SwiftUI strange animation behaviour

Question

I have a very simple spinner animation on a page.

struct SmallSpinner: View {
    @State private var spinXSmall = false
    var body: some View {
        Circle() // X-Small
            .trim(from: 1 / 4, to: 1)
            .stroke(style: StrokeStyle(lineWidth: 1, lineCap: .round, lineJoin: .round))
            .foregroundColor(Color(#colorLiteral(red: 0.6588235294, green: 0.6588235294, blue: 0.6745098039, alpha: 1)))
            .frame(width: 12, height: 12)
            .rotationEffect(.degrees(spinXSmall ? 0 : 360))
            .scaleEffect(spinXSmall ? 1 : 0.8)
            .animation(Animation.easeOut(duration: 1).repeatForever(autoreverses: false))
            .onAppear {
                self.spinXSmall.toggle()
            }
    }
}

It looks strange and i don't know what's the root cause. see video below.

Make sure to pass in a ‘value’ for the ‘.animation’. Otherwise SwiftUI will animate it whenever the layout changes, causing weird position animations. — aheze
– aheze, Commented Aug 31, 2021 at 22:27
It is because of NavigationView! And there is no easy answer for it, I must see the all code, then maybe I can answer it! but the issue is not animation, I believe you have NavigationView, right? — swiftPunk
– swiftPunk, Commented Aug 31, 2021 at 23:13
@swiftPunk You are right, the problem is on NavigationView. Everything is perfect if i remove NavigationView. However, i do need that, is there any workaround? Thank — LiangWang
– LiangWang, Commented Aug 31, 2021 at 23:32
@LiangWang I recently answered a very similar question here - try using explicit withAnimation instead. And you might need to also use DispatchQueue.main.async {}, for mysterious reasons only known to Apple. — aheze
– aheze, Commented Aug 31, 2021 at 23:39
@LiangWang: I answered almost same question here: stackoverflow.com/a/68906529/14998134 but the issue could be deferent in your case, I must look to your code for better answer. — swiftPunk
– swiftPunk, Commented Aug 31, 2021 at 23:45

belal medhat · Accepted Answer · 2022-01-30 19:23:47Z

4

the issue happens due to an issue in NavigationView and it's not solved yet, so what you need to do is to add the toggle for spinXSmall in DispatchQueue and add a value to the animation Modifier and give it the spinXSmall

struct SmallSpinner: View {
@State private var spinXSmall = false
var body: some View {
    Circle() // X-Small
        .trim(from: 1 / 4, to: 1)
        .stroke(style: StrokeStyle(lineWidth: 1, lineCap: .round, lineJoin: .round))
        .foregroundColor(Color(#colorLiteral(red: 0.6588235294, green: 0.6588235294, blue: 0.6745098039, alpha: 1)))
        .frame(width: 12, height: 12)
        .rotationEffect(.degrees(spinXSmall ? 0 : 360))
        .scaleEffect(spinXSmall ? 1 : 0.8)
        .animation(Animation.easeOut(duration: 1).repeatForever(autoreverses: false),value:spinXSmall)
        .onAppear {
            DispatchQueue.main.async {
            self.spinXSmall.toggle()
        }
        }
   }
   }

answered Jan 30, 2022 at 19:23

belal medhat

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1 Comment

Dilan Over a year ago

iOS 17 also have the issue and this fix works perfectly.

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