如何获得根视图控制器？

我需要一个根视图控制器实例。

我尝试了这些方法：

UIViewController *rootViewController = (UIViewController*)[[[UIApplication sharedApplication] keyWindow] rootViewController];

返回： null：

另外，当我尝试获取控制器数组时：

NSArray *viewControllers = self.navigationController.viewControllers;

它仅返回一个控制器，但不是我的根视图控制器。

如果我尝试从导航控制器中获取：

UIViewController *root = (UIViewController*)[self.navigationController.viewControllers objectAtIndex:0];

返回： null：

有什么想法吗？我还能尝试获得根视图控制器的一个实例吗？

谢谢。

如果您尝试访问rootViewController在appDelegate中设置的。试试这个：

目标C

YourViewController *rootController = (YourViewController*)[[(YourAppDelegate*)
                                   [[UIApplication sharedApplication]delegate] window] rootViewController];

迅速

let appDelegate  = UIApplication.sharedApplication().delegate as AppDelegate
let viewController = appDelegate.window!.rootViewController as YourViewController

迅捷3

let appDelegate  = UIApplication.shared.delegate as! AppDelegate
let viewController = appDelegate.window!.rootViewController as! YourViewController

迅捷4和4.2

let viewController = UIApplication.shared.keyWindow!.rootViewController as! YourViewController

雨燕5＆5.1＆5.2

let viewController = UIApplication.shared.windows.first!.rootViewController as! YourViewController

目标C

UIViewController *controller = [UIApplication sharedApplication].keyWindow.rootViewController;

雨燕2.0

let viewController = UIApplication.sharedApplication().keyWindow?.rootViewController

迅捷5

let viewController = UIApplication.shared.keyWindow?.rootViewController

正如@ 0x7fffffff 在这里建议的那样，如果您有UINavigationController，则可以更轻松地完成操作：

YourViewController *rootController =
    (YourViewController *)
        [self.navigationController.viewControllers objectAtIndex: 0];

上面答案中的代码返回UINavigation控制器（如果有），并且如果需要，可以使用self.navigationController。

除非您有充分的理由，否则请在根控制器中执行以下操作：

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(onTheEvent:)
                                             name:@"ABCMyEvent"
                                           object:nil];

当您想通知它时：

[[NSNotificationCenter defaultCenter] postNotificationName:@"ABCMyEvent"
                                                object:self];                

迅捷3

let rootViewController = UIApplication.shared.keyWindow?.rootViewController

快速的方法，您可以在任何地方调用它，它返回可选的，因此请注意：

/// EZSwiftExtensions - Gives you the VC on top so you can easily push your popups
var topMostVC: UIViewController? {
    var presentedVC = UIApplication.sharedApplication().keyWindow?.rootViewController
    while let pVC = presentedVC?.presentedViewController {
        presentedVC = pVC
    }

    if presentedVC == nil {
        print("EZSwiftExtensions Error: You don't have any views set. You may be calling them in viewDidLoad. Try viewDidAppear instead.")
    }
    return presentedVC
}

它作为标准功能包括在：

https://github.com/goktugyil/EZSwiftExtensions

Swift 3：在没有Segue的情况下 使用Chage ViewController并发送AnyObject使用：目标ViewController上的Identity MainPageViewController

let mainPage = self.storyboard?.instantiateViewController(withIdentifier: "MainPageViewController") as! MainPageViewController

var mainPageNav = UINavigationController(rootViewController: mainPage)

self.present(mainPageNav, animated: true, completion: nil)

或者如果您想更改View Controller并发送数据

let mainPage = self.storyboard?.instantiateViewController(withIdentifier: "MainPageViewController") as! MainPageViewController

let dataToSend = "**Any String**" or  var ObjectToSend:**AnyObject** 

mainPage.getData = dataToSend 

var mainPageNav = UINavigationController(rootViewController: mainPage)

self.present(mainPageNav, animated: true, completion: nil)