UINavigationController不会pushViewController

Question

我有两个ViewControllers。一个叫做LoginVC，也是我的根视图控制器，另一个叫做SignUpVC。

在我的AppDelegate中，我这样设置了我的UINavigationbar：

var window: UIWindow?

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

    window = UIWindow()
    window?.rootViewController = UINavigationController(rootViewController: LoginVC())

    return true
}

然后在我的LoginVC中，我使用此命令来显示我的SignUpVC，但它不起作用。

@objc func handleShowSignUp() {
    let signUpVC = SignUpVC()
    navigationController?.pushViewController(signUpVC, animated: true)
}

有人能给我解释一下我哪里做错了吗？

Answer 1

您应该以这种方式使用文件SceneDelegate：

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow? // create Window

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        let LoginVC = ViewController() //create your viewController
        nav.pushViewController(contentView, animated: true) 
               if let windowScene = scene as? UIWindowScene {
                   let window = UIWindow(windowScene: windowScene)
                   window.rootViewController = LoginVC
                   SceneDelegate.window = window
                   window.makeKeyAndVisible()
               }
    }

重要提示:您可以检查UIWindowScene

Answer 2

直接初始化LoginVC()和SignUpVC()是错误的。如果您使用的是故事板，请尝试以下内容

let storyboard = UIStoryboard.init(name: "YOUR_STORYBOARD_NAME", bundle: nil)
let nav = storyboard.instantiateInitialViewController() //if you want the initial one

let storyBoard: UIStoryboard = UIStoryboard(name: "YOUR_STORYBOARD_NAME", bundle: nil)
let someVC: SomeViewController = giftStoryBoard.instantiateViewController(withIdentifier: "SomeViewController") as! SomeViewController //don't forget to set identifier on interfacebuilder

如果您只使用.xib

let myViewController = MyViewController(nibName: "MyViewController", bundle: nil)

然后尝试将其推送到导航控制器

Answer 3

这在SceneDelegate-file中起到了作用：

    @available(iOS 13.0, *)
func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {

    guard let scene = scene as? UIWindowScene else { return }
    window = UIWindow(windowScene: scene)
    window?.rootViewController = UINavigationController(rootViewController: LoginVC())
    window?.makeKeyAndVisible()
}