在Xcode 12的SwiftUI项目中使用ViewRouter

我试图在新的Xcode 12项目中使用此方法（请参阅附件）作为创建SwiftUI应用程序登录页面的方法，但是我遇到了一个问题，即不知道要向主App结构中添加什么。我仍然是一个初学者，并尝试将其添加ContentView().environmentObject(ViewRouter())到主应用程序结构中的WindowGroup中。我是完全错误的还是Xcode为什么不建立视图？有人可以帮忙吗？在工作代码段下方：

import SwiftUI
import Foundation
import Combine

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?


    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView: MotherView().environmentObject(ViewRouter()))
            self.window = window
            window.makeKeyAndVisible()
        }
    }
. . .
}

class ViewRouter: ObservableObject {
    let objectWillChange = PassthroughSubject<ViewRouter,Never>()
    var currentPage: String = "page1" {
        didSet {
            withAnimation() {
                objectWillChange.send(self)
            }
        }
    }
}

struct MotherView : View {
    @EnvironmentObject var viewRouter: ViewRouter
    var body: some View {
        VStack {
            if viewRouter.currentPage == "page1" {
                ContentViewA()
            } else if viewRouter.currentPage == "page2" {
                ContentViewB()
                    .transition(.scale)
            }
        }
    }
}

struct ContentViewA : View {
    @EnvironmentObject var viewRouter: ViewRouter
    var body: some View {
        Button(action: {self.viewRouter.currentPage = "page2"}) {
            Text("Login")
        }
    }
}

struct ContentViewB : View {
    
    @EnvironmentObject var viewRouter: ViewRouter
    
    var body: some View {
        Button(action: {self.viewRouter.currentPage = "page1"}) {
            Text("Logout")
        }
    }
}

现在，我想用Xcode 12样式替换SceneDelegate，但是以下方法不起作用。知道为什么吗？

@main
struct TestApp: App {
    var body: some Scene {
        WindowGroup {
            MotherView().environmentObject(ViewRouter())
        }
    }
}