SwiftUI Custom View repeat forever animation show as unexpected - swift

Question

I created a custom LoadingView as a Indicator for loading objects from internet. When add it to NavigationView, it shows like this
enter image description here
I only want it showing in the middle of screen rather than move from top left corner
Here is my Code
struct LoadingView: View {
#State private var isLoading = false
var body: some View {
Circle()
.trim(from: 0, to: 0.8)
.stroke(Color.primaryDota, lineWidth: 5)
.frame(width: 30, height: 30)
.rotationEffect(Angle(degrees: isLoading ? 360 : 0))
.onAppear {
withAnimation(.linear(duration: 1).repeatForever(autoreverses: false)) {
self.isLoading.toggle()
}
}
}
}
and my content view
struct ContentView: View {
var body: some View {
NavigationView {
LoadingView()
.frame(width: 30, height: 30)
}
}
}

Answer 1

This looks like a bug of NavigationView: without it animation works totally fine. And it wan't fixed in iOS15.
Working solution is waiting one layout cycle using DispatchQueue.main.async before string animation:
struct LoadingView: View {
#State private var isLoading = false
var body: some View {
Circle()
.trim(from: 0, to: 0.8)
.stroke(Color.red, lineWidth: 5)
.frame(width: 30, height: 30)
.rotationEffect(Angle(degrees: isLoading ? 360 : 0))
.onAppear {
DispatchQueue.main.async {
withAnimation(.linear(duration: 1).repeatForever(autoreverses: false)) {
self.isLoading.toggle()
}
}
}
}
}

Answer 2

This is a bug from NavigationView, I tried to kill all possible animation but NavigationView ignored all my try, NavigationView add an internal animation to children! here all we can do right now!
struct ContentView: View {
var body: some View {
NavigationView {
LoadingView()
}
}
}
struct LoadingView: View {
#State private var isLoading: Bool = Bool()
var body: some View {
Circle()
.trim(from: 0, to: 0.8)
.stroke(Color.blue, lineWidth: 5.0)
.frame(width: 30, height: 30)
.rotationEffect(Angle(degrees: isLoading ? 360 : 0))
.animation(Animation.linear(duration: 1).repeatForever(autoreverses: false), value: isLoading)
.onAppear { DispatchQueue.main.async { isLoading.toggle() } }
}
}