無法在迅速

Question

作爲在新迅速從故事板作爲RootViewController的實例化的viewController，我試圖用故事板使用去的LoginController下面的代碼

var window: UIWindow? 

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool 
{ 

    var type = UIUserNotificationType.Badge | UIUserNotificationType.Alert | UIUserNotificationType.Sound; 
    var setting = UIUserNotificationSettings(forTypes: type, categories: nil); 
    UIApplication.sharedApplication().registerUserNotificationSettings(setting); 
    UIApplication.sharedApplication().registerForRemoteNotifications(); 

    var navCtrl = UINavigationController(); 
    var isLoggedIn = NSUserDefaults.standardUserDefaults().boolForKey(USERDEFAULT_ISLOGGEDIN); 
    if(isLoggedIn) 
    { 
     let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil) 
     var mainController: CategoriesController = mainStoryboard.instantiateViewControllerWithIdentifier(SEGUE_CATEGORIES) as CategoriesController 
     navCtrl.pushViewController(mainController, animated: true); 
    } 
    else 
    { 
     let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil) 
     var mainController: LoginController = mainStoryboard.instantiateViewControllerWithIdentifier(SEGUE_LOGIN) as LoginController 
     navCtrl.pushViewController(mainController, animated: true); 
    } 

    self.window?.rootViewController = navCtrl; 
    self.window?.makeKeyAndVisible(); 

    return true 
} 

但是它只是顯示空白屏幕。將navController分配爲rootViewController有什麼不妥？

Answer 1

您還沒有創建窗口，所以self.window將爲零。僅當您從xib或故事板啓動應用程序時，系統纔會創建窗口。如果你不使用這些，你必須自己創建它。

由於您通過使用?有條件地解包，navCtrl的賦值和對makeKeyAndVisible（）的調用根本不會被執行。

使用前只需創建一個UIWindow：

func application(application: UIApplication!, didFinishLaunchingWithOptions launchOptions: NSDictionary!) -> Bool { 
    self.window = UIWindow(frame: UIScreen.mainScreen().bounds) 
    // ... 
    self.window!.rootViewController = navCtrl; 
    self.window!.makeKeyAndVisible(); 
    return true 
} 

我會推薦給解開涉及window與!所有呼叫。沒有窗口應該是一個錯誤。

Answer 2

試試這種方法。我想你不能推UINavigationController，直到你設置它的根ViewController。

var navCtrl 
let isLoggedIn = NSUserDefaults.standardUserDefaults().boolForKey(USERDEFAULT_ISLOGGEDIN); 
if (isLoggedIn) 
{ 
    let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil) 
    var mainController: CategoriesController = mainStoryboard.instantiateViewControllerWithIdentifier(SEGUE_CATEGORIES) as CategoriesController 

    navCtrl = UINavigationController(rootViewController:mainController) 
} 
else 
{ 
    let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil) 
    var mainController: LoginController = mainStoryboard.instantiateViewControllerWithIdentifier(SEGUE_LOGIN) as LoginController 
    navCtrl = UINavigationController(rootViewController:mainController) 
}