为什么在实际设备上的TabView上，用作aSwiftUI ZStack背景的`Color.`不会更新？

Question

此代码在画布预览上似乎可以很好地工作，但是在我的真实设备上，有时背景色不会更新。切换选项卡时，尽管其余视图很好，但仍保留前一个视图的颜色。有什么作用？

这是主选项卡视图：

import SwiftUI

struct ContentView: View {

    @EnvironmentObject var isModalVisible: CustomModal
    @ObservedObject var modal = CustomModal()

    var body: some View {

        ZStack {
            TabView {
                ZStack {
                Color.pink.opacity(0.2)
                        Button(action: {
                            withAnimation{
                                self.isModalVisible.isModalVisible.toggle()
                                self.modal.currentModal = VisibleModal.circle
                            }
                        }) {
                            Text("Circle").font(.headline)
                        }
                        .frame(width: 270, height: 64)
                        .background(Color.pink.opacity(0.5)).foregroundColor(.white)
                        .cornerRadius(12)
                }
                   .tabItem{
                       VStack{
                       Image(systemName: "1.square.fill")
                       Text("One")
                       }
                    }.tag(1)
                   ZStack {
                   Color.blue.opacity(0.2)
                       Button(action: {
                        self.isModalVisible.isModalVisible.toggle()
                        self.modal.currentModal = VisibleModal.squircle
                       }) {
                           Text("Squircle").font(.headline)
                       }
                       .frame(width: 270, height: 64)
                       .background(Color.blue.opacity(0.5)).foregroundColor(.white)
                       .cornerRadius(12)
                       }
                   .tabItem{
                          VStack{
                          Image(systemName: "2.square.fill")
                          Text("Two")
                          }
                       }.tag(2)
               }.accentColor(.purple)
            if self.isModalVisible.isModalVisible {
                VStack {
                    containedView().onAppear().transition(AnyTransition.scale.combined(with: .opacity).animation(.easeInOut(duration: 3.75)))

                }
            }
        }
    }

    func containedView() -> AnyView {
        switch modal.currentModal {
           case .circle: return AnyView(CircleView())
           case .squircle: return AnyView(SquircleView())
           case .none: return AnyView(Text(""))
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView().environmentObject(CustomModal())
    }
}

这是另一个具有子视图模态的文件：

import SwiftUI

class CustomModal: ObservableObject {
    @Published var isModalVisible = false
    @Published var currentModal: VisibleModal = .none
}

enum VisibleModal {
    case circle, squircle, none
}

struct CircleView: View {
    @EnvironmentObject var env: CustomModal

    var body: some View {
        ZStack {
            Color.pink.blur(radius: 0.4)
            Circle().fill()
            .frame(width: 300)
                .foregroundColor(Color.white.opacity(0.75))
            dismissButton()
        }.edgesIgnoringSafeArea(.all)
            .onAppear()
                .transition(AnyTransition.scale.combined(with: .opacity).animation(.easeInOut(duration: 3.75)))
    }
}

struct SquircleView: View {
    var body: some View {
        ZStack{
            Color.green.blur(radius: 0.4)
            RoundedRectangle(cornerRadius: 78, style: .continuous)
                .frame(width: 300, height: 300).foregroundColor(Color.white.opacity(0.75))
            dismissButton()
        }.edgesIgnoringSafeArea(.all)
    }
}

struct dismissButton: View {

    @EnvironmentObject var env: CustomModal

    var body: some View {
        VStack{
            Spacer()
            Button(action: {
                self.env.isModalVisible.toggle()
                print("TAPPED")
            }) {
                Text("Dismiss").font(.headline)
            }
            .frame(width: 270, height: 64)
            .background(Color.white.opacity(0.35)).foregroundColor(.white)
            .cornerRadius(12)
            .padding(.bottom, 44)
        }
    }
}

struct SecondFile_Previews: PreviewProvider {
    static var previews: some View {
        /*@START_MENU_TOKEN@*/Text("Hello, World!")/*@END_MENU_TOKEN@*/
    }
}

我的目标是使用enum从主视图中选择全屏模式视图。

我实际上有一个第二个问题：如何使动画与此相关？他们似乎没有。