Repeating animation on SwiftUI Image

问题

Given the following struct:

struct PeopleList : View {
    @State var angle: Double = 0.0
    @State var isAnimating = true

    var foreverAnimation: Animation {
        Animation.linear(duration: 2.0)
            .repeatForever()
    }

    var body: some View {
        Button(action: {}, label: {
            Image(systemName: "arrow.2.circlepath")
                .rotationEffect(Angle(degrees: self.isAnimating ? self.angle : 0.0))
                .onAppear {
                    withAnimation(self.foreverAnimation) {
                        self.angle += 10.0
                    }
                }
        })
    }
}

I was hoping that the Image would rotate clockwise and repeat until self.isAnimating is false although it's only animated once.

回答1:

Here is possible solution for continuous progressing on appear & start/stop. Tested with Xcode 11.4 / iOS 13.4.

struct PeopleList : View {
    @State private var isAnimating = false
    @State private var showProgress = false
    var foreverAnimation: Animation {
        Animation.linear(duration: 2.0)
            .repeatForever(autoreverses: false)
    }

    var body: some View {
        Button(action: { self.showProgress.toggle() }, label: {
            if showProgress {
                Image(systemName: "arrow.2.circlepath")
                    .rotationEffect(Angle(degrees: self.isAnimating ? 360 : 0.0))
                    .animation(self.isAnimating ? foreverAnimation : .default)
                    .onAppear { self.isAnimating = true }
                    .onDisappear { self.isAnimating = false }
            } else {
                Image(systemName: "arrow.2.circlepath")
            }
        })
        .onAppear { self.showProgress = true }
    }
}

回答2:

UPDATE: There is a backspin involved while stopping the animation which is solved with this solution.

I think its this what you are looking for:

struct PeopleList : View {
    @State var angle: Double = 0.0
    @State var isAnimating = false
    
    var foreverAnimation: Animation {
        Animation.linear(duration: 2.0)
            .repeatForever(autoreverses: false)
    }
    
    var body: some View {
        Button(action: {}, label: {
            Image(systemName: "arrow.2.circlepath")
                .rotationEffect(Angle(degrees: self.isAnimating ? 360.0 : 0.0))
                .animation(self.foreverAnimation)
                .onAppear {
                    self.isAnimating = true
            }
        })
    }
}

来源：https://stackoverflow.com/questions/58315628/repeating-animation-on-swiftui-image

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swift

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swiftui