Swift withAnimation 动画完成监听

在ios17中withAnimation有completion方法可以监听动画完成，但是低于ios17没有，需要自定义一个监听器，原理就是通过AnimatableModifier可以监听到值的didSet修改，我们就可以调用回调函数。

代码

// 动画完成监听
struct AnimatableCompletionModifier<Value>: AnimatableModifier where Value: VectorArithmetic {var animatableData: Value {didSet {notifyCompletionIfFinished()}}private var targetValue: Valueprivate var completion: () -> Voidinit(observedValue: Value, completion: @escaping () -> Void) {self.completion = completionanimatableData = observedValuetargetValue = observedValue}private func notifyCompletionIfFinished() {guard animatableData == targetValue else { return }DispatchQueue.main.async {self.completion()}}func body(content: Content) -> some View {return content}
}extension View {func onAnimationCompleted<Value: VectorArithmetic>(for value: Value, completion: @escaping () -> Void) -> ModifiedContent<Self, AnimatableCompletionModifier<Value>> {modifier(AnimatableCompletionModifier(observedValue: value, completion: completion))}
}

使用

Text("回调").opacity(introTextOpacity).onAnimationCompleted(for: introTextOpacity) {print("成功回调了")}