iOS 17更新后EaseInOut动画无法正常工作问题求助

我写了一个Blink ViewModifier，在iOS 16里能持续平滑地淡入淡出，但升级到iOS 17后，动画只跑几次就停了。

相关代码：

struct Blink: ViewModifier {

@State private var opacity = 0.0

var isActive: Bool

func body(content: Content) -> some View {
    if isActive {
        content
            .opacity(self.opacity)
            .animation(.easeInOut(duration: 0.5)
                .repeatCount(1)
                .repeatForever(autoreverses: true),
                       value: self.opacity)
            .onAppear {
                DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
                    self.opacity = 1
                }
            }.onChange(of: opacity) {
              print(opacity)
            }
    }
    else {
        content
    }
    
}
}

iOS 17下的动画效果：

问题根源 #

iOS 17对SwiftUI动画的重复逻辑做了调整，原代码里同时用.repeatCount(1)和.repeatForever(autoreverses: true)会造成动画系统冲突。再加上只靠一次opacity值变更触发动画，iOS 17的动画优化机制会判定动画已完成，直接终止循环。

修复方案 #

方案1：清理重复配置，简化动画触发 #

删掉多余的.repeatCount(1)，让永久重复的动画逻辑正常生效：

struct Blink: ViewModifier {
    @State private var opacity = 0.0
    var isActive: Bool

    func body(content: Content) -> some View {
        Group {
            if isActive {
                content
                    .opacity(opacity)
                    .animation(
                        .easeInOut(duration: 0.5)
                            .repeatForever(autoreverses: true),
                        value: opacity
                    )
                    .onAppear {
                        // 保留原有的延迟触发，按需调整或直接移除延迟
                        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
                            opacity = 1
                        }
                    }
            } else {
                content
            }
        }
    }
}

方案2：用Timer主动控制动画状态（更稳定） #

如果方案1还是有问题，用Timer周期性切换opacity值，确保动画持续触发：

struct Blink: ViewModifier {
    @State private var opacity = 0.0
    @State private var timer: Timer?
    var isActive: Bool
    let animationDuration: Double = 0.5

    func body(content: Content) -> some View {
        Group {
            if isActive {
                content
                    .opacity(opacity)
                    .animation(.easeInOut(duration: animationDuration), value: opacity)
                    .onAppear {
                        startBlinkTimer()
                    }
                    .onDisappear {
                        timer?.invalidate()
                    }
                    .onChange(of: isActive) { newValue in
                        if newValue {
                            startBlinkTimer()
                        } else {
                            timer?.invalidate()
                            opacity = 0 // 重置透明度
                        }
                    }
            } else {
                content
            }
        }
    }

    private func startBlinkTimer() {
        timer?.invalidate()
        // 动画往返一次的时间是duration*2
        timer = Timer.scheduledTimer(withTimeInterval: animationDuration * 2, repeats: true) { _ in
            opacity = opacity == 0 ? 1 : 0
        }
        // 初始延迟触发一次，和原逻辑保持一致
        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
            opacity = 1
        }
    }
}

方案3：用AnimatableModifier自定义动画（精准控制） #

如果需要更底层的动画控制，实现AnimatableModifier：

struct Blink: AnimatableModifier {
    var isActive: Bool
    private var progress: Double = 0

    var animatableData: Double {
        get { progress }
        set { progress = newValue }
    }

    func body(content: Content) -> some View {
        content
            .opacity(isActive ? sin(progress * .pi) : 1)
            .onAppear {
                guard isActive else { return }
                withAnimation(.easeInOut(duration: 0.5).repeatForever(autoreverses: false)) {
                    progress = .infinity
                }
            }
            .onChange(of: isActive) { newValue in
                guard newValue else {
                    progress = 0
                    return
                }
                withAnimation(.easeInOut(duration: 0.5).repeatForever(autoreverses: false)) {
                    progress = .infinity
                }
            }
    }
}

内容的提问来源于stack exchange，提问作者Mohamed Said