ios - 其 View 不在窗口层次结构中的LoginViewController!在Appldelegate中

我的目标是检查密钥链中是否有令牌，如果没有，则只显示登录视图控制器屏幕。现在的问题是，我得到了这个错误。我在AppDelegate.swift中编写了这段代码
.LoginViewController:0x7ff59b619820>其视图不在窗口层次结构中！
这是密码

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

     let keychain = Keychain(server: "https://app.herokuapp.com", protocolType: .HTTPS)

     if ((try? keychain.contains("token")) != nil) {
        showLoginScreen()
     } else {

     }
      return true
     }

    func showLoginScreen() -> Void {
        let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
        let setViewController = mainStoryboard.instantiateViewControllerWithIdentifier("loginView") as! LoginViewController
        let rootViewController = self.window!.rootViewController
        rootViewController?.presentViewController(setViewController, animated: false, completion: nil)
    }

最佳答案

试试这个
在出现前加上

self.window.makeKeyAndVisible()

更新

   let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
    let setViewController = mainStoryboard.instantiateViewControllerWithIdentifier("loginView") as! LoginViewController
      self.window.makeKeyAndVisible()
    self.window!.rootViewController.presentViewController(setViewController, animated: false, completion: nil)

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