blocks|key|2722771|text|presentViewController显示了一个视图控制器。它不返回视图控制器。如果您没有使用UINavigationController，那么您可能正在寻找presentedViewController，并且需要从根开始并向下迭代所显示的视图。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2722772|if+var+topController+=+UIApplication.sharedApplication().keyWindow?.rootViewController+{
++++while+let+presentedViewController+=+topController.presentedViewController+{
++++++++topController+=+presentedViewController
++++}

++++//+topController+should+now+be+your+topmost+view+controller
}|code-block|syntax|javascript|2722773|对于Swift+3%2B：|2722774|if+var+topController+=+UIApplication.shared.keyWindow?.rootViewController+{
++++while+let+presentedViewController+=+topController.presentedViewController+{
++++++++topController+=+presentedViewController
++++}

++++//+topController+should+now+be+your+topmost+view+controller
}|2722775|对于iOS+13%2B|2722776|let+keyWindow+=+UIApplication.shared.windows.filter+{$0.isKeyWindow}.first

if+var+topController+=+keyWindow?.rootViewController+{
++++while+let+presentedViewController+=+topController.presentedViewController+{
++++++++topController+=+presentedViewController
++++}

//+topController+should+now+be+your+topmost+view+controller
}|2722777|entityMap^0|0|L|1D|M|29|N|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|14|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|T|$]]

<code>presentViewController</code> shows a view controller. It doesn't return a view controller. If you're not using a <code>UINavigationController</code>, you're probably looking for <code>presentedViewController</code> and you'll need to start at the root and iterate down through the presented views.

<pre><code>if var topController = UIApplication.sharedApplication().keyWindow?.rootViewController {
 while let presentedViewController = topController.presentedViewController {
 topController = presentedViewController
 }

 // topController should now be your topmost view controller
}
</code></pre>

For Swift 3+:

<pre><code>if var topController = UIApplication.shared.keyWindow?.rootViewController {
 while let presentedViewController = topController.presentedViewController {
 topController = presentedViewController
 }

 // topController should now be your topmost view controller
}
</code></pre>

For iOS 13+

<pre><code>let keyWindow = UIApplication.shared.windows.filter {$0.isKeyWindow}.first

if var topController = keyWindow?.rootViewController {
 while let presentedViewController = topController.presentedViewController {
 topController = presentedViewController
 }

// topController should now be your topmost view controller
}
</code></pre>

blocks|key|146202|text|你把代码放在哪里了？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|146203|我在我的演示中尝试了你的代码，我发现，如果你把代码放在|146204|func+application(application:+UIApplication,+didFinishLaunchingWithOptions+launchOptions:+[NSObject:+AnyObject]?)+->+Bool+{+|code-block|syntax|javascript|146205|将失败，因为密钥窗口已经设置好了。|146206|146207|override+func+viewDidLoad()+{|146208|它就是这样的。|146209|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|T|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|U|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|V|8|@]|9|@]|A|$]]|$1|L|3|M|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|N|3|O|5|6|7|X|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|Q|$]]

Where did you put the code in?

I try your code in my demo, I found out, if you put the code in 

<pre><code>func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -&gt; Bool { 
</code></pre>

will fail, because key window have been setting yet. 

But I put your code in some view controller's 

<pre><code>override func viewDidLoad() {
</code></pre>

It just works.

blocks|key|145213|text|extension+UIWindow+{

++++func+visibleViewController()+->+UIViewController?+{
++++++++if+let+rootViewController:+UIViewController+=+self.rootViewController+{
++++++++++++return+UIWindow.getVisibleViewControllerFrom(vc:+rootViewController)
++++++++}
++++++++return+nil
++++}

++++static+func+getVisibleViewControllerFrom(vc:UIViewController)+->+UIViewController+{
++++++++if+let+navigationController+=+vc+as?+UINavigationController,
++++++++++++let+visibleController+=+navigationController.visibleViewController++{
++++++++++++return+UIWindow.getVisibleViewControllerFrom(+vc:+visibleController+)
++++++++}+else+if+let+tabBarController+=+vc+as?+UITabBarController,
++++++++++++let+selectedTabController+=+tabBarController.selectedViewController+{
++++++++++++return+UIWindow.getVisibleViewControllerFrom(vc:+selectedTabController+)
++++++++}+else+{
++++++++++++if+let+presentedViewController+=+vc.presentedViewController+{
++++++++++++++++return+UIWindow.getVisibleViewControllerFrom(vc:+presentedViewController)
++++++++++++}+else+{
++++++++++++++++return+vc
++++++++++++}
++++++++}
++++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|145214|用法：|unstyled|145215|if+let+topController+=+window.visibleViewController()+{
++++println(topController)
}|145216|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|L|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|I|3|-4|5|F|7|N|8|@]|9|@]|A|$]]]|J|$]]

<pre><code>extension UIWindow {

 func visibleViewController() -&gt; UIViewController? {
 if let rootViewController: UIViewController = self.rootViewController {
 return UIWindow.getVisibleViewControllerFrom(vc: rootViewController)
 }
 return nil
 }

 static func getVisibleViewControllerFrom(vc:UIViewController) -&gt; UIViewController {
 if let navigationController = vc as? UINavigationController,
 let visibleController = navigationController.visibleViewController {
 return UIWindow.getVisibleViewControllerFrom( vc: visibleController )
 } else if let tabBarController = vc as? UITabBarController,
 let selectedTabController = tabBarController.selectedViewController {
 return UIWindow.getVisibleViewControllerFrom(vc: selectedTabController )
 } else {
 if let presentedViewController = vc.presentedViewController {
 return UIWindow.getVisibleViewControllerFrom(vc: presentedViewController)
 } else {
 return vc
 }
 }
 }
}
</code></pre>

Usage:

<pre><code>if let topController = window.visibleViewController() {
 println(topController)
}
</code></pre>

blocks|key|143852|text|具有此扩展名|type|unstyled|depth|inlineStyleRanges|entityRanges|data|143853|Swift+2.*|offset|length|style|BOLD|143854|extension+UIApplication+{
++++class+func+topViewController(controller:+UIViewController?+=+UIApplication.sharedApplication().keyWindow?.rootViewController)+->+UIViewController?+{
++++++++if+let+navigationController+=+controller+as?+UINavigationController+{
++++++++++++return+topViewController(navigationController.visibleViewController)
++++++++}
++++++++if+let+tabController+=+controller+as?+UITabBarController+{
++++++++++++if+let+selected+=+tabController.selectedViewController+{
++++++++++++++++return+topViewController(selected)
++++++++++++}
++++++++}
++++++++if+let+presented+=+controller?.presentedViewController+{
++++++++++++return+topViewController(presented)
++++++++}
++++++++return+controller
++++}
}|code-block|syntax|javascript|143855|Swift+3|143856|extension+UIApplication+{
++++class+func+topViewController(controller:+UIViewController?+=+UIApplication.shared.keyWindow?.rootViewController)+->+UIViewController?+{
++++++++if+let+navigationController+=+controller+as?+UINavigationController+{
++++++++++++return+topViewController(controller:+navigationController.visibleViewController)
++++++++}
++++++++if+let+tabController+=+controller+as?+UITabBarController+{
++++++++++++if+let+selected+=+tabController.selectedViewController+{
++++++++++++++++return+topViewController(controller:+selected)
++++++++++++}
++++++++}
++++++++if+let+presented+=+controller?.presentedViewController+{
++++++++++++return+topViewController(controller:+presented)
++++++++}
++++++++return+controller
++++}
}|143857|你可以在你的控制器上的任何地方使用它|143858|if+let+topController+=+UIApplication.topViewController()+{

}|143859|entityMap^0|0|0|9|0|0|0|7|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@$D|Y|E|Z|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|10|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|11|8|@$D|12|E|13|F|G]]|9|@]|A|$]]|$1|O|3|P|5|J|7|14|8|@]|9|@]|A|$K|L]]|$1|Q|3|R|5|6|7|15|8|@]|9|@]|A|$]]|$1|S|3|T|5|J|7|16|8|@]|9|@]|A|$K|L]]|$1|U|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|V|$]]

have this extension

Swift 2.*

<pre><code>extension UIApplication {
 class func topViewController(controller: UIViewController? = UIApplication.sharedApplication().keyWindow?.rootViewController) -&gt; UIViewController? {
 if let navigationController = controller as? UINavigationController {
 return topViewController(navigationController.visibleViewController)
 }
 if let tabController = controller as? UITabBarController {
 if let selected = tabController.selectedViewController {
 return topViewController(selected)
 }
 }
 if let presented = controller?.presentedViewController {
 return topViewController(presented)
 }
 return controller
 }
}
</code></pre>

Swift 3

<pre><code>extension UIApplication {
 class func topViewController(controller: UIViewController? = UIApplication.shared.keyWindow?.rootViewController) -&gt; UIViewController? {
 if let navigationController = controller as? UINavigationController {
 return topViewController(controller: navigationController.visibleViewController)
 }
 if let tabController = controller as? UITabBarController {
 if let selected = tabController.selectedViewController {
 return topViewController(controller: selected)
 }
 }
 if let presented = controller?.presentedViewController {
 return topViewController(controller: presented)
 }
 return controller
 }
}
</code></pre>

You can you use this anywhere on your controller

<pre><code>if let topController = UIApplication.topViewController() {

}
</code></pre>

blocks|key|143861|text|基于Dianz答案，Objective-C版本|type|unstyled|depth|inlineStyleRanges|entityRanges|data|143862|-+(UIViewController+*)+topViewController+{
+++UIViewController+*baseVC+=+UIApplication.sharedApplication.keyWindow.rootViewController;
+++if+([baseVC+isKindOfClass:[UINavigationController+class]])+{
+++++++return+((UINavigationController+*)baseVC).visibleViewController;
+++}

+++if+([baseVC+isKindOfClass:[UITabBarController+class]])+{
+++++++UIViewController+*selectedTVC+=+((UITabBarController*)baseVC).selectedViewController;
+++++++if+(selectedTVC)+{
+++++++++++return+selectedTVC;
+++++++}
+++}

+++if+(baseVC.presentedViewController)+{
+++++++return+baseVC.presentedViewController;
+++}
+++return+baseVC;
}|code-block|syntax|javascript|143863|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Based on Dianz answer, the Objective-C version

<pre><code>- (UIViewController *) topViewController {
 UIViewController *baseVC = UIApplication.sharedApplication.keyWindow.rootViewController;
 if ([baseVC isKindOfClass:[UINavigationController class]]) {
 return ((UINavigationController *)baseVC).visibleViewController;
 }

 if ([baseVC isKindOfClass:[UITabBarController class]]) {
 UIViewController *selectedTVC = ((UITabBarController*)baseVC).selectedViewController;
 if (selectedTVC) {
 return selectedTVC;
 }
 }

 if (baseVC.presentedViewController) {
 return baseVC.presentedViewController;
 }
 return baseVC;
}
</code></pre>

blocks|key|2722923|text|我很喜欢@dianz's+answer，下面是swift+3的版本。它基本上是一样的，但是他的代码少了一个大括号，而且一些语法/变量/方法名也发生了变化。所以就是这样了！|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2722924|extension+UIApplication+{
++++class+func+topViewController(base:+UIViewController?+=+UIApplication.shared.keyWindow?.rootViewController)+->+UIViewController?+{
++++++++if+let+nav+=+base+as?+UINavigationController+{
++++++++++++return+topViewController(base:+nav.visibleViewController)
++++++++}
++++++++if+let+tab+=+base+as?+UITabBarController+{
++++++++++++if+let+selected+=+tab.selectedViewController+{
++++++++++++++++return+topViewController(base:+selected)
++++++++++++}
++++++++}
++++++++if+let+presented+=+base?.presentedViewController+{
++++++++++++return+topViewController(base:+presented)
++++++++}
++++++++return+base
++++}
}|code-block|syntax|javascript|2722925|不过用法仍然是一样的：|2722926|if+let+topController+=+UIApplication.topViewController()+{
++++print("The+view+controller+you're+looking+at+is:+\(topController)")
}|2722927|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/30858591/1478580^0|4|F|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|10|8|@]|9|@]|C|$G|H]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

I loved <a href="https://stackoverflow.com/a/30858591/1478580">@dianz's answer</a>, and so here is the swift 3's version of it. It's basically the same thing but his was missing a curly brace and some of the syntax/variable/method names have changed. So here it is!

<pre><code>extension UIApplication {
 class func topViewController(base: UIViewController? = UIApplication.shared.keyWindow?.rootViewController) -&gt; UIViewController? {
 if let nav = base as? UINavigationController {
 return topViewController(base: nav.visibleViewController)
 }
 if let tab = base as? UITabBarController {
 if let selected = tab.selectedViewController {
 return topViewController(base: selected)
 }
 }
 if let presented = base?.presentedViewController {
 return topViewController(base: presented)
 }
 return base
 }
}
</code></pre>

Usage is still the exact same though:

<pre><code>if let topController = UIApplication.topViewController() {
 print("The view controller you're looking at is: \(topController)")
}
</code></pre>

blocks|key|2935165|text|您可以在AppDelegate中定义一个UIViewController变量，并在每个viewWillAppear中将该变量设置为self(不过dianz答案是最好的答案)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2935166|override+func+viewWillAppear(animated:+Bool)+{
++++super.viewWillAppear(animated)
++++let+appDel+=+UIApplication.sharedApplication().delegate+as!+AppDelegate
++++appDel.currentVC+=+self
}|code-block|syntax|javascript|2935167|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

you can define a UIViewController variable in AppDelegate, and in every viewWillAppear set the variable to self.(however dianz answer is the best answer.)

<pre><code>override func viewWillAppear(animated: Bool) {
 super.viewWillAppear(animated)
 let appDel = UIApplication.sharedApplication().delegate as! AppDelegate
 appDel.currentVC = self
}
</code></pre>

blocks|key|2722962|text|在Swift+3中查找可见viewController|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2722963|if+let+viewControllers+=+window?.rootViewController?.childViewControllers+{

+++++let+prefs+=+UserDefaults.standard

+++++if+viewControllers[viewControllers.count+-+1]+is+ABCController{
++++++++print("[ABCController]+is+visible")

+++++}
}|code-block|syntax|javascript|2722964|此代码查找最后添加的控制器或最后可见的活动控制器。|2722965|这是我在AppDelegate中用来查找活动视图控制器的|2722966|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

To find the visible viewController in Swift 3

<pre><code>if let viewControllers = window?.rootViewController?.childViewControllers {

 let prefs = UserDefaults.standard

 if viewControllers[viewControllers.count - 1] is ABCController{
 print("[ABCController] is visible")

 }
}
</code></pre>

This code find the last added or the last active controller visible.

This I have used in AppDelegate to find active view Controller

blocks|key|146254|text|基于上面的Bob+-c：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|146255|Swift+3.0|offset|length|style|BOLD|146256|extension+UIWindow+{


++++func+visibleViewController()+->+UIViewController?+{
++++++++if+let+rootViewController:+UIViewController++=+self.rootViewController+{
++++++++++++return+UIWindow.getVisibleViewControllerFrom(vc:+rootViewController)
++++++++}
++++++++return+nil
++++}

++++class+func+getVisibleViewControllerFrom(vc:UIViewController)+->+UIViewController+{

++++++++if+vc.isKind(of:+UINavigationController.self)+{

++++++++++++let+navigationController+=+vc+as!+UINavigationController
++++++++++++return+UIWindow.getVisibleViewControllerFrom(+vc:+navigationController.visibleViewController!)

++++++++}+else+if+vc.isKind(of:+UITabBarController.self)+{

++++++++++++let+tabBarController+=+vc+as!+UITabBarController
++++++++++++return+UIWindow.getVisibleViewControllerFrom(vc:+tabBarController.selectedViewController!)

++++++++}+else+{

++++++++++++if+let+presentedViewController+=+vc.presentedViewController+{

++++++++++++++++return+UIWindow.getVisibleViewControllerFrom(vc:+presentedViewController)

++++++++++++}+else+{

++++++++++++++++return+vc;
++++++++++++}
++++++++}
++++}
}|code-block|syntax|javascript|146257|entityMap^0|0|0|9|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@$D|Q|E|R|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|S|8|@]|9|@]|A|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Based on Bob -c above: 

Swift 3.0

<pre><code>extension UIWindow {


 func visibleViewController() -&gt; UIViewController? {
 if let rootViewController: UIViewController = self.rootViewController {
 return UIWindow.getVisibleViewControllerFrom(vc: rootViewController)
 }
 return nil
 }

 class func getVisibleViewControllerFrom(vc:UIViewController) -&gt; UIViewController {

 if vc.isKind(of: UINavigationController.self) {

 let navigationController = vc as! UINavigationController
 return UIWindow.getVisibleViewControllerFrom( vc: navigationController.visibleViewController!)

 } else if vc.isKind(of: UITabBarController.self) {

 let tabBarController = vc as! UITabBarController
 return UIWindow.getVisibleViewControllerFrom(vc: tabBarController.selectedViewController!)

 } else {

 if let presentedViewController = vc.presentedViewController {

 return UIWindow.getVisibleViewControllerFrom(vc: presentedViewController)

 } else {

 return vc;
 }
 }
 }
}
</code></pre>

blocks|key|143915|text|使用此代码查找最顶层的UIViewController|type|unstyled|depth|inlineStyleRanges|entityRanges|data|143916|func+getTopViewController()+->+UIViewController?+{
++++var+topController:+UIViewController?+=+UIApplication.shared.keyWindow?.rootViewController
++++while+topController?.presentedViewController+!=+nil+{
++++++++topController+=+topController?.presentedViewController
++++}
++++return+topController
}|code-block|syntax|javascript|143917|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Use this code to find top most UIViewController

<pre><code>func getTopViewController() -&gt; UIViewController? {
 var topController: UIViewController? = UIApplication.shared.keyWindow?.rootViewController
 while topController?.presentedViewController != nil {
 topController = topController?.presentedViewController
 }
 return topController
}
</code></pre>

blocks|key|143919|text|适用于swift+4/5%2B的，可获得最高的viewController|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|143920|//+MARK:+UIApplication+extensions

extension+UIApplication+{

++++class+func+getTopViewController(base:+UIViewController?+=+UIApplication.shared.keyWindow?.rootViewController)+->+UIViewController?+{

++++++++if+let+nav+=+base+as?+UINavigationController+{
++++++++++++return+getTopViewController(base:+nav.visibleViewController)

++++++++}+else+if+let+tab+=+base+as?+UITabBarController,+let+selected+=+tab.selectedViewController+{
++++++++++++return+getTopViewController(base:+selected)

++++++++}+else+if+let+presented+=+base?.presentedViewController+{
++++++++++++return+getTopViewController(base:+presented)
++++++++}
++++++++return+base
++++}
}|code-block|syntax|javascript|143921|如何使用|143922|if+let+topVC+=+UIApplication.getTopViewController()+{
+++topVC.view.addSubview(forgotPwdView)
}|143923|entityMap^0|E|L|0|0|0|4|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|P|$]]

For swift 4 / 5 + to get topmost viewController

<pre><code>// MARK: UIApplication extensions

extension UIApplication {

 class func getTopViewController(base: UIViewController? = UIApplication.shared.keyWindow?.rootViewController) -&gt; UIViewController? {

 if let nav = base as? UINavigationController {
 return getTopViewController(base: nav.visibleViewController)

 } else if let tab = base as? UITabBarController, let selected = tab.selectedViewController {
 return getTopViewController(base: selected)

 } else if let presented = base?.presentedViewController {
 return getTopViewController(base: presented)
 }
 return base
 }
}
</code></pre>

How to use

<pre><code>if let topVC = UIApplication.getTopViewController() {
 topVC.view.addSubview(forgotPwdView)
}
</code></pre>

blocks|key|147780|text|https://gist.github.com/db0company/369bfa43cb84b145dfd8我对这个网站上的答案和评论做了一些测试。对我来说，下面的方法是可行的|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|147781|extension+UIViewController+{
++++func+topMostViewController()+->+UIViewController+{

++++++++if+let+presented+=+self.presentedViewController+{
++++++++++++return+presented.topMostViewController()
++++++++}

++++++++if+let+navigation+=+self+as?+UINavigationController+{
++++++++++++return+navigation.visibleViewController?.topMostViewController()+??+navigation
++++++++}

++++++++if+let+tab+=+self+as?+UITabBarController+{
++++++++++++return+tab.selectedViewController?.topMostViewController()+??+tab
++++}

++++++++return+self
++++}
}

extension+UIApplication+{
++++func+topMostViewController()+->+UIViewController?+{
++++++++return+self.keyWindow?.rootViewController?.topMostViewController()
++++}
}|code-block|syntax|javascript|147782|然后，通过以下方式获取顶级viewController：|147783|UIApplication.shared.topMostViewController()|147784|entityMap|0|LINK|mutability|MUTABLE|url|https://gist.github.com/db0company/369bfa43cb84b145dfd8^0|0|1J|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|10|8|@]|9|@]|C|$G|H]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

<a href="https://gist.github.com/db0company/369bfa43cb84b145dfd8" rel="noreferrer">https://gist.github.com/db0company/369bfa43cb84b145dfd8</a>
I did some tests on the answers and comments on this site. For me, the following works

<pre><code>extension UIViewController {
 func topMostViewController() -&gt; UIViewController {

 if let presented = self.presentedViewController {
 return presented.topMostViewController()
 }

 if let navigation = self as? UINavigationController {
 return navigation.visibleViewController?.topMostViewController() ?? navigation
 }

 if let tab = self as? UITabBarController {
 return tab.selectedViewController?.topMostViewController() ?? tab
 }

 return self
 }
}

extension UIApplication {
 func topMostViewController() -&gt; UIViewController? {
 return self.keyWindow?.rootViewController?.topMostViewController()
 }
}
</code></pre>

Then, get the top viewController by:

<pre><code>UIApplication.shared.topMostViewController()
</code></pre>

blocks|key|147796|text|@AlberZou使用计算变量而不是函数的细微变化|type|unstyled|depth|inlineStyleRanges|entityRanges|data|147797|extension+UIViewController+{
++var+topMostViewController+:+UIViewController+{

++++if+let+presented+=+self.presentedViewController+{
++++++return+presented.topMostViewController
++++}

++++if+let+navigation+=+self+as?+UINavigationController+{
++++++return+navigation.visibleViewController?.topMostViewController+??+navigation
++++}

++++if+let+tab+=+self+as?+UITabBarController+{
++++++return+tab.selectedViewController?.topMostViewController+??+tab
++++}

++++return+self
++}
}

extension+UIApplication+{
++var+topMostViewController+:+UIViewController?+{
++++return+self.keyWindow?.rootViewController?.topMostViewController
++}
}|code-block|syntax|javascript|147798|然后说|147799|if+let+topViewControler+=+UIApplication.shared.topMostViewController+{
++++...+do+stuff
}|147800|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Slight Variation on @AlberZou using a computed variable rather than a function

<pre><code>extension UIViewController {
 var topMostViewController : UIViewController {

 if let presented = self.presentedViewController {
 return presented.topMostViewController
 }

 if let navigation = self as? UINavigationController {
 return navigation.visibleViewController?.topMostViewController ?? navigation
 }

 if let tab = self as? UITabBarController {
 return tab.selectedViewController?.topMostViewController ?? tab
 }

 return self
 }
}

extension UIApplication {
 var topMostViewController : UIViewController? {
 return self.keyWindow?.rootViewController?.topMostViewController
 }
}
</code></pre>

Then say

<pre><code>if let topViewControler = UIApplication.shared.topMostViewController {
 ... do stuff
}
</code></pre>

blocks|key|2935298|text|在极少数情况下，使用自定义段，最上面的视图控制器不在导航堆栈或选项卡栏控制器中，也不显示，但它的视图被插入到关键窗口的子视图的顶部。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2935299|在这种情况下，有必要检查是否为UIApplication.shared.keyWindow.subviews.last+==+self.view，以确定当前的视图控制器是否是最顶部的。|offset|length|style|CODE|2935300|entityMap^0|0|F|1L|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

In a very rare case, with custom segue, the top most view controller is not in a navigation stack or tab bar controller or presented, but its view is inserted to the top of key windown's subviews. 

In such situation, it's necessary to check if <code>UIApplication.shared.keyWindow.subviews.last == self.view</code> to determine if the current view controller is the top most.

blocks|key|2935302|text|有太多的风格，但没有一个是反复阐述的。从前面几个组合而来：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2935303|+++++func+topMostController()+->+UIViewController?+{
++++++++var+from+=+UIApplication.shared.keyWindow?.rootViewController
++++++++while+(from+!=+nil)+{
++++++++++++if+let+to+=+(from+as?+UITabBarController)?.selectedViewController+{
++++++++++++++++from+=+to
++++++++++++}+else+if+let+to+=+(from+as?+UINavigationController)?.visibleViewController+{
++++++++++++++++from+=+to
++++++++++++}+else+if+let+to+=+from?.presentedViewController+{
++++++++++++++++from+=+to
++++++++++++}+else+{
++++++++++++++++break
++++++++++++}
++++++++}
++++++++return+from
++++}|code-block|syntax|javascript|2935304|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Too many flavours but none an iterative elaborated one. Combined from the previous ones:

<pre class="lang-swift prettyprint-override"><code> func topMostController() -&gt; UIViewController? {
 var from = UIApplication.shared.keyWindow?.rootViewController
 while (from != nil) {
 if let to = (from as? UITabBarController)?.selectedViewController {
 from = to
 } else if let to = (from as? UINavigationController)?.visibleViewController {
 from = to
 } else if let to = from?.presentedViewController {
 from = to
 } else {
 break
 }
 }
 return from
 }
</code></pre>

blocks|key|2935309|text|++var+topViewController:+UIViewController?+{
++++++++guard+var+topViewController+=+UIApplication.shared.keyWindow?.rootViewController+else+{+return+nil+}
++++++++while+let+presentedViewController+=+topViewController.presentedViewController+{
++++++++++++topViewController+=+presentedViewController
++++++++}
++++++++return+topViewController
++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2935310|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code> var topViewController: UIViewController? {
 guard var topViewController = UIApplication.shared.keyWindow?.rootViewController else { return nil }
 while let presentedViewController = topViewController.presentedViewController {
 topViewController = presentedViewController
 }
 return topViewController
 }
</code></pre>

blocks|key|145310|text|对我来说，最好的解决方案是一个带有函数的扩展。创建一个带有此扩展名的swift文件|type|unstyled|depth|inlineStyleRanges|entityRanges|data|145311|首先是UIWindow扩展：|offset|length|style|BOLD|145312|public+extension+UIWindow+{
++++var+visibleViewController:+UIViewController?+{
++++++++return+UIWindow.visibleVC(vc:+self.rootViewController)
++++}

++++static+func+visibleVC(vc:+UIViewController?)+->+UIViewController?+{
++++++++if+let+navigationViewController+=+vc+as?+UINavigationController+{
++++++++++++return+UIWindow.visibleVC(vc:+navigationViewController.visibleViewController)
++++++++}+else+if+let+tabBarVC+=+vc+as?+UITabBarController+{
++++++++++++return+UIWindow.visibleVC(vc:+tabBarVC.selectedViewController)
++++++++}+else+{
++++++++++++if+let+presentedVC+=+vc?.presentedViewController+{
++++++++++++++++return+UIWindow.visibleVC(vc:+presentedVC)
++++++++++++}+else+{
++++++++++++++++return+vc
++++++++++++}
++++++++}
++++}
}|code-block|syntax|javascript|145313|在文件添加函数内部|145314|func+visibleViewController()+->+UIViewController?+{
++++let+appDelegate+=+UIApplication.shared.delegate
++++if+let+window+=+appDelegate!.window+{
++++++++return+window?.visibleViewController
++++}
++++return+nil
}|145315|如果你想使用它，你可以在任何地方调用它。示例：|145316|++override+func+viewDidLoad()+{
++++super.viewDidLoad()
++++++if+let+topVC+=+visibleViewController()+{
+++++++++++++//show+some+label+or+text+field+
++++}
}|145317|文件代码类似于下面的：|145318|import+UIKit

public+extension+UIWindow+{
++++var+visibleViewController:+UIViewController?+{
++++++++return+UIWindow.visibleVC(vc:+self.rootViewController)
++++}

++++static+func+visibleVC(vc:+UIViewController?)+->+UIViewController?+{
++++++++if+let+navigationViewController+=+vc+as?+UINavigationController+{
++++++++++++return+UIWindow.visibleVC(vc:+navigationViewController.visibleViewController)
++++++++}+else+if+let+tabBarVC+=+vc+as?+UITabBarController+{
++++++++++++return+UIWindow.visibleVC(vc:+tabBarVC.selectedViewController)
++++++++}+else+{
++++++++++++if+let+presentedVC+=+vc?.presentedViewController+{
++++++++++++++++return+UIWindow.visibleVC(vc:+presentedVC)
++++++++++++}+else+{
++++++++++++++++return+vc
++++++++++++}
++++++++}
++++}
}

func+visibleViewController()+->+UIViewController?+{
++++let+appDelegate+=+UIApplication.shared.delegate
++++if+let+window+=+appDelegate!.window+{
++++++++return+window?.visibleViewController
++++}
++++return+nil
}|145319|entityMap^0|0|0|D|0|0|0|0|K|2|0|0|0|A|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@$D|12|E|13|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|14|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|15|8|@]|9|@]|A|$]]|$1|O|3|P|5|J|7|16|8|@]|9|@]|A|$K|L]]|$1|Q|3|R|5|6|7|17|8|@$D|18|E|19|F|G]]|9|@]|A|$]]|$1|S|3|T|5|J|7|1A|8|@]|9|@]|A|$K|L]]|$1|U|3|V|5|6|7|1B|8|@$D|1C|E|1D|F|G]]|9|@]|A|$]]|$1|W|3|X|5|J|7|1E|8|@]|9|@]|A|$K|L]]|$1|Y|3|-4|5|6|7|1F|8|@]|9|@]|A|$]]]|Z|$]]

The best solution for me is an extension with a function. 
Create a swift file with this extension

First is the UIWindow extension: 

<pre><code>public extension UIWindow {
 var visibleViewController: UIViewController? {
 return UIWindow.visibleVC(vc: self.rootViewController)
 }

 static func visibleVC(vc: UIViewController?) -&gt; UIViewController? {
 if let navigationViewController = vc as? UINavigationController {
 return UIWindow.visibleVC(vc: navigationViewController.visibleViewController)
 } else if let tabBarVC = vc as? UITabBarController {
 return UIWindow.visibleVC(vc: tabBarVC.selectedViewController)
 } else {
 if let presentedVC = vc?.presentedViewController {
 return UIWindow.visibleVC(vc: presentedVC)
 } else {
 return vc
 }
 }
 }
}
</code></pre>

inside that file add function

<pre><code>func visibleViewController() -&gt; UIViewController? {
 let appDelegate = UIApplication.shared.delegate
 if let window = appDelegate!.window {
 return window?.visibleViewController
 }
 return nil
}
</code></pre>

And if you want to use it, you can call it anywhere. 
Example: 

<pre><code> override func viewDidLoad() {
 super.viewDidLoad()
 if let topVC = visibleViewController() {
 //show some label or text field 
 }
}
</code></pre>

File code is like this: 

<pre><code>import UIKit

public extension UIWindow {
 var visibleViewController: UIViewController? {
 return UIWindow.visibleVC(vc: self.rootViewController)
 }

 static func visibleVC(vc: UIViewController?) -&gt; UIViewController? {
 if let navigationViewController = vc as? UINavigationController {
 return UIWindow.visibleVC(vc: navigationViewController.visibleViewController)
 } else if let tabBarVC = vc as? UITabBarController {
 return UIWindow.visibleVC(vc: tabBarVC.selectedViewController)
 } else {
 if let presentedVC = vc?.presentedViewController {
 return UIWindow.visibleVC(vc: presentedVC)
 } else {
 return vc
 }
 }
 }
}

func visibleViewController() -&gt; UIViewController? {
 let appDelegate = UIApplication.shared.delegate
 if let window = appDelegate!.window {
 return window?.visibleViewController
 }
 return nil
}
</code></pre>

blocks|key|2723118|text|import+UIKit

extension+UIApplication+{

++++//+MARK:+Choose+keyWindow+as+per+your+choice
++++var+currentWindow:+UIWindow?+{
++++++++connectedScenes
++++++++.filter({$0.activationState+==+.foregroundActive})
++++++++.map({$0+as?+UIWindowScene})
++++++++.compactMap({$0})
++++++++.first?.windows
++++++++.filter({$0.isKeyWindow}).first
++++}

++++//+MARK:+Choose+keyWindow+as+per+your+choice
++++var+keyWindow:+UIWindow?+{
++++++++UIApplication.shared.windows.first+{+$0.isKeyWindow+}
++++}

++++class+func+topMostViewController(base:+UIViewController?+=+UIApplication.shared.currentWindow?.rootViewController)+->+UIViewController?+{

++++++++if+let+nav+=+base+as?+UINavigationController+{
++++++++++++return+topMostViewController(base:+nav.visibleViewController)
++++++++}

++++++++if+let+tab+=+base+as?+UITabBarController+{
++++++++++++let+moreNavigationController+=+tab.moreNavigationController

++++++++++++if+let+top+=+moreNavigationController.topViewController,+top.view.window+!=+nil+{
++++++++++++++++return+topMostViewController(base:+top)
++++++++++++}+else+if+let+selected+=+tab.selectedViewController+{
++++++++++++++++return+topMostViewController(base:+selected)
++++++++++++}
++++++++}
++++++++if+let+presented+=+base?.presentedViewController+{
++++++++++++return+topMostViewController(base:+presented)
++++++++}
++++++++return+base
++++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2723119|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>import UIKit

extension UIApplication {

 // MARK: Choose keyWindow as per your choice
 var currentWindow: UIWindow? {
 connectedScenes
 .filter({$0.activationState == .foregroundActive})
 .map({$0 as? UIWindowScene})
 .compactMap({$0})
 .first?.windows
 .filter({$0.isKeyWindow}).first
 }

 // MARK: Choose keyWindow as per your choice
 var keyWindow: UIWindow? {
 UIApplication.shared.windows.first { $0.isKeyWindow }
 }

 class func topMostViewController(base: UIViewController? = UIApplication.shared.currentWindow?.rootViewController) -&gt; UIViewController? {

 if let nav = base as? UINavigationController {
 return topMostViewController(base: nav.visibleViewController)
 }

 if let tab = base as? UITabBarController {
 let moreNavigationController = tab.moreNavigationController

 if let top = moreNavigationController.topViewController, top.view.window != nil {
 return topMostViewController(base: top)
 } else if let selected = tab.selectedViewController {
 return topMostViewController(base: selected)
 }
 }
 if let presented = base?.presentedViewController {
 return topMostViewController(base: presented)
 }
 return base
 }
}
</code></pre>

blocks|key|2723159|text|适用于寻求快速5/iOS+13%2B解决方案的任何人(从iOS+13开始就不再推荐使用keywindow)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2723160|extension+UIApplication+{

++++class+func+getTopMostViewController()+->+UIViewController?+{
++++++++let+keyWindow+=+UIApplication.shared.windows.filter+{$0.isKeyWindow}.first
++++++++if+var+topController+=+keyWindow?.rootViewController+{
++++++++++++while+let+presentedViewController+=+topController.presentedViewController+{
++++++++++++++++topController+=+presentedViewController
++++++++++++}
++++++++++++return+topController
++++++++}+else+{
++++++++++++return+nil
++++++++}
++++}
}|code-block|syntax|javascript|2723161|entityMap^0|15|9|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

For anyone looking for a swift 5/iOS 13+ solution (<code>keywindow</code> is deprecated since iOS 13)

<pre><code>extension UIApplication {

 class func getTopMostViewController() -&gt; UIViewController? {
 let keyWindow = UIApplication.shared.windows.filter {$0.isKeyWindow}.first
 if var topController = keyWindow?.rootViewController {
 while let presentedViewController = topController.presentedViewController {
 topController = presentedViewController
 }
 return topController
 } else {
 return nil
 }
 }
}
</code></pre>

blocks|key|2935357|text|extension+UIViewController+{
++++func+topMostViewController()+->+UIViewController+{
++++++++if+self.presentedViewController+==+nil+{
++++++++++++return+self
++++++++}
++++++++if+let+navigation+=+self.presentedViewController+as?+UINavigationController+{
++++++++++++return+navigation.visibleViewController.topMostViewController()
++++++++}
++++++++if+let+tab+=+self.presentedViewController+as?+UITabBarController+{
++++++++++++if+let+selectedTab+=+tab.selectedViewController+{
++++++++++++++++return+selectedTab.topMostViewController()
++++++++++++}
++++++++++++return+tab.topMostViewController()
++++++++}
++++++++return+self.presentedViewController!.topMostViewController()
++++}
}

extension+UIApplication+{
++++func+topMostViewController()+->+UIViewController?+{
++++++++return+self.keyWindow?.rootViewController?.topMostViewController()
++++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2935358|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>extension UIViewController {
 func topMostViewController() -&gt; UIViewController {
 if self.presentedViewController == nil {
 return self
 }
 if let navigation = self.presentedViewController as? UINavigationController {
 return navigation.visibleViewController.topMostViewController()
 }
 if let tab = self.presentedViewController as? UITabBarController {
 if let selectedTab = tab.selectedViewController {
 return selectedTab.topMostViewController()
 }
 return tab.topMostViewController()
 }
 return self.presentedViewController!.topMostViewController()
 }
}

extension UIApplication {
 func topMostViewController() -&gt; UIViewController? {
 return self.keyWindow?.rootViewController?.topMostViewController()
 }
}
</code></pre>

blocks|key|2723186|text|对于Swift+5%2B，iOS+13%2B|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|2723187|extension+UIViewController+{
++++static+func+topMostViewController()+->+UIViewController?+{
++++++++if+#available(iOS+13.0,+*)+{
++++++++++++let+keyWindow+=+UIApplication.shared.windows.filter+{$0.isKeyWindow}.first
++++++++++++return+keyWindow?.rootViewController?.topMostViewController()
++++++++}
++++++++
++++++++return+UIApplication.shared.keyWindow?.rootViewController?.topMostViewController()
++++}
++++
++++func+topMostViewController()+->+UIViewController?+{
++++++++if+let+navigationController+=+self+as?+UINavigationController+{
++++++++++++return+navigationController.topViewController?.topMostViewController()
++++++++}
++++++++else+if+let+tabBarController+=+self+as?+UITabBarController+{
++++++++++++if+let+selectedViewController+=+tabBarController.selectedViewController+{
++++++++++++++++return+selectedViewController.topMostViewController()
++++++++++++}
++++++++++++return+tabBarController.topMostViewController()
++++++++}
++++++++++++
++++++++else+if+let+presentedViewController+=+self.presentedViewController+{
++++++++++++return+presentedViewController.topMostViewController()
++++++++}
++++++++
++++++++else+{
++++++++++++return+self
++++++++}
++++}
}|code-block|syntax|javascript|2723188|使用：|2723189|在没有UIViewController实例的情况下获取topMostViewController时|2723190|guard+let+viewController+=+UIViewController.topMostViewController()+else+{+return+}
print(viewController)|2723191|获取UIViewController实例的topMostViewController时|2723192|let+yourVC+=+UIViewController()
guard+let+vc+=+yourVC.topMostViewController()+else+{+return+}
print(vc)|2723193|entityMap^0|2|8|B|7|0|0|0|3|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|15|8|@]|D|@]|E|$]]|$1|O|3|P|5|H|7|16|8|@]|D|@]|E|$I|J]]|$1|Q|3|R|5|6|7|17|8|@]|D|@]|E|$]]|$1|S|3|T|5|H|7|18|8|@]|D|@]|E|$I|J]]|$1|U|3|-4|5|6|7|19|8|@]|D|@]|E|$]]]|V|$]]

For Swift 5+,
iOS 13+
<pre><code>extension UIViewController {
 static func topMostViewController() -&gt; UIViewController? {
 if #available(iOS 13.0, *) {
 let keyWindow = UIApplication.shared.windows.filter {$0.isKeyWindow}.first
 return keyWindow?.rootViewController?.topMostViewController()
 }
 
 return UIApplication.shared.keyWindow?.rootViewController?.topMostViewController()
 }
 
 func topMostViewController() -&gt; UIViewController? {
 if let navigationController = self as? UINavigationController {
 return navigationController.topViewController?.topMostViewController()
 }
 else if let tabBarController = self as? UITabBarController {
 if let selectedViewController = tabBarController.selectedViewController {
 return selectedViewController.topMostViewController()
 }
 return tabBarController.topMostViewController()
 }
 
 else if let presentedViewController = self.presentedViewController {
 return presentedViewController.topMostViewController()
 }
 
 else {
 return self
 }
 }
}
</code></pre>
Usage:
When you are getting topMostViewController without instance of UIViewController
<pre><code>guard let viewController = UIViewController.topMostViewController() else { return }
print(viewController)
</code></pre>
When you are getting topMostViewController of instance of UIViewController
<pre><code>let yourVC = UIViewController()
guard let vc = yourVC.topMostViewController() else { return }
print(vc)
</code></pre>

blocks|key|147897|text|class+func+topViewController(controller:+UIViewController?+=+UIApplication.shared.keyWindow?.rootViewController)+->+UIViewController?+{
++++++++if+let+navigationController+=+controller+as?+UINavigationController+{
++++++++++++return+topViewController(controller:+navigationController.visibleViewController)
++++++++}
++++++++if+let+tabController+=+controller+as?+UITabBarController+{
++++++++++++if+let+selected+=+tabController.selectedViewController+{
++++++++++++++++return+topViewController(controller:+selected)
++++++++++++}
++++++++}
++++++++if+let+presented+=+controller?.presentedViewController+{
++++++++++++return+topViewController(controller:+presented)
++++++++}
++++++++return+controller
++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|147898|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>class func topViewController(controller: UIViewController? = UIApplication.shared.keyWindow?.rootViewController) -&gt; UIViewController? {
 if let navigationController = controller as? UINavigationController {
 return topViewController(controller: navigationController.visibleViewController)
 }
 if let tabController = controller as? UITabBarController {
 if let selected = tabController.selectedViewController {
 return topViewController(controller: selected)
 }
 }
 if let presented = controller?.presentedViewController {
 return topViewController(controller: presented)
 }
 return controller
 }
</code></pre>

blocks|key|144043|text|iOS13%2B+//最上面的视图控制器|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|144044|extension+UIViewController+{
++++func+topMostViewController()+->+UIViewController+{
++++++++if+self.presentedViewController+==+nil+{
++++++++++++return+self
++++++++}
++++++++if+let+navigation+=+self.presentedViewController+as?+UINavigationController+{
++++++++++++return+navigation.visibleViewController!.topMostViewController()
++++++++}
++++++++if+let+tab+=+self.presentedViewController+as?+UITabBarController+{
++++++++++++if+let+selectedTab+=+tab.selectedViewController+{
++++++++++++++++return+selectedTab.topMostViewController()
++++++++++++}
++++++++++++return+tab.topMostViewController()
++++++++}
++++++++return+self.presentedViewController!.topMostViewController()
++++}
}

extension+UIApplication+{
++++func+topMostViewController()+->+UIViewController?+{
++++++++return+UIWindow.key!.rootViewController?.topMostViewController()
++++}
}

extension+UIWindow+{
++++static+var+key:+UIWindow?+{
++++++++if+#available(iOS+13,+*)+{
++++++++++++return+UIApplication.shared.windows.first+{+$0.isKeyWindow+}
++++++++}+else+{
++++++++++++return+UIApplication.shared.keyWindow
++++++++}
++++}
}

//use+let+vc+=+UIApplication.shared.topMostViewController()

//+End+top+Most+view+Controller|code-block|syntax|javascript|144045|entityMap^0|0|6|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

iOS13+ //top Most view Controller
<pre><code>extension UIViewController {
 func topMostViewController() -&gt; UIViewController {
 if self.presentedViewController == nil {
 return self
 }
 if let navigation = self.presentedViewController as? UINavigationController {
 return navigation.visibleViewController!.topMostViewController()
 }
 if let tab = self.presentedViewController as? UITabBarController {
 if let selectedTab = tab.selectedViewController {
 return selectedTab.topMostViewController()
 }
 return tab.topMostViewController()
 }
 return self.presentedViewController!.topMostViewController()
 }
}

extension UIApplication {
 func topMostViewController() -&gt; UIViewController? {
 return UIWindow.key!.rootViewController?.topMostViewController()
 }
}

extension UIWindow {
 static var key: UIWindow? {
 if #available(iOS 13, *) {
 return UIApplication.shared.windows.first { $0.isKeyWindow }
 } else {
 return UIApplication.shared.keyWindow
 }
 }
}

//use let vc = UIApplication.shared.topMostViewController()

// End top Most view Controller
</code></pre>

blocks|key|2723226|text|在SWIFT+5.2中|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|2723227|你可以使用下面的代码：|2723228|import+UIKit

extension+UIWindow+{
++++static+func+getTopViewController()+->+UIViewController?+{
++++++++if+#available(iOS+13,+*){
++++++++++++let+keyWindow+=+UIApplication.shared.windows.filter+{$0.isKeyWindow}.first
++++++++++++
++++++++++++if+var+topController+=+keyWindow?.rootViewController+{
++++++++++++++++while+let+presentedViewController+=+topController.presentedViewController+{
++++++++++++++++++++topController+=+presentedViewController
++++++++++++++++}
++++++++++++++++return+topController
++++++++++++}
++++++++}+else+{
++++++++++++if+var+topController+=+UIApplication.shared.keyWindow?.rootViewController+{
++++++++++++++++while+let+presentedViewController+=+topController.presentedViewController+{
++++++++++++++++++++topController+=+presentedViewController
++++++++++++++++}
++++++++++++++++return+topController
++++++++++++}
++++++++}
++++++++return+nil
++++}
}|code-block|syntax|javascript|2723229|entityMap^0|1|9|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|S|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

in SWIFT 5.2
you can use underneath code:
<pre><code>import UIKit

extension UIWindow {
 static func getTopViewController() -&gt; UIViewController? {
 if #available(iOS 13, *){
 let keyWindow = UIApplication.shared.windows.filter {$0.isKeyWindow}.first
 
 if var topController = keyWindow?.rootViewController {
 while let presentedViewController = topController.presentedViewController {
 topController = presentedViewController
 }
 return topController
 }
 } else {
 if var topController = UIApplication.shared.keyWindow?.rootViewController {
 while let presentedViewController = topController.presentedViewController {
 topController = presentedViewController
 }
 return topController
 }
 }
 return nil
 }
}
</code></pre>

blocks|key|2723245|text|+extension+UIApplication+{
++++
++++public+var+mainKeyWindow:+UIWindow?+{
++++++++return+windows.first(where:+{+$0.isKeyWindow+})+??+keyWindow
++++}

++++public+var+rootViewController:+UIViewController?+{
++++++++guard+let+keyWindow+=+UIApplication.shared.mainKeyWindow,+let+rootViewController+=+keyWindow.rootViewController+else+{
++++++++++++return+nil
++++++++}
++++++++return+rootViewController
++++}

++++public+func+topViewController(controller:+UIViewController?+=+UIApplication.shared.rootViewController)+->+UIViewController?+{

++++++++if+controller+==+nil+{
++++++++++++return+topViewController(controller:+rootViewController)
++++++++}
++++++++
++++++++if+let+navigationController+=+controller+as?+UINavigationController+{
++++++++++++return+topViewController(controller:+navigationController.visibleViewController)
++++++++}

++++++++if+let+tabController+=+controller+as?+UITabBarController+{
++++++++++++if+let+selectedViewController+=+tabController.selectedViewController+{
++++++++++++++++return+topViewController(controller:+selectedViewController)
++++++++++++}
++++++++}

++++++++if+let+presentedViewController+=+controller?.presentedViewController+{
++++++++++++return+topViewController(controller:+presentedViewController)
++++++++}

++++++++return+controller
++++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2723246|Swift+5.2及更高版本|unstyled|offset|length|style|BOLD|2723247|entityMap^0|0|0|E|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|N|8|@$G|O|H|P|I|J]]|9|@]|A|$]]|$1|K|3|-4|5|F|7|Q|8|@]|9|@]|A|$]]]|L|$]]

<pre><code> extension UIApplication {
 
 public var mainKeyWindow: UIWindow? {
 return windows.first(where: { $0.isKeyWindow }) ?? keyWindow
 }

 public var rootViewController: UIViewController? {
 guard let keyWindow = UIApplication.shared.mainKeyWindow, let rootViewController = keyWindow.rootViewController else {
 return nil
 }
 return rootViewController
 }

 public func topViewController(controller: UIViewController? = UIApplication.shared.rootViewController) -&gt; UIViewController? {

 if controller == nil {
 return topViewController(controller: rootViewController)
 }
 
 if let navigationController = controller as? UINavigationController {
 return topViewController(controller: navigationController.visibleViewController)
 }

 if let tabController = controller as? UITabBarController {
 if let selectedViewController = tabController.selectedViewController {
 return topViewController(controller: selectedViewController)
 }
 }

 if let presentedViewController = controller?.presentedViewController {
 return topViewController(controller: presentedViewController)
 }

 return controller
 }
}
</code></pre>
Swift 5.2 and above

blocks|key|2935469|text|我使用以下代码来获取topViewController-|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2935470|它向后兼容旧的iOS版本，并支持UIScene+too|offset|length|style|BOLD|2935471|extension+UIApplication+{
++++func+topViewController()+->+UIViewController?+{
++++++++var+topViewController:+UIViewController?+=+nil
++++++++if+#available(iOS+13,+*)+{
++++++++++++for+scene+in+connectedScenes+{
++++++++++++++++if+let+windowScene+=+scene+as?+UIWindowScene+{
++++++++++++++++++++for+window+in+windowScene.windows+{
++++++++++++++++++++++++if+window.isKeyWindow+{
++++++++++++++++++++++++++++topViewController+=+window.rootViewController
++++++++++++++++++++++++}
++++++++++++++++++++}
++++++++++++++++}
++++++++++++}
++++++++}+else+{
++++++++++++topViewController+=+keyWindow?.rootViewController
++++++++}
++++++++while+true+{
++++++++++++if+let+presented+=+topViewController?.presentedViewController+{
++++++++++++++++topViewController+=+presented
++++++++++++}+else+if+let+navController+=+topViewController+as?+UINavigationController+{
++++++++++++++++topViewController+=+navController.topViewController
++++++++++++}+else+if+let+tabBarController+=+topViewController+as?+UITabBarController+{
++++++++++++++++topViewController+=+tabBarController.selectedViewController
++++++++++++}+else+{
++++++++++++++++//+Handle+any+other+third+party+container+in+`else+if`+if+required
++++++++++++++++break
++++++++++++}
++++++++}
++++++++return+topViewController
++++}
}|code-block|syntax|javascript|2935472|它可以这样使用：|2935473|let+topController+=+UIApplication.shared.topViewController()
topController?.present(controllerToPresent,+animated:+true,+completion:+nil)|2935474|entityMap^0|0|0|R|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@$D|U|E|V|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|W|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|J|7|Y|8|@]|9|@]|A|$K|L]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

I use the following code to get the topViewController-
It is backward compatible to older iOS versions &amp; takes care of UIScene too
<pre><code>extension UIApplication {
 func topViewController() -&gt; UIViewController? {
 var topViewController: UIViewController? = nil
 if #available(iOS 13, *) {
 for scene in connectedScenes {
 if let windowScene = scene as? UIWindowScene {
 for window in windowScene.windows {
 if window.isKeyWindow {
 topViewController = window.rootViewController
 }
 }
 }
 }
 } else {
 topViewController = keyWindow?.rootViewController
 }
 while true {
 if let presented = topViewController?.presentedViewController {
 topViewController = presented
 } else if let navController = topViewController as? UINavigationController {
 topViewController = navController.topViewController
 } else if let tabBarController = topViewController as? UITabBarController {
 topViewController = tabBarController.selectedViewController
 } else {
 // Handle any other third party container in `else if` if required
 break
 }
 }
 return topViewController
 }
}
</code></pre>
It could be used in this way:
<pre><code>let topController = UIApplication.shared.topViewController()
topController?.present(controllerToPresent, animated: true, completion: nil)
</code></pre>

blocks|key|2723341|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2723342|+Swift+5%2B|blockquote|2723343|2723344|2723345|声明|offset|length|style|BOLD|2723346|func+topViewController()+->+UIViewController?+{
++++
++++let+keyWindow+=+UIApplication.shared.windows.filter+{$0.isKeyWindow}.first

++++if+var+topController+=+keyWindow?.rootViewController+{
++++++++
++++++++while+let+presentedViewController+=+topController.presentedViewController+{
++++++++++++topController+=+presentedViewController
++++++++}
++++++++
++++++++return+topController
++++++++
++++}+else+{
++++++++
++++++++return+nil
++++++++
++++}
++++
}|code-block|syntax|javascript|2723347|使用的|2723348|topViewController()?.view.addSubview(UIView())|2723349|entityMap^0|0|0|0|0|0|2|0|0|0|0^^$0|@$1|2|3|-4|4|5|6|W|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|X|7|@]|8|@]|9|$]]|$1|D|3|-4|4|5|6|Y|7|@]|8|@]|9|$]]|$1|E|3|-4|4|5|6|Z|7|@]|8|@]|9|$]]|$1|F|3|G|4|5|6|10|7|@$H|11|I|12|J|K]]|8|@]|9|$]]|$1|L|3|M|4|N|6|13|7|@]|8|@]|9|$O|P]]|$1|Q|3|R|4|5|6|14|7|@]|8|@]|9|$]]|$1|S|3|T|4|N|6|15|7|@]|8|@]|9|$O|P]]|$1|U|3|-4|4|5|6|16|7|@]|8|@]|9|$]]]|V|$]]

<blockquote>
Swift 5+
</blockquote>
Declare
<pre><code>func topViewController() -&gt; UIViewController? {
 
 let keyWindow = UIApplication.shared.windows.filter {$0.isKeyWindow}.first

 if var topController = keyWindow?.rootViewController {
 
 while let presentedViewController = topController.presentedViewController {
 topController = presentedViewController
 }
 
 return topController
 
 } else {
 
 return nil
 
 }
 
}
</code></pre>
Use
<pre><code>topViewController()?.view.addSubview(UIView())
</code></pre>

I can't seem to get the top most <code>UIViewController</code> without access to a <code>UINavigationController</code>. Here is what I have so far:

<pre><code>UIApplication.sharedApplication().keyWindow?.rootViewController?.presentViewController(vc, animated: true, completion: nil)
</code></pre>

However, it does not seem to do anything. The <code>keyWindow</code> and <code>rootViewController</code> seem to be non-nil values too, so the optional chaining shouldn't be an issue.

NOTE: It is a bad idea to do something like this. It breaks the MVC pattern.

Get top most UIViewController

Objective-C

Swift

如果不访问UINavigationController，我似乎无法获得最高级别的UIViewController。这是我到目前为止所知道的：UIApplication.sharedApplication().keyWindow?.rootViewController?.presentViewController(vc,...

问获取最顶级的UIViewController
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