SwiftUI 五彩纸屑动画

Question

注意：我解决了这个问题。如果您对动画感兴趣，我用 SPM 创建了一个包，可以在 https://github.com/simibac/ConfettiSwiftUI

上找到

所以我正在尝试在 SwiftUI 中创建五彩纸屑动画。这是我目前所拥有的：

这一切都按预期工作，并使用以下代码完成：

struct Movement{
    var x: CGFloat
    var y: CGFloat
    var z: CGFloat
    var opacity: Double
}

struct FancyButtonViewModel: View {
    @State var animate = [false]
    @State var finishedAnimationCouter = 0
    @State var counter = 0
    
    var body: some View {
        VStack{
            ZStack{
                ForEach(finishedAnimationCouter...counter, id:\.self){ i in
                    ConfettiContainer(animate:$animate[i], finishedAnimationCouter:$finishedAnimationCouter, num:1)
                }
            }
            
            Button("Confetti"){
                animate[counter].toggle()
                animate.append(false)
                counter+=1
            }
        }
    }
}

struct ConfettiContainer: View {
    @Binding var animate:Bool
    @Binding var finishedAnimationCouter:Int

    var num:Int
    
    var body: some View{
        ZStack{
            ForEach(0...num-1, id:\.self){ _ in
                Confetti(animate: $animate, finishedAnimationCouter:$finishedAnimationCouter)
            }
        }
        .onChange(of: animate){_ in
            DispatchQueue.main.asyncAfter(deadline: .now() + 3.5) {
                finishedAnimationCouter+=1
            }
        }
    }
}

struct Confetti: View{
    @Binding var animate:Bool
    @Binding var finishedAnimationCouter:Int
    @State var movement = Movement(x: 0, y: 0, z: 1, opacity: 0)
    

    var body: some View{
        Text("❤️")
            .frame(width: 50, height: 50, alignment: .center)
            .offset(x: movement.x, y: movement.y)
            .scaleEffect(movement.z)
            .opacity(movement.opacity)
            .onChange(of: animate) { _ in
                withAnimation(Animation.easeOut(duration: 0.4)) {
                    movement.opacity = 1
                    movement.x = CGFloat.random(in: -150...150)
                    movement.y = -300 * CGFloat.random(in: 0.7...1)
                }

                DispatchQueue.main.asyncAfter(deadline: .now() + 0.4) {
                    withAnimation(Animation.easeIn(duration: 3)) {
                        movement.y = 200
                        movement.opacity = 0.0
                    }
                }
        }
    }
}

现在我想用动画五彩纸屑视图替换心形表情符号。因此，我创建了以下视图：

struct ConfettiView: View {
    @State var animate = false
    @State var xSpeed = Double.random(in: 0.7...2)
    @State var zSpeed = Double.random(in: 1...2)
    @State var anchor = CGFloat.random(in: 0...1).rounded()
    
    var body: some View {
        Rectangle()
            .frame(width: 20, height: 20, alignment: .center)
            .onAppear(perform: { animate = true })
            .rotation3DEffect(.degrees(animate ? 360:0), axis: (x: 1, y: 0, z: 0))
            .animation(Animation.linear(duration: xSpeed).repeatForever(autoreverses: false))
            .rotation3DEffect(.degrees(animate ? 360:0), axis: (x: 0, y: 0, z: 1), anchor: UnitPoint(x: anchor, y: anchor))
            .animation(Animation.linear(duration: zSpeed).repeatForever(autoreverses: false))
    }
}

这也符合预期。但是，如果我将 Text("❤️") 替换为。 ConfettiView() 我得到了一些意想不到的动画，如下所示。（我将五彩纸屑的数量减少到 1，这样可以更好地观察动画）。动画中断了什么？

Answer 1

你的动画重叠，要解决你需要加入状态值的内部动画。

这里是固定变体。使用 Xcode 12.1 / iOS 14.1

测试

struct ConfettiView: View {
    @State var animate = false
    @State var xSpeed = Double.random(in: 0.7...2)
    @State var zSpeed = Double.random(in: 1...2)
    @State var anchor = CGFloat.random(in: 0...1).rounded()
    
    var body: some View {
        Rectangle()
            .frame(width: 20, height: 20, alignment: .center)
            .onAppear(perform: { animate = true })
            .rotation3DEffect(.degrees(animate ? 360:0), axis: (x: 1, y: 0, z: 0))
            .animation(Animation.linear(duration: xSpeed).repeatForever(autoreverses: false), value: animate)
            .rotation3DEffect(.degrees(animate ? 360:0), axis: (x: 0, y: 0, z: 1), anchor: UnitPoint(x: anchor, y: anchor))
            .animation(Animation.linear(duration: zSpeed).repeatForever(autoreverses: false), value: animate)
    }
}

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