以编程方式创建带有后退按钮的导航控制器

Question

我无法在我的 AppDelegate 中快速解决问题。数周来，我一直在研究这个小问题（在后台，而不是连续），并进行了大量的谷歌搜索。我一定是错过了什么。

当远程通知进入我的 iOS 应用程序时，我想以模态方式呈现适合消息的视图，并带有一个带有后退按钮的 UINavigationController。这个想法是，当用户处理完通知后，他们可以按“返回”并返回到原来的位置。我无法以编程方式在导航控制器中显示“返回”按钮。

并非所有我现有的视图都嵌入在导航控制器中。因此，我没有在堆栈中找到现有的 UINavigationController，而是创建了一个新的 UINavigationController 并尝试将其设置并呈现如下：

    let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
    var mvc = mainStoryboard.instantiateViewControllerWithIdentifier("MyViewIdentifier") as! MySpecialViewController

    /* here is where I setup the necessary variables in the mvc view controller, using data from the remote message.  You don't need to see all that */

    /* this seems to work, I do get what looks to be a navigation controller */
    let newNavController = UINavigationController(rootViewController: mvc)

    /* this part doesn't work, I don't get a "Back" button */
    let btn = UIBarButtonItem(title: "back", style: UIBarButtonItemStyle.Done, target: mvc, action: "backPressed")
    newNavController.navigationItem.leftBarButtonItem = btn

    /* this block seems to work.  The idea is to work through the hierarchy of any modal presentations
    until we get to the screen that is actually showing right now.  I'm not    
    sure this will work in all situations, but it seems to work in my app's hierarchy. */
    var currentViewController = self.window!.rootViewController
    while currentViewController?.presentedViewController != nil {
        currentViewController = currentViewController?.presentedViewController
    }

    /* this I suppose shows my new view controller modally, except without
    the "back" button it's hard to be sure the navigation controller is even there. */
    currentViewController?.presentViewController(newNavController, animated: true, completion: nil)

我在相关视图控制器中确实有一个名为“backPressed”的方法。

关于为什么导航栏按钮没有显示的任何线索？

编辑：我知道 backBarButtonItem 只有在我们不在堆栈顶部时才会显示。但是，即使我们在堆栈的顶部，leftBarButtonItem 也应该出现？

Answer 1

这是一个简单的例子，可以从第一个视图以编程方式设置导航栏：

if let resultController = storyboard!.instantiateViewControllerWithIdentifier("SecondView") as? SecondView {
    let navController = UINavigationController(rootViewController: resultController) // Creating a navigation controller with resultController at the root of the navigation stack.
    self.presentViewController(navController, animated:true, completion: nil)
}

如果您想在导航中添加返回按钮，请将此代码用于SecondView.swift 类：

override func viewDidLoad() {
super.viewDidLoad()

   let backButton = UIBarButtonItem(title: "Back", style: UIBarButtonItemStyle.Plain, target: self, action: "goBack")
   navigationItem.leftBarButtonItem = backButton

}

func goBack(){
    dismissViewControllerAnimated(true, completion: nil)
}

如果您想从 firstView 执行所有这些操作，那么这里是您的代码：

@IBAction func btnPressed(sender: AnyObject) {


if let resultController = storyboard!.instantiateViewControllerWithIdentifier("SecondView") as? SecondView {
    resultController.navigationItem.leftBarButtonItem = UIBarButtonItem(title: "Back", style: UIBarButtonItemStyle.Plain, target: self, action: "goBack")
    let navController = UINavigationController(rootViewController: resultController) // Creating a navigation controller with VC1 at the root of the navigation stack.
    self.presentViewController(navController, animated:true, completion: nil)
    }
}

func goBack(){
    dismissViewControllerAnimated(true, completion: nil)
}

希望这会对你有所帮助。

Answer 2

我认为您的视图控制器被不止一个 segue 使用？

在故事板中，您可以将视图控制器嵌入到导航控制器中。

对于模态显示，您选择导航控制器而不是视图控制器。这将为模态演示提供一个栏。

完成按钮更有可能用于关闭模式演示。 （用户可能会对后退按钮的非典型用法感到困惑，因为您呈现的导航控制器并未将视图控制器从其堆栈中弹出。）