如何阻止 SwiftUI DragGesture 对子视图进行动画处理

Question

我正在构建一个自定义模态，当我拖动模态时，任何附加动画的子视图都会在我拖动时进行动画处理。我该如何阻止这种情况发生？

我考虑过传递@EnvironmentObject带有isDragging标志的 an ，但它的可扩展性不太好（并且不能很好地与自定义ButtonStyles 配合使用）

import SwiftUI

struct ContentView: View {
    var body: some View {
        Text("Hello, world!")
            .padding()
            .showModal(isShowing: .constant(true))
    }
}

extension View {
    func showModal(isShowing: Binding<Bool>) -> some View {
        ViewOverlay(isShowing: isShowing, presenting: { self })
    }
}

struct ViewOverlay<Presenting>: View where Presenting: View {
    @Binding var isShowing: Bool
    
    let presenting: () -> Presenting
    
    @State var bottomState: CGFloat = 0
    
    var body: some View {
        ZStack(alignment: .center) {
            presenting().blur(radius: isShowing ? 1 : 0)
            VStack {
                if isShowing {
                    Container()
                        .background(Color.red)
                        .offset(y: bottomState)
                        .gesture(
                            DragGesture()
                                .onChanged { value in
                                    bottomState = value.translation.height
                                }
                                .onEnded { _ in
                                    if bottomState > 50 {
                                        withAnimation {
                                            isShowing = false
                                        }
                                    }
                                    bottomState = 0
                                })
                        .transition(.move(edge: .bottom))
                }
            }
        }
    }
}

struct Container: View {
    var body: some View {
// I want this to not animate when dragging the modal
        Text("CONTAINER")
            .frame(maxWidth: .infinity, maxHeight: 200)
            .animation(.spring())
    }
}

更新：

extension View {
    func animationsDisabled(_ disabled: Bool) -> some View {
        transaction { (tx: inout Transaction) in
            tx.animation = tx.animation
            tx.disablesAnimations = disabled
        }
    }
}


Container()
   .animationsDisabled(isDragging || bottomState > 0)

在现实生活中，容器包含一个按钮，在按下状态下有动画

struct MyButtonStyle: ButtonStyle {
    func makeBody(configuration: Self.Configuration) -> some View {
        configuration.label
            .scaleEffect(configuration.isPressed ? 0.9 : 1)
            .animation(.spring())
    }
}

将animationsDisabled 函数添加到子视图中，该函数实际上会阻止子视图在拖动过程中移动。

它不会做的是当生物最初滑入或消失时停止动画。

有没有办法知道视图何时基本上没有移动/转换？

Answer 1

理论上，在这种情况下 SwiftUI 不应该翻译动画，但是我不确定这是否是一个错误 - 我不会以这种通用方式在 Container 中使用动画。我使用动画越多，就越倾向于将它们直接连接到特定值。

无论如何......这里有一个可能的解决方法 - 通过在中间注入不同的托管控制器来破坏动画可见性。

使用 Xcode 12 / iOS 14 进行测试

struct ViewOverlay<Presenting>: View where Presenting: View {
    @Binding var isShowing: Bool
    
    let presenting: () -> Presenting
    
    @State var bottomState: CGFloat = 0
    
    var body: some View {
        ZStack(alignment: .center) {
            presenting().blur(radius: isShowing ? 1 : 0)
            VStack {
                    Color.clear
                if isShowing {
                        HelperView {
                    Container()
                        .background(Color.red)
                        }
                        .offset(y: bottomState)
                        .gesture(
                             DragGesture()
                                  .onChanged { value in
                                        bottomState = value.translation.height
                                  }
                                  .onEnded { _ in
                                        if bottomState > 50 {
                                             withAnimation {
                                                  isShowing = false
                                             }
                                        }
                                        bottomState = 0
                                  })
                        .transition(.move(edge: .bottom))
                }
                    Color.clear
            }
        }
    }
}

struct HelperView<Content: View>: UIViewRepresentable {
    let content: () -> Content
    func makeUIView(context: Context) -> UIView {
        let controller = UIHostingController(rootView: content())
        return controller.view
    }
    
    func updateUIView(_ uiView: UIView, context: Context) {
    }
}