cells, etc... – Frank Rupprecht Sep 25 '19 at 07:22
Please call super.traitCollectionDidChange – Umair Jul 21 '20 at 21:03

score 2 · Answer 2 · answered Nov 14 '19 at 02:10

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
   }
}

score 0 · Answer 3 · answered Sep 25 '19 at 07:20

0

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

answered Sep 25 '19 at 07:20

Nahid Raihan

957
1
10
20

`self.view.layoutIfNeeded()` didn't work, and I think overriding `viewDidLayoutSubViews` is not the best! cause I should override this method in every ViewController! I need a more generic solution! – Arash Etemad Sep 25 '19 at 07:28
The best generic solution I can think of is to create a base view class that handles trait changes and derive from that for all views that need it. – Frank Rupprecht Sep 25 '19 at 07:33
Can u run it in main thread ? its might be work . I mean using- func addShadow() { DispatchQueue.main.async { //your code here} } – Nahid Raihan Sep 25 '19 at 07:36
@NahidRaihan nothing happened! – Arash Etemad Sep 25 '19 at 07:41
1.from where did you call this function ? 2. Add self.view.layoutIfNeeded() starting line in method and add again in before ending . – Nahid Raihan Sep 25 '19 at 07:45
add it in ```viewWillAppear() ``` please. – Nahid Raihan Sep 25 '19 at 07:56

UIView's shadowpath color doesn't change

3 Answers3