ios - 如果两个 View 相同，为什么 TabView 显示空白屏幕？

Question

我的应用程序中有一个 TabView，用于显示四个屏幕。两者相似但具有不同的数据源。如果我单击第一个选项卡 (EventsScreen)，然后单击第三个选项卡 (MyBagScreen)，则一切正常。如果我单击第一个选项卡 (EventsScreen)，然后单击第二个选项卡 (EventsScreen)，它只会加载一个空白屏幕(我认为它只是加载背景)。它们是两个不同的对象，为什么这不起作用？

AppView.swift

struct AppView: View {
    var body: some View {
        TabView {
            EventsScreen().environmentObject(EventsViewModel(repo: IncentivesRespository()))
                .tabItem {
                    Text("Barter")
                    Image("icon_barter")
            }
            EventsScreen().environmentObject(EventsViewModel(repo: OpportunityRepository()))
                .tabItem {
                    Text("Earn")
                    Image("icon_earn")
            }
            MyBagScreen().environmentObject(MyBagViewModel())
                .tabItem{
                    Text("My Bag")
                    Image("icon_bag")
            }
            AccountScreen().environmentObject(AccountViewModel())
                .tabItem {
                    Text("Account")
                    Image("icon_account")

            }
        }
        .onAppear(perform: {
            UITabBar.appearance().backgroundColor = .black
        })
            .navigationBarHidden(true)
    }
}

事件屏幕

struct EventsScreen: View {

    @EnvironmentObject
    var viewModel: EventsViewModel

    let calendarManager = RKManager(calendar: Calendar.current, minimumDate: Date(), maximumDate: Date().addingTimeInterval(60*60*24*90), mode: 1)

    @State
    var currentPage: Int = 0
    @State
    private var searchTerm : String = ""

    init() {
        UITableView.appearance().separatorStyle = .none
    }

    var body: some View {
        GeometryReader { geometry in
            List {
                ZStack(alignment: .top) {
                    EventViewController(controllers: self.viewModel.featureEventControllers, currentPage: self.$currentPage)
                    VStack {
                        SearchBar(text: self.$searchTerm)
                            .padding(EdgeInsets.init(top: 16, leading: 16, bottom: 0, trailing: 16))
                        HStack {
                            Spacer()
                            Chip(text: "Dates", action:  {
                                self.viewModel.showDateSelection.toggle()
                            })
                                .sheet(isPresented: self.$viewModel.showDateSelection, onDismiss: {
                                    self.viewModel.onDatesSelected(startDate: self.calendarManager.startDate, endDate: self.calendarManager.endDate)
                                }, content: {
                                    RKViewController(isPresented: self.$viewModel.showDateSelection, rkManager: self.calendarManager)
                                })
                            Chip(text:"Type", action: {
                                self.viewModel.showTypeSelection.toggle()
                            })
                            Chip(text: "Points", action: {
                                self.viewModel.showPointsSelection.toggle()
                            })
                            Spacer()
                        }
                    }
                }.listRowInsets(EdgeInsets())
                    .frame(height: 600)
                ForEach(self.viewModel.eventSections.indices) { id in
                    EventSectionView(eventSection: self.viewModel.eventSections[id])
                }
                .listRowBackground(Color.black)
            }
            .navigationBarTitle(Text("Events"), displayMode: .inline)
            .navigationBarHidden(true)
            if self.viewModel.showPointsSelection {
                EventsPointsRangeBottomSheet(isOpen: self.$viewModel.showPointsSelection, selectedRange: self.$viewModel.selectedRange, range: 0.0...self.viewModel.maxPoints, action: {
                    self.viewModel.onPointsSelected()
                })

            }
            if self.viewModel.showTypeSelection {
                TypeBottomSheet(categories: self.viewModel.allCategories, isOpen: self.$viewModel.showTypeSelection, selectedCategoryUuids: self.$viewModel.selectedCategoryUuids, action: {
                    self.viewModel.onTypesSelected()
                })
            }

        }
    }
}

Answer 1

你的代码快照是不可测试的，所以只是一个想法——你必须自己测试它。

因此，假设您的第二个 View 的环境对象是正确的，请尝试使用 .id 使这些 View 真正独特。修饰符，如下

TabView {
    EventsScreen().environmentObject(EventsViewModel(repo: IncentivesRespository()))
        .id(1)                    // << here !!
        .tabItem {
            Text("Barter")
            Image("icon_barter")
    }
    EventsScreen().environmentObject(EventsViewModel(repo: OpportunityRepository()))
        .id(2)                    // << here !!
        .tabItem {
            Text("Earn")
            Image("icon_earn")
    }
    ...

注:我看到用法 .navigationBarHidden(true)在 AppView - 如果这意味着您要包含 TabView进入 NavigationView ，然后 不要那样做 - 你不会让它工作的。 TabView 被设计为 仅根 View .如果您需要导航，请将其放置在选项卡内。