警告: 尝试显示 * on * ，其视图不在窗口层次结构中-迅速

我试图提出一个 ViewController 如果有任何保存的数据在数据模型。但我得到了以下错误:

警告: 试图显示 * on * 其视图不在窗口层次结构中”

相关守则:

override func viewDidLoad() {
super.viewDidLoad()
loginButton.backgroundColor = UIColor.orangeColor()


var request = NSFetchRequest(entityName: "UserData")
request.returnsObjectsAsFaults = false


var appDel:AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
var context:NSManagedObjectContext = appDel.managedObjectContext!


var results:NSArray = context.executeFetchRequest(request, error: nil)!


if(results.count <= 0){
print("Inga resultat")
} else {
print("SWITCH VIEW PLOX")
let internVC = self.storyboard?.instantiateViewControllerWithIdentifier("internVC") as internViewController
self.presentViewController(internVC, animated: true, completion: nil)
}
}

我已经尝试了不同的解决方案，发现使用谷歌没有成功。

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最佳答案

At this point in your code the view controller's view has only been created but not added to any view hierarchy. If you want to present from that view controller as soon as possible you should do it in viewDidAppear to be safest.

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In objective c: This solved my problem when presenting viewcontroller on top of mpmovieplayer

- (UIViewController*) topMostController
{
UIViewController *topController = [UIApplication sharedApplication].keyWindow.rootViewController;


while (topController.presentedViewController) {
topController = topController.presentedViewController;
}


return topController;
}
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for SWIFT

func topMostController() -> UIViewController {
var topController: UIViewController = UIApplication.sharedApplication().keyWindow!.rootViewController!
while (topController.presentedViewController != nil) {
topController = topController.presentedViewController!
}
return topController
}
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let storyboard = UIStoryboard(name: "test", bundle: nil)
let vc = storyboard.instantiateViewController(withIdentifier: "teststoryboard") as UIViewController
UIApplication.shared.keyWindow?.rootViewController?.present(vc, animated: true, completion: nil)

This seemed to work to make sure it's the top most view.

I was getting an error

Warning: Attempt to present myapp.testController: 0x7fdd01703990 on myapp.testController: 0x7fdd01703690 whose view is not in the window hierarchy!

Hope this helps others with swift 3

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Swift 3

I had this keep coming up as a newbie and found that present loads modal views that can be dismissed but switching to root controller is best if you don't need to show a modal.

I was using this

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc  = storyboard?.instantiateViewController(withIdentifier: "MainAppStoryboard") as! TabbarController
present(vc, animated: false, completion: nil)

Using this instead with my tabController:

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let view = storyboard.instantiateViewController(withIdentifier: "MainAppStoryboard") as UIViewController
let appDelegate = UIApplication.shared.delegate as! AppDelegate
//show window
appDelegate.window?.rootViewController = view

Just adjust to a view controller if you need to switch between multiple storyboard screens.

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You just need to perform a selector with a delay - (0 seconds works). 

override func viewDidLoad() {
super.viewDidLoad()
perform(#selector(presentExampleController), with: nil, afterDelay: 0)
}


@objc private func presentExampleController() {
let exampleStoryboard = UIStoryboard(named: "example", bundle: nil)
let exampleVC = storyboard.instantiateViewController(withIdentifier: "ExampleVC") as! ExampleVC
present(exampleVC, animated: true)
}
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For swift 3.0 and above

public static func getTopViewController() -> UIViewController?{
if var topController = UIApplication.shared.keyWindow?.rootViewController
{
while (topController.presentedViewController != nil)
{
topController = topController.presentedViewController!
}
return topController
}
return nil}
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Swift 3.

Call this function to get the topmost view controller, then have that view controller present.

func topMostController() -> UIViewController {
var topController: UIViewController = UIApplication.shared.keyWindow!.rootViewController!
while (topController.presentedViewController != nil) {
topController = topController.presentedViewController!
}
return topController
}

Usage:

let topVC = topMostController()
let vcToPresent = self.storyboard!.instantiateViewController(withIdentifier: "YourVCStoryboardID") as! YourViewController
topVC.present(vcToPresent, animated: true, completion: nil)
小开

I have tried so many approches! the only useful thing is:

if var topController = UIApplication.shared.keyWindow?.rootViewController
{
while (topController.presentedViewController != nil)
{
topController = topController.presentedViewController!
}
}
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Swift 4

func topMostController() -> UIViewController {
var topController: UIViewController = UIApplication.shared.keyWindow!.rootViewController!
while (topController.presentedViewController != nil) {
topController = topController.presentedViewController!
}
return topController
}
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All implementation for topViewController here are not fully supporting cases when you have UINavigationController or UITabBarController, for those two you need a bit different handling:

For UITabBarController and UINavigationController you need a different implementation.

Here is code I'm using to get topMostViewController:

protocol TopUIViewController {
func topUIViewController() -> UIViewController?
}


extension UIWindow : TopUIViewController {
func topUIViewController() -> UIViewController? {
if let rootViewController = self.rootViewController {
return self.recursiveTopUIViewController(from: rootViewController)
}


return nil
}


private func recursiveTopUIViewController(from: UIViewController?) -> UIViewController? {
if let topVC = from?.topUIViewController() { return recursiveTopUIViewController(from: topVC) ?? from }
return from
}
}


extension UIViewController : TopUIViewController {
@objc open func topUIViewController() -> UIViewController? {
return self.presentedViewController
}
}


extension UINavigationController {
override open func topUIViewController() -> UIViewController? {
return self.visibleViewController
}
}


extension UITabBarController {
override open func topUIViewController() -> UIViewController? {
return self.selectedViewController ?? presentedViewController
}
}
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Rather than finding top view controller, one can use

viewController.modalPresentationStyle = UIModalPresentationStyle.currentContext

Where viewController is the controller which you want to present This is useful when there are different kinds of views in hierarchy like TabBar, NavBar, though others seems to be correct but more sort of hackish

The other presentation style can be found on apple doc

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I was getting this error while was presenting controller after the user opens the deeplink. I know this isn't the best solution, but if you are in short time frame here is a quick fix - just wrap your code in asyncAfter:

DispatchQueue.main.asyncAfter(deadline: .now() + 0.7, execute: { [weak self] in
navigationController.present(signInCoordinator.baseController, animated: animated, completion: completion)
})

It will give time for your presenting controller to call viewDidAppear.

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The previous answers relate to the situation where the view controller that should present a view 1) has not been added yet to the view hierarchy, or 2) is not the top view controller.
Another possibility is that an alert should be presented while another alert is already presented, and not yet dismissed.

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Swift Method, and supply a demo.

func topMostController() -> UIViewController {
var topController: UIViewController = UIApplication.sharedApplication().keyWindow!.rootViewController!
while (topController.presentedViewController != nil) {
topController = topController.presentedViewController!
}
return topController
}


func demo() {
let vc = ViewController()
let nav = UINavigationController.init(rootViewController: vc)
topMostController().present(nav, animated: true, completion: nil)
}
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Swift 5.1:

let storyboard = UIStoryboard.init(name: "Main", bundle: Bundle.main)
let mainViewController = storyboard.instantiateViewController(withIdentifier: "ID")
let appDeleg = UIApplication.shared.delegate as! AppDelegate
let root = appDeleg.window?.rootViewController as! UINavigationController
root.pushViewController(mainViewController, animated: true)
小开

Use of main thread to present and dismiss view controller worked for me.

DispatchQueue.main.async { self.present(viewController, animated: true, completion: nil) }

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