更改ViewController并重新启动应用程序。

Question

我做了两个ViewController，如何将根ViewController从ViewController()改为MainView()？下面是我在SceneDelegate中的代码

guard let windowScene = (scene as? UIWindowScene) else { return }
window = UIWindow(windowScene: windowScene)
window?.makeKeyAndVisible()
window?.backgroundColor = UIColor.black
if isNewUser == true {
     window?.rootViewController = ViewController()
} else {
     window?.rootViewController = MainView()
}

当我运行应用程序时，测试isNewUser = true和isNewUser = false时，这个工作正常。

在我的ViewController中

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        //Show the welcome screen, blah.
        //Accept the location, blah.
        //After accepted everything, change isNewUser to false in UserDefault.Standard
        print("App is restart")
    }
}

class MainView: UITabBarController, UITabBarControllerDelegate {
    override func viewDidLoad() {
        super.viewDidLoad()
        print("Welcome to AiOO!")
    }
}

两者都能正常工作，但比如说，当我完成接受协议或接受位置时，第一次运行应用程序时......会在UserDefault.standard中将isNewUser设置为false。所以只有一件事我被卡住了，我怎么才能重启应用或者将rootViewController切换到MainView()？

UPDATED:RestartApp，当我点击 "Complete "按钮时，没有UITabBarControl，也不会调用MainView，直到我杀死应用程序并再次打开，它才会工作:( 以下是我的完整代码。

在SceneDelegate:

var versioncheck = "1.0.0.0"

class SceneDelegate: UIResponder, UIWindowSceneDelegate, RestartApp {

    var window: UIWindow?

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        sceneRestore()
        guard let windowScene = (scene as? UIWindowScene) else { return }
        window = UIWindow(windowScene: windowScene)
        window?.makeKeyAndVisible()
        window?.backgroundColor = UIColor(named: "Main Background")
        restartApp()
    }
    func restartApp() {
        if !UserDefaults.standard.bool(forKey: "New User") {UserDefaults.standard.set(true, forKey: "New User")}
        let isNewUser = UserDefaults.standard.bool(forKey: "New User")
        print(isNewUser) // It will keep say "true" even change to false in UserDefault
        if isNewUser == true {
            window?.rootViewController = ViewController()
        } else if versioncheck != "1.0.0.0" {
            window?.rootViewController = NewUpdate()
        } else {
            window?.rootViewController = MainView()
        }
    }
}

ViewController

protocol RestartApp {
    func restartApp()
}
class ViewController: UIViewController {
    var delegate: RestartApp?
    override func viewDidLoad() {
        super.viewDidLoad()
        welcomePage()
    }
}

当我点击 "完成 "按钮时，它会调用。

@objc func welcomeChangeGoToMain () {
    UserDefaults.standard.set(false, forKey: "New User")
    print(UserDefaults.standard.bool(forKey: "New User")) //It said "false"
    welcomeTitle.removeFromSuperview()
    welcomeSubline.removeFromSuperview()
    welcomeNext.removeFromSuperview()
    welcomeRequest.removeFromSuperview()
    self.delegate?.restartApp()
}

Answer 1

你可以创建一个委托协议，每当isNewUser值被改变时被调用，并在场景类内调用它的委托函数，以呈现基于该值的视图控制器。像下面这样。

在你的SceneDelegate类里面。

 // don't forget to assign the RestartApp Delegate here
class SceneDelegate: UIResponder, UIWindowSceneDelegate, RestartApp {

    var window: UIWindow?

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    guard let windowScene = (scene as? UIWindowScene) else { return }
    window = UIWindow(windowScene: windowScene)
    window?.makeKeyAndVisible()
    restartApp()
}

并在sceneDelegate中创建restartApp函数。

    func restartApp() {
        let isNewUser = UserDefaults.standard.bool(forKey: "Key")
        if isNewUser == true {
           window?.rootViewController = ViewController()
        } else {
           window?.rootViewController = ViewController2()
        }
}

在你想要重启函数被调用的最后，创建协议和它的委托调用，如下面。

protocol RestartApp {
  func restartApp()
}

class ViewController2: UIViewController {

var delegate: RestartApp?

override func viewDidLoad() {
    super.viewDidLoad()
    UserDefaults.standard.set(true, forKey: "Key")
    view.backgroundColor = .yellow
    print("VC2")
    self.delegate?.restartApp() // this should be called wherever you want to restart the app ( inside an action or a function depends on your need )
}

}

总而言之，这里发生了什么，应用程序启动时，它在SceneDelegate类中调用willConnectTo函数，这个函数调用重启应用程序，并根据保存在IsNewUser中的最后一个值调用VC，然后在你的VC中，每次你调用self.delegate.restartApp()，它在SceneDelegate中调用重启函数，并根据你的isNewUser值调用VC。