导航栏消失更改根视图控制器，然后重新分配

Question

我的启动屏幕是根视图，而我的应用向firebase发出请求，然后在请求完成后重新分配根视图。不幸的是，当我这样做时，我的导航栏消失或被新的根视图覆盖。当我运行模拟器时，我可以简要地看到导航栏，然后它被我的TableViewController覆盖。我如何避免这种情况发生？

下面是从AppDelegate中我的代码，我做这一切的发生：

var window: UIWindow? 
let searchManager = SearchManager() 

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool { 
    makeRootViewLaunchScreen() 
    FirebaseApp.configure() 
    searchManager.getMosaicTitles { results in 
     self.searchManager.listOfMosaics = results 
     self.stopDisplayingLaunchScreen() 
    } 
    // Adds border to bottom of the nav bar 
    UINavigationBar.appearance().shadowImage = UIImage.imageWithColor(color: UIColor(red:0.00, green:0.87, blue:0.39, alpha:1.0)) 
    // Override point for customization after application launch. 
    return true 
} 

func makeRootViewLaunchScreen() { 
    let mainStoryboard: UIStoryboard = UIStoryboard(name: "LaunchScreen", bundle: nil) 
    let viewController = mainStoryboard.instantiateViewController(withIdentifier: "launchScreen") 
    UIApplication.shared.keyWindow?.rootViewController = viewController 
} 

func stopDisplayingLaunchScreen() { 
    let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil) 
    let viewController = mainStoryboard.instantiateViewController(withIdentifier: "centralViewController") as? SearchResultsTableViewController 
    viewController?.searchManager = searchManager 
    UIApplication.shared.keyWindow?.rootViewController = viewController 
    UIApplication.shared.keyWindow?.rootViewController?.navigationController?.isNavigationBarHidden = false 
} 

正如你可以看到我试图用UIApplication.shared.keyWindow?.rootViewController?.navigationController?.isNavigationBarHidden = false迫使导航栏出现，但事实并非如此。我的应用看起来仍然是这样的：

Answer 1

您正在设置一个UIViewController作为您的根控制器。你想要做的是设置一个UINavigationController作为你的根控制器。

既可以在你的故事板新的导航控制器和负载的那一个，而不是装载“centralViewController”，或修改您的函数是这样的：

func stopDisplayingLaunchScreen() { 
    let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil) 

    if let viewController = mainStoryboard.instantiateViewController(withIdentifier: "centralViewController") as? SearchResultsTableViewController { 

     viewController.searchManager = searchManager 

     // create a new UINavigationController 
     let newNavVC = UINavigationController() 

     // set the "root" VC of the NavVC to your SearchResultsTableViewController 
     newNavVC.setViewControllers([viewController], animated: false) 

     // use the new NavVC as the new rootViewController 
     UIApplication.shared.keyWindow?.rootViewController = newNavVC 
     UIApplication.shared.keyWindow?.rootViewController?.navigationController?.isNavigationBarHidden = false 

    } 
} 

注：没有测试，但是这应该让你对你的办法。

编辑：另一种方法...

而不是交换的关键窗口的根控制器，创建一个视图控制器，指示要初始化/检索数据。该VC可以是导航控制器的“根”。

把你的searchManager.getMosaicTitles函数写入即 VC。当它完成时，用您的TableVC替换您的导航控制器中的当前“启动”控制器。它看起来像这样：

// note: searchManager will have to be a reference back to AppDelegate.searchManager 
searchManager.getMosaicTitles { results in 
    self.searchManager.listOfMosaics = results 

    let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil) 

    if let viewController = mainStoryboard.instantiateViewController(withIdentifier: "centralViewController") as? SearchResultsTableViewController { 

     viewController.searchManager = searchManager 

     // replace the current Nav VC stack with the new SearchResultsTableViewController 
     self.navigationController.setViewControllers([viewController], animated: false) 

    } 
} 

Answer 2

为了防止导航栏控制器出现和出现tableView之间的延迟，请查看以下内容。 Prevent navigation bar from disappearing without lag