SwiftUI - 当用户打开推送通知时打开特定视图

Question

有一个用 SwiftUI 制作的应用，Parse 用于 DB。 我在应用程序的某些部分集成了一些发送通知的云功能（例如：当有人向您发送消息时，您将收到由该云功能触发的推送通知）。 在过去的日子里，当您按下通知打开应用程序时，我一直在努力寻找如何打开特定视图。 我找到了一些解决方案，但无法让它们发挥作用。

这是我到目前为止的代码：

class AppDelegate: NSObject, UIApplicationDelegate, UNUserNotificationCenterDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -> Bool {
        
        //Parse Intialization
        ...
        //notifications
        registerForPushNotifications()
        //Notification Badge
        UIApplication.shared.applicationIconBadgeNumber = 0
        // start notification while app is in Foreground
        UNUserNotificationCenter.current().delegate = self
        return true
    }
    
    // This function will be called right after user tap on the notification
    func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {
        print("app opened from PushNotification tap")
        UIApplication.shared.applicationIconBadgeNumber = 0
      completionHandler()
    }
}

@main
struct MyApp: App {
    
    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate
    
    var body: some Scene {
        WindowGroup {
            ContentView(currentTab: Tab.home)
        }
    }
}

应用程序打印“从 PushNotification 点击​​打开应用程序”，但如果我在 AppDelegate 中放置一个变量，并使用 .onReceive 或 .onChange 监听 Co​​ntentView 中的变化，则什么都不会发生

struct ContentView: View {
    @ObservedObject var appState = AppState()
    @State var currentTab : Tab
    @State var noReloadAddItemView = false
    var body: some View {
        TabView(selection: $appState.currentTab) {
            
            NavigationView {
                HomeView(appState: appState, noReloadAddItemView: $noReloadAddItemView)
                
            }
            .tabItem {
                if appState.currentTab == .home {
                    Image(systemName: "house.fill")
                } else {
                    Image(systemName: "house")
                }
                
                Text(LocalizedStringKey("HomeTabMenu"))
                
            }.tag(Tab.home)
            
            NavigationView {
                SearchView(appState: appState, noReloadAddItemView: $noReloadAddItemView)
            }
            .tabItem {
                if appState.currentTab == .search {
                    Image(systemName: "magnifyingglass.circle.fill")
                } else {
                    Image(systemName: "magnifyingglass")
                }
                Text(LocalizedStringKey("SearchTabMenu"))
            }.tag(Tab.search)
            
            NavigationView {
                AddItemView(appState: appState, noReloadAddItemView: $noReloadAddItemView)
            }
            .tabItem {
                if appState.currentTab == .add {
                    Image(systemName: "plus.circle.fill")
                } else {
                    Image(systemName: "plus.circle")
                }
                Text(LocalizedStringKey("SellTabMenu"))
            }.tag(Tab.add)
            
            NavigationView {
                ShoppingCartFavoritesView(appState: appState, noReloadAddItemView: $noReloadAddItemView)
            }
            .tabItem {
                if appState.currentTab == .favorites {
                    Image(systemName: "cart.fill")
                } else {
                    Image(systemName: "cart")
                }
                Text(LocalizedStringKey("CartTabMenu"))
            }.tag(Tab.favorites)
            
            NavigationView {
                ProfileView(appState: appState, noReloadAddItemView: $noReloadAddItemView)
            }
            .tabItem {
                if appState.currentTab == .profile {
                    Image(systemName: "person.fill")
                } else {
                    Image(systemName: "person")
                }
                Text(LocalizedStringKey("ProfileTabMenu"))
            }.tag(Tab.profile)
        }
        .accentColor(Color("ColorMainDark"))
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView(currentTab: Tab.home)
    }
}

class AppState: ObservableObject {
    @Published var currentTab : Tab = .home
}

enum Tab {
    case home, search, add, favorites, profile
}

Answer 1

您需要某种可以修改的共享状态，SwiftUI 知道它会做出反应。 ObservableObject 非常适合：

class AppState: ObservableObject {
    static let shared = AppState()
    @Published var pageToNavigationTo : String?
}

然后，要收听并响应它，您可以在主视图中执行几种不同的方法。

选项 1——基于 ObservedObject 值的 NavigationLink 绑定：

struct ContentView : View {
    @ObservedObject var appState = AppState.shared //<-- note this
    @State var navigate = false
    
    var pushNavigationBinding : Binding<Bool> {
        .init { () -> Bool in
            appState.pageToNavigationTo != nil
        } set: { (newValue) in
            if !newValue { appState.pageToNavigationTo = nil }
        }
    }
    
    var body: some View {
        NavigationView {
            Text("My content")
                .overlay(NavigationLink(destination: Dest(message: appState.pageToNavigationTo ?? ""),
                                        isActive: pushNavigationBinding) {
                    EmptyView()
                })
        }
    }
}

struct Dest : View {
    var message : String
    var body: some View {
        Text("\(message)")
    }
}

或者，您可以使用onReceive：

struct ContentView : View {
    @ObservedObject var appState = AppState.shared
    @State var navigate = false
    
    var body: some View {
        NavigationView {
            VStack {
                if navigate {
                    NavigationLink(destination: Text("Test"), isActive: $navigate ) {
                        EmptyView()
                    }
                }
                Text("My content")
                    .onReceive(appState.$pageToNavigationTo) { (nav) in
                        if nav != nil { navigate = true }
                    }
            }
        }
    }
}

我会将您的特定 NavigationView、NavigationLink、TabView 等的实现细节留给您，但这应该可以帮助您入门。

最后，一个模拟通知并展示导航视图的全功能最小示例：

class AppDelegate: NSObject, UIApplicationDelegate, UNUserNotificationCenterDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -> Bool {
     
        DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
            print("Dispatch")
            AppState.shared.pageToNavigationTo = "test"
        }
        
        return true
    }
}

class AppState: ObservableObject {
    static let shared = AppState()
    @Published var pageToNavigationTo : String?
}

@main
struct MultiWindowApp: App {
    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate

    
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

struct ContentView : View {
    @ObservedObject var appState = AppState.shared
    @State var navigate = false
    
    var pushNavigationBinding : Binding<Bool> {
        .init { () -> Bool in
            appState.pageToNavigationTo != nil
        } set: { (newValue) in
            if !newValue { appState.pageToNavigationTo = nil }
        }
    }
    
    var body: some View {
        NavigationView {
            Text("My content")
                .overlay(NavigationLink(destination: Dest(message: appState.pageToNavigationTo ?? ""),
                                        isActive: pushNavigationBinding) {
                    EmptyView()
                })
        }
    }
}


struct Dest : View {
    var message : String
    var body: some View {
        Text("\(message)")
    }
}