从一个 UINavigationController 到另一个 UINavigationController (Swift iOS 9, xcode 7)

Question

作为 iOS 开发的新手，我很好奇在我需要根据某些条件从初始 UINavigationController 分支到另一个 UINavigationController 的情况下，最好的方法是什么。例如，当用户第一次启动应用程序时，我想呈现“创建帐户”系列屏幕（我需要有多个屏幕）。但是，如果它们已经被激活，我希望能够分支到另一个 UINavigationController，它的根视图控制器是密码输入屏幕，后面还有更多屏幕。人们是怎么做这种事情的？我尝试将代码放在主导航控制器的 viewDidLoad() 方法中，然后在检查条件后调用 performSegueWithIdentifier（例如，密码是否存在），但是当我继续时，我得到一个空白屏幕，因为它显示的是另一个 UINavigationController 而不是根控制器它指向。我究竟做错了什么？我真的没有任何代码要显示，只是想举个例子，或者是否有首选的方法来做这种事情。

难道我不能做这样的事情吗？

Answer 1

在应用程序启动时，检查帐户是否已创建/登录，如果是，则创建 Home 导航控制器并将其设置为rootViewController。如果没有，请创建 CreateAccount 导航控制器并将其设置为rootViewController。

在帐户创建流程的最后，您可以在 CreateAccount 导航控制器的顶部显示 Home 导航控制器模态。这不是什么大问题，因为在下次启动时，您将只实例化 Home 导航控制器。

这就是我要说的：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // ...
    UIViewController *rootController = nil;
    BOOL showCreateAccount = NO; // this should come from some storage e.g. NSUserDefaults
    if(showCreateAccount == NO)
    {
        rootController = homeController; // create homeController 
    }
    else
    {
        rootController = createAccountController; // create createAccountController
    }

    NSAssert(rootController, @"no user interface, what is this? a web service??");
    self.window.rootViewController = rootController;
    [self.window makeKeyAndVisible];
    return YES;
}

如果您真的想从视图层次结构中删除 CreateAccount 控制器并将其替换为 Home 控制器，您应该创建一个自定义 segue。 This Stackoverflow Question 应该可以帮助您入门。

Answer 2

这就是我让它在 Swift 中工作的方式：

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    // Override point for customization after application launch.

    let activated = false || false
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let navController = activated ? "createAccount" : "enterPassword"

    let navViewController = storyboard.instantiateViewControllerWithIdentifier(navController) as! UINavigationController

    window?.rootViewController = navViewController
    window?.makeKeyAndVisible()

    return true
}

Answer 3

您可以在一个 VC 中完成所有这些工作。为例如创建手势识别器。向上滑动和向下滑动，然后为每个单独的设置使用开关盒。您可以轻松地为向上滑动添加计数器 +1，为向下滑动添加 -1，因此您甚至可以返回手势识别器。

然后您进行更改的方式是通过例如。在每种情况下为您的标签提供新文本

    switch swipeCounter {
      case 1: 
      label.text = "do this"
      funcForSomething()
      default:
      label.text = "do that"
      funcForSomethingElse()
   }

这是一个更完整的示例，您可能可以使用 (Swift 2)

请注意，我声明了 var upSwipes，然后用于检查我在序列中的位置。查看我的“案例 0”的屏幕截图。

    var upSwipes = 0

  override func viewDidLoad() {
    super.viewDidLoad()

    self.openingText.alpha = 0.0
    self.swipeUp.alpha = 0.0

    let swipeRight = UISwipeGestureRecognizer(target: self, action: "respondToSwipeGesture:")
    swipeRight.direction = UISwipeGestureRecognizerDirection.Right
    self.view.addGestureRecognizer(swipeRight)

    let swipeUp = UISwipeGestureRecognizer(target: self, action: "respondToSwipeGesture:")
    swipeUp.direction = UISwipeGestureRecognizerDirection.Up
    self.view.addGestureRecognizer(swipeUp)

    let swipeDown = UISwipeGestureRecognizer(target: self, action: "respondToSwipeGesture:")
    swipeDown.direction = UISwipeGestureRecognizerDirection.Down
    self.view.addGestureRecognizer(swipeDown)

  }


 func respondToSwipeGesture(gesture: UIGestureRecognizer) {

    if let swipeGesture = gesture as? UISwipeGestureRecognizer {


      switch swipeGesture.direction {
      case UISwipeGestureRecognizerDirection.Down:
        print("minus 1")
        if upSwipes != 0 { upSwipes = upSwipes - 1}
      case UISwipeGestureRecognizerDirection.Up:
        print("plus 1")
              upSwipes = upSwipes + 1
      default: print("other direction")
      }

        switch upSwipes {
        case 0:
          self.openingText.alpha = 0.0
          self.swipeUp.alpha = 0.0
          self.openingText.text = "Swipe up, not down you silly ?"
          self.openingText.alpha = 1.0
          self.swipeUp.alpha = 1.0
        case 1:
          self.openingText.alpha = 0.0
          self.swipeUp.alpha = 0.0
          self.openingText.text = "Case specific text. Please swipe up again."
          self.openingText.alpha = 1.0
          self.swipeUp.alpha = 1.0
          // Sequence to tell specifically why you need GPS permission and that in the next frame you will ask for it          
        case 2:
          self.openingText.alpha = 0.0
          self.swipeUp.alpha = 0.0
        //          initialAuthorization() // Your func to ask for GPS permission
          // Sequence to ask eg. GPS use permission
        case 3:
          self.openingText.alpha = 0.0
          self.swipeUp.alpha = 0.0
          self.openingText.text = "Case specific text. Please swipe up again."
          self.openingText.alpha = 1.0
          self.swipeUp.alpha = 1.0
          // Sequence to eg. ask name
        case 4:
          self.openingText.alpha = 0.0
          self.swipeUp.alpha = 0.0
          self.openingText.text = "Case specific text. Please swipe up again."
          self.openingText.alpha = 1.0
          self.swipeUp.alpha = 1.0
          // Sequence to eg. send verification email
        default:
          self.openingText.alpha = 0.0
          self.swipeUp.alpha = 0.0

            let vc = storyboard?.instantiateViewControllerWithIdentifier("initilizing-done") as! InitializingDoneViewController
            presentViewController(vc, animated: true, completion: nil)
          // Then finally you might choose to go to other view controller. You need file (Cocoa class) with the same name InitializingDoneViewController.swift and VC whose specification will then be used for this VC that is modally shown herein.
        }
    }