SOLVED: Instantly reset state of animation.

@PointOfNilReturn

Oct '20

Given a view like this:

struct ContentView: View {
    @State private var percentAnimated: CGFloat = .zero

    var body: some View {
        VStack {
            Button("Reset") {
                percentAnimated = .zero
            }

            AnimatedView() {
                // does something with percentAnimated
            }
            .onAppear {
                percentAnimated = 1
            }
        }
    }
}

When the view appears, percentAnimated's state changes to 1 and any animation in body that uses this state begins animating. When I tap the button, the state reverts back to zero but the animations that use this state 'reverse' their animations.

Is there a way to instantly set the state back to zero and bring any view that uses this state back to it's original state? (i.e. don't 'reverse' the animation, start over)

@roosterboy HWS+

Oct '20

First, you can't attach onAppear to the body property; you have to attach it to something inside the body property.

Then try adjusting the id of the View component to get everything back to the starting value. Something like this:

struct ResetRect: View {
    @State private var sz: CGFloat = 80
    var body: some View {
        Rectangle().frame(width: sz, height: sz)
            .onAppear {
                withAnimation(Animation.easeInOut(duration: 2.5).repeatForever(autoreverses: true)) {
                    sz *= 2
                }
            }
    }
}

struct ContentView: View {
    @State private var percentAnimated: CGFloat = .zero
    @State private var viewID = 0

    var body: some View {
        ResetRect()
            .id(viewID)
        Button("Reset") {
            viewID += 1
        }
        //...
        .onAppear {
            percentAnimated = 1
        }

    }

}

Changing the id resets everything because it is technically creating a brand new View struct to replace the existing one rather than resetting it to the initial values.

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