Ios swiftui动画如何实时确定不对称过渡

我试着用Toggle手动控制它是哪个过渡.如果我只切换了before切换方向，过渡就能正常工作.例如，向右转3次，切换，然后向左转3次.

当你用按钮自动做这件事时，看起来index次更改的时间与transition次更改的时间"太接近"了，而且没有我手动更改时的效果.

如果你只是将index的更改推迟一小段时间，它应该会起作用.

transition = ...
DispatchQueue.main.asyncAfter(deadline: .now() + 0.001) {
    index += 1 // or -= 1
}

有趣的是，DispatchQueue.main.async { ... }美元并不管用.你必须给它一些时间.

我还建议使用Bool或枚举来编码它要进入的方向，而不是AnyTransition.

工作代码:

@State var translations:[String] = ["Lorem Ipsum", "Foo Bar baz", "Something Else", "AAAAA", "BBBBB"]
@State var index = 0

@State var isForward = true

var body:some View{
    VStack {
        HStack{
            if(translations.count > 1){
                Button {
                    if(index > 0){
                        isForward = false
                        DispatchQueue.main.asyncAfter(deadline: .now() + 0.001) {
                            index -= 1
                        }
                    }
                } label: {
                    Image(systemName:"arrowtriangle.backward.circle.fill")
                }
                .disabled(index == 0)
            }
            
            if translations.count > 0 {
                Text(translations[index])
                    .font(.body)
                    .id(index)
                    .transition(
                        // I did not combine with .opacity here to make it more obvious
                        isForward ?
                            .asymmetric(insertion: .move(edge: .trailing), removal:.move(edge: .leading)) :
                                .asymmetric(insertion: .move(edge: .leading), removal:.move(edge: .trailing))
                    )
            }
            
            Spacer()
            
            if(translations.count  > 1){
                Button {
                    if index < translations.count - 1 {
                        isForward = true
                        DispatchQueue.main.asyncAfter(deadline: .now() + 0.001) {
                            index += 1
                        }
                    }
                } label: {
                    Image(systemName:"arrowtriangle.forward.circle.fill")
                }
                .disabled(index == translations.count - 1)
            }
        }
        .animation(.default,value: index)
    }
}