iOS |无法在应用程序委托中更改根视图控制器 [英] IOS | Unable to change root view controller in app delegate

问题描述

我正在构建一个应用程序，如果用户登录，则必须更改其根视图控制器.说如果用户登录，则我必须在用户未登录的情况下将标签栏控制器显示为主屏幕，我必须显示身份验证控制器.我的两个控制器都是情节提要控制器.现在在我的应用程序委托中，我输入了以下代码

I am building an app whose root view controller must be changed if the user is logged in. Say if the user is logged in I must show a tab bar controller as the home screen if the user is not logged in, I must show an Authentication controller. Both my controllers are storyboard controllers. Now in my app delegate, I have put the following code

        window = UIWindow(frame: UIScreen.main.bounds)

        if UserDefaults.standard.bool(forKey: Constants.UserDefaultsKeys.isLoggedIn){
            initialViewController = storyboard.instantiateViewController(identifier: Constants.StoryBoards.homeViewController) as! TabController
        }else{
            initialViewController = storyboard.instantiateViewController(identifier: Constants.StoryBoards.authenticationController)
        }
        window?.rootViewController = initialViewController
        window?.makeKeyAndVisible()

根据代码，如果用户已登录，则必须显示TabController，但未显示.我尝试调试并调用了TabController的viewDidLoad，但仍然是我的authenticationController正在显示，这可能是因为authenticationController被设置为情节提要中的初始viewcontroller.有人可以帮我弄清楚这个问题吗

As per the code if the user is logged in ,TabController must be showed.But it is not being shown.I have tried debugging and TabController's viewDidLoad is being called but still my authenticationController is being shown and that is probably because authenticationController is set as the initial viewcontroller in the storyboard. Can someone help me figure out the issue

推荐答案

如果仅定位iOS 13+，则唯一需要做的更改就是添加一行:

If you are targeting only iOS 13+, the only change you should need to make is to add one line:

    window?.rootViewController = initialViewController

    // add this line
    self.window = window

    window?.makeKeyAndVisible()

如果您想支持早期的iOS版本，下面是一个完整的SceneDelegate/AppDelegate实施:

If you want to support earlier iOS versions, here is a complete SceneDelegate / AppDelegate implementation:

SceneDelegate.swift

//
//  SceneDelegate.swift
//  Created by Don Mag on 3/27/20.
//

import UIKit

// entire class is iOS 13+
@available(iOS 13.0, *)
class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {

        print("Scene Delegate willConnectTo", UserDefaults.standard.bool(forKey: "isLoggedIn"))

        guard let windowScene = (scene as? UIWindowScene) else { return }
        let window = UIWindow(frame: windowScene.coordinateSpace.bounds)
        window.windowScene = windowScene

        if UserDefaults.standard.bool(forKey: "isLoggedIn") {
            guard let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "HomeVC") as? TabController else {
                fatalError("Could not instantiate HomeVC!")
            }
            window.rootViewController = vc
        } else {
            guard let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "AuthVC") as? AuthViewController else {
                fatalError("Could not instantiate HomeVC!")
            }
            window.rootViewController = vc
        }

        self.window = window

        window.makeKeyAndVisible()
    }

}

AppDelegate.swift

//
//  AppDelegate.swift
//  Created by Don Mag on 3/27/20.
//

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window : UIWindow?
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]?) -> Bool {
            if #available(iOS 13, *) {
                // do only pure app launch stuff, not interface stuff
            } else {

                print("App Delegate didFinishLaunching... isLoggedIn:", UserDefaults.standard.bool(forKey: "isLoggedIn"))

                self.window = UIWindow()

                if UserDefaults.standard.bool(forKey: "isLoggedIn") {
                    guard let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "HomeVC") as? TabController else {
                        fatalError("Could not instantiate HomeVC!")
                    }
                    window?.rootViewController = vc
                } else {
                    guard let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "AuthVC") as? AuthViewController else {
                        fatalError("Could not instantiate HomeVC!")
                    }
                    window?.rootViewController = vc
                }

                window?.makeKeyAndVisible()

            }
            return true
    }

    // MARK: UISceneSession Lifecycle

    // iOS 13+ only
    @available(iOS 13.0, *)
    func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
        return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
    }
    // iOS 13+ only
    @available(iOS 13.0, *)
    func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {
    }

}

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