ios - Navigation Bar 消失 Change Root ViewController 然后重新赋值

Question

我已将启动屏幕设置为 Root View ，同时我的应用程序向 firebase 发出请求，然后在请求完成后重新分配 Root View 。不幸的是，当我这样做时，我的导航栏消失或被新的 Root View 覆盖。当我运行模拟器时，我可以短暂地看到导航栏，然后它被我的 TableViewController 覆盖了。我该如何防止这种情况发生？

这是我在 AppDelegate 中实现这一切的代码:

    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
}

如您所见，我尝试使用 UIApplication.shared.keyWindow?.rootViewController?.navigationController?.isNavigationBarHidden = false 强制显示导航栏，但它没有出现。我的应用程序仍然如下所示:

Answer 1

您正在将 UIViewController 设置为您的 Root Controller 。您要做的是将 UINavigationController 设置为您的 Root Controller 。

要么在你的 Storyboard中创建一个新的导航 Controller 并加载它而不是加载“centralViewController”，要么像这样修改你的函数:

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

    }
}

注意:未经测试，但这应该可以帮助您上路。

编辑:另一种方法......

不是交换键窗口的根 Controller ，而是创建一个 ViewController 来指示您正在初始化/检索数据。该 VC 可以是导航 Controller 的“根”。

将您的searchManager.getMosaicTitles 函数放在那个 VC 中。完成后，将 Nav Controller 中的当前“启动” Controller 替换为 TableVC。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)

    }
}