Get the current displaying UIViewController on the screen in AppDelegate.m

Question

The current UIViewController on the screen need to response to push-notifications from APNs, by setting some badge views. But how could I get the UIViewController in methodapplication:didReceiveRemoteNotification: of AppDelegate.m?

I tried use self.window.rootViewController to get the current displaying UIViewController, it may be a UINavigationViewController or some other kind of view controller. And I find out that the visibleViewController property of UINavigationViewController can be used to get the UIViewController on the screen. But what could I do if it is not a UINavigationViewController?

Any help is appreciated! The related code is as following.

AppDelegate.m

...
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo {

    //I would like to find out which view controller is on the screen here.

    UIViewController *vc = [(UINavigationViewController *)self.window.rootViewController visibleViewController];
    [vc performSelector:@selector(handleThePushNotification:) withObject:userInfo];
}
...

ViewControllerA.m

- (void)handleThePushNotification:(NSDictionary *)userInfo{

    //set some badge view here

}

Answer 1

I always love solutions that involve categories as they are bolt on and can be easily reused.

So I created a category on UIWindow. You can now call visibleViewController on UIWindow and this will get you the visible view controller by searching down the controller hierarchy. This works if you are using navigation and/or tab bar controller. If you have another type of controller to suggest please let me know and I can add it.

UIWindow+PazLabs.h (header file)

#import <UIKit/UIKit.h>

@interface UIWindow (PazLabs)

- (UIViewController *) visibleViewController;

@end

UIWindow+PazLabs.m (implementation file)

#import "UIWindow+PazLabs.h"

@implementation UIWindow (PazLabs)

- (UIViewController *)visibleViewController {
    UIViewController *rootViewController = self.rootViewController;
    return [UIWindow getVisibleViewControllerFrom:rootViewController];
}

+ (UIViewController *) getVisibleViewControllerFrom:(UIViewController *) vc {
    if ([vc isKindOfClass:[UINavigationController class]]) {
        return [UIWindow getVisibleViewControllerFrom:[((UINavigationController *) vc) visibleViewController]];
    } else if ([vc isKindOfClass:[UITabBarController class]]) {
        return [UIWindow getVisibleViewControllerFrom:[((UITabBarController *) vc) selectedViewController]];
    } else {
        if (vc.presentedViewController) {
            return [UIWindow getVisibleViewControllerFrom:vc.presentedViewController];
        } else {
            return vc;
        }
    }
}

@end

Swift Version

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

    public static func getVisibleViewControllerFrom(_ vc: UIViewController?) -> UIViewController? {
        if let nc = vc as? UINavigationController {
            return UIWindow.getVisibleViewControllerFrom(nc.visibleViewController)
        } else if let tc = vc as? UITabBarController {
            return UIWindow.getVisibleViewControllerFrom(tc.selectedViewController)
        } else {
            if let pvc = vc?.presentedViewController {
                return UIWindow.getVisibleViewControllerFrom(pvc)
            } else {
                return vc
            }
        }
    }
}

Answer 2

You can use the rootViewController also when your controller is not a UINavigationController:

UIViewController *vc = self.window.rootViewController;

Once you know the root view controller, then it depends on how you have built your UI, but you can possibly find out a way to navigate through the controllers hierarchy.

If you give some more details about the way you defined your app, then I might give some more hint.

EDIT:

If you want the topmost view (not view controller), you could check

[[[[UIApplication sharedApplication] keyWindow] subviews] lastObject];

although this view might be invisible or even covered by some of its subviews...

again, it depends on your UI, but this might help...

Answer 3

Simple extension for UIApplication in Swift (cares even about moreNavigationController within UITabBarController on iPhone):

extension UIApplication {
    class func topViewController(base: UIViewController? = UIApplication.sharedApplication().keyWindow?.rootViewController) -> UIViewController? {

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

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

            if let top = moreNavigationController.topViewController where top.view.window != nil {
                return topViewController(top)
            } else if let selected = tab.selectedViewController {
                return topViewController(selected)
            }
        }

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

        return base
    }
}

Simple usage:

    if let rootViewController = UIApplication.topViewController() {
        //do sth with root view controller
    }

Works perfect:-)

UPDATE for clean code:

extension UIViewController {
    var top: UIViewController? {
        if let controller = self as? UINavigationController {
            return controller.topViewController?.top
        }
        if let controller = self as? UISplitViewController {
            return controller.viewControllers.last?.top
        }
        if let controller = self as? UITabBarController {
            return controller.selectedViewController?.top
        }
        if let controller = presentedViewController {
            return controller.top
        }
        return self
    }
}

Answer 4

You could also post a notification via NSNotificationCenter. This let's you deal with a number of situations where traversing the view controller hierarchy might be tricky - for example when modals are being presented, etc.

E.g.,

// MyAppDelegate.h
NSString * const UIApplicationDidReceiveRemoteNotification;

// MyAppDelegate.m
NSString * const UIApplicationDidReceiveRemoteNotification = @"UIApplicationDidReceiveRemoteNotification";

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo {

    [[NSNotificationCenter defaultCenter]
     postNotificationName:UIApplicationDidReceiveRemoteNotification
     object:self
     userInfo:userInfo];
}

In each of your View Controllers:

-(void)viewDidLoad {
    [[NSNotificationCenter defaultCenter] 
      addObserver:self
      selector:@selector(didReceiveRemoteNotification:)                                                  
      name:UIApplicationDidReceiveRemoteNotification
      object:nil];
}

-(void)viewDidUnload {
    [[NSNotificationCenter defaultCenter] 
      removeObserver:self
      name:UIApplicationDidReceiveRemoteNotification
      object:nil];
}

-(void)didReceiveRemoteNotification:(NSDictionary *)userInfo {
    // see http://stackoverflow.com/a/2777460/305149
   if (self.isViewLoaded && self.view.window) {
      // handle the notification
   }
}

You could also use this approach to instrument controls which need to update when a notification is received and are used by several view controllers. In that case, handle the add/remove observer calls in the init and dealloc methods, respectively.

Answer 5

Code

Here's an approach using the great switch-case syntax in Swift 3/4/5:

import UIKit

extension UIWindow {
    /// Returns the currently visible view controller if any reachable within the window.
    public var visibleViewController: UIViewController? {
        return UIWindow.visibleViewController(from: rootViewController)
    }

    /// Recursively follows navigation controllers, tab bar controllers and modal presented view controllers starting
    /// from the given view controller to find the currently visible view controller.
    ///
    /// - Parameters:
    ///   - viewController: The view controller to start the recursive search from.
    /// - Returns: The view controller that is most probably visible on screen right now.
    public static func visibleViewController(from viewController: UIViewController?) -> UIViewController? {
        switch viewController {
        case let navigationController as UINavigationController:
            return UIWindow.visibleViewController(from: navigationController.visibleViewController ?? navigationController.topViewController)

        case let tabBarController as UITabBarController:
            return UIWindow.visibleViewController(from: tabBarController.selectedViewController)

        case let presentingViewController where viewController?.presentedViewController != nil:
            return UIWindow.visibleViewController(from: presentingViewController?.presentedViewController)

        default:
            return viewController
        }
    }
}

The basic idea is the same as in zirinisp's answer, it's just using a more Swift 3+ like syntax.

---

Usage

You probably want to create a file named UIWindowExt.swift and copy the above extension code into it.

On the call side it can be either used without any specific view controller:

if let visibleViewCtrl = UIApplication.shared.keyWindow?.visibleViewController {
    // do whatever you want with your `visibleViewCtrl`
}

Or if you know your visible view controller is reachable from a specific view controller:

if let visibleViewCtrl = UIWindow.visibleViewController(from: specificViewCtrl) {
    // do whatever you want with your `visibleViewCtrl`
}

I hope it helps!

Answer 6

I have found that iOS 8 has screwed everything up. In iOS 7 there is a new UITransitionView on the view hierarchy whenever you have a modally presented UINavigationController. Anyway, here's my code that finds gets the topmost VC. Calling getTopMostViewController should return a VC that you should be able to send a message like presentViewController:animated:completion. It's purpose is to get you a VC that you can use to present a modal VC, so it will most likely stop and return at container classes like UINavigationController and NOT the VC contained within them. Should not be hard to adapt the code to do that too. I've tested this code in various situations in iOS 6, 7 and 8. Please let me know if you find bugs.

+ (UIViewController*) getTopMostViewController
{
    UIWindow *window = [[UIApplication sharedApplication] keyWindow];
    if (window.windowLevel != UIWindowLevelNormal) {
        NSArray *windows = [[UIApplication sharedApplication] windows];
        for(window in windows) {
            if (window.windowLevel == UIWindowLevelNormal) {
                break;
            }
        }
    }

    for (UIView *subView in [window subviews])
    {
        UIResponder *responder = [subView nextResponder];

        //added this block of code for iOS 8 which puts a UITransitionView in between the UIWindow and the UILayoutContainerView
        if ([responder isEqual:window])
        {
            //this is a UITransitionView
            if ([[subView subviews] count])
            {
                UIView *subSubView = [subView subviews][0]; //this should be the UILayoutContainerView
                responder = [subSubView nextResponder];
            }
        }

        if([responder isKindOfClass:[UIViewController class]]) {
            return [self topViewController: (UIViewController *) responder];
        }
    }

    return nil;
}

+ (UIViewController *) topViewController: (UIViewController *) controller
{
    BOOL isPresenting = NO;
    do {
        // this path is called only on iOS 6+, so -presentedViewController is fine here.
        UIViewController *presented = [controller presentedViewController];
        isPresenting = presented != nil;
        if(presented != nil) {
            controller = presented;
        }

    } while (isPresenting);

    return controller;
}

Answer 7

Way less code than all other solutions:

Objective-C version:

- (UIViewController *)getTopViewController {
    UIViewController *topViewController = [[[[UIApplication sharedApplication] delegate] window] rootViewController];
    while (topViewController.presentedViewController) topViewController = topViewController.presentedViewController;

    return topViewController;
}

Swift 2.0 version: (credit goes to Steve.B)

func getTopViewController() -> UIViewController {
    var topViewController = UIApplication.sharedApplication().delegate!.window!!.rootViewController!
    while (topViewController.presentedViewController != nil) {
        topViewController = topViewController.presentedViewController!
    }
    return topViewController
}

Works anywhere in your app, even with modals.

Answer 8

zirinisp's Answer in Swift:

extension UIWindow {

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

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

        if vc.isKindOfClass(UINavigationController.self) {

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

        } else if vc.isKindOfClass(UITabBarController.self) {

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

        } else {

            if let presentedViewController = vc.presentedViewController {

                return UIWindow.getVisibleViewControllerFrom(presentedViewController.presentedViewController!)

            } else {

                return vc;
            }
        }
    }
}

Usage:

 if let topController = window.visibleViewController() {
            println(topController)
        }

Answer 9

Specify title to each ViewController and then get the title of current ViewController by the code given below.

-(void)viewDidUnload {
  NSString *currentController = self.navigationController.visibleViewController.title;

Then check it by your title like this

  if([currentController isEqualToString:@"myViewControllerTitle"]){
    //write your code according to View controller.
  }
}

Answer 10

Mine is better! :)

extension UIApplication {
    var visibleViewController : UIViewController? {
        return keyWindow?.rootViewController?.topViewController
    }
}

extension UIViewController {
    fileprivate var topViewController: UIViewController {
        switch self {
        case is UINavigationController:
            return (self as! UINavigationController).visibleViewController?.topViewController ?? self
        case is UITabBarController:
            return (self as! UITabBarController).selectedViewController?.topViewController ?? self
        default:
            return presentedViewController?.topViewController ?? self
        }
    }
}

Answer 11

Why not just handle the push notification code in the app delegate? Is it directly related to a view?

You can check if a UIViewController's view is currently visible by checking if it's view's window property has a value. See more here.

Answer 12

Just addition to @zirinisp answer.

Create a file, name it UIWindowExtension.swift and paste the following snippet:

import UIKit

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

    public static func getVisibleViewControllerFrom(vc: UIViewController?) -> UIViewController? {
        if let nc = vc as? UINavigationController {
            return UIWindow.getVisibleViewControllerFrom(nc.visibleViewController)
        } else if let tc = vc as? UITabBarController {
            return UIWindow.getVisibleViewControllerFrom(tc.selectedViewController)
        } else {
            if let pvc = vc?.presentedViewController {
                return UIWindow.getVisibleViewControllerFrom(pvc)
            } else {
                return vc
            }
        }
    }
}

func getTopViewController() -> UIViewController? {
    let appDelegate = UIApplication.sharedApplication().delegate
    if let window = appDelegate!.window {
        return window?.visibleViewController
    }
    return nil
}

Use it anywhere as:

if let topVC = getTopViewController() {

}

Thanks to @zirinisp.

Answer 13

Regarding NSNotificationCenter Post above (sorry can't find out where to post a comment under it...)

In case some were getting the -[NSConcreteNotification allKeys] error of sorts. Change this:

-(void)didReceiveRemoteNotification:(NSDictionary *)userInfo

to this:

-(void)didReceiveRemoteNotification:(NSNotification*)notif {
NSDictionary *dict = notif.userInfo;
}

Answer 14

This worked for me. I have many targets that have different controllers so previous answers didn't seemed to work.

first you want this inside your AppDelegate class:

var window: UIWindow?

then, in your function

let navigationController = window?.rootViewController as? UINavigationController
if let activeController = navigationController!.visibleViewController {
    if activeController.isKindOfClass( MyViewController )  {
        println("I have found my controller!")    
   }
}

Answer 15

This is the best possible way that I have tried out. If it should help anyone...

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

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

    return topController;
}

Answer 16

extension UIApplication {
    /// The top most view controller
    static var topMostViewController: UIViewController? {
        return UIApplication.shared.keyWindow?.rootViewController?.visibleViewController
    }
}

extension UIViewController {
    /// The visible view controller from a given view controller
    var visibleViewController: UIViewController? {
        if let navigationController = self as? UINavigationController {
            return navigationController.topViewController?.visibleViewController
        } else if let tabBarController = self as? UITabBarController {
            return tabBarController.selectedViewController?.visibleViewController
        } else if let presentedViewController = presentedViewController {
            return presentedViewController.visibleViewController
        } else {
            return self
        }
    }
}

With this you can easily get the top post view controller like so

let viewController = UIApplication.topMostViewController

One thing to note is that if there's a UIAlertController currently being displayed, UIApplication.topMostViewController will return a UIAlertController.

Answer 17

Swift 2.0 version of jungledev's answer

func getTopViewController() -> UIViewController {
    var topViewController = UIApplication.sharedApplication().delegate!.window!!.rootViewController!
    while (topViewController.presentedViewController != nil) {
        topViewController = topViewController.presentedViewController!
    }
    return topViewController
}

Answer 18

I created a category for UIApplication with visibleViewControllers property. The main idea is pretty simple. I swizzled viewDidAppear and viewDidDisappear methods in UIViewController. In viewDidAppear method viewController is added to stack. In viewDidDisappear method viewController is removed from stack. NSPointerArray is used instead of NSArray to store weak UIViewController’s references . This approach works for any viewControllers hierarchy.

UIApplication+VisibleViewControllers.h

#import <UIKit/UIKit.h>

@interface UIApplication (VisibleViewControllers)

@property (nonatomic, readonly) NSArray<__kindof UIViewController *> *visibleViewControllers;

@end

UIApplication+VisibleViewControllers.m

#import "UIApplication+VisibleViewControllers.h"
#import <objc/runtime.h>

@interface UIApplication ()

@property (nonatomic, readonly) NSPointerArray *visibleViewControllersPointers;

@end

@implementation UIApplication (VisibleViewControllers)

- (NSArray<__kindof UIViewController *> *)visibleViewControllers {
    return self.visibleViewControllersPointers.allObjects;
}

- (NSPointerArray *)visibleViewControllersPointers {
    NSPointerArray *pointers = objc_getAssociatedObject(self, @selector(visibleViewControllersPointers));
    if (!pointers) {
        pointers = [NSPointerArray weakObjectsPointerArray];
        objc_setAssociatedObject(self, @selector(visibleViewControllersPointers), pointers, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    return pointers;
}

@end

@implementation UIViewController (UIApplication_VisibleViewControllers)

+ (void)swizzleMethodWithOriginalSelector:(SEL)originalSelector swizzledSelector:(SEL)swizzledSelector {
    Method originalMethod = class_getInstanceMethod(self, originalSelector);
    Method swizzledMethod = class_getInstanceMethod(self, swizzledSelector);
    BOOL didAddMethod = class_addMethod(self, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));
    if (didAddMethod) {
        class_replaceMethod(self, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
    } else {
        method_exchangeImplementations(originalMethod, swizzledMethod);
    }
}

+ (void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        [self swizzleMethodWithOriginalSelector:@selector(viewDidAppear:)
                               swizzledSelector:@selector(uiapplication_visibleviewcontrollers_viewDidAppear:)];
        [self swizzleMethodWithOriginalSelector:@selector(viewDidDisappear:)
                               swizzledSelector:@selector(uiapplication_visibleviewcontrollers_viewDidDisappear:)];
    });
}

- (void)uiapplication_visibleviewcontrollers_viewDidAppear:(BOOL)animated {
    [[UIApplication sharedApplication].visibleViewControllersPointers addPointer:(__bridge void * _Nullable)self];
    [self uiapplication_visibleviewcontrollers_viewDidAppear:animated];
}

- (void)uiapplication_visibleviewcontrollers_viewDidDisappear:(BOOL)animated {
    NSPointerArray *pointers = [UIApplication sharedApplication].visibleViewControllersPointers;
    for (int i = 0; i < pointers.count; i++) {
        UIViewController *viewController = [pointers pointerAtIndex:i];
        if ([viewController isEqual:self]) {
            [pointers removePointerAtIndex:i];
            break;
        }
    }
    [self uiapplication_visibleviewcontrollers_viewDidDisappear:animated];
}

@end

https://gist.github.com/medvedzzz/e6287b99011f2437ac0beb5a72a897f0

Swift 3 version

UIApplication+VisibleViewControllers.swift

import UIKit

extension UIApplication {

    private struct AssociatedObjectsKeys {
        static var visibleViewControllersPointers = "UIApplication_visibleViewControllersPointers"
    }

    fileprivate var visibleViewControllersPointers: NSPointerArray {
        var pointers = objc_getAssociatedObject(self, &AssociatedObjectsKeys.visibleViewControllersPointers) as! NSPointerArray?
        if (pointers == nil) {
            pointers = NSPointerArray.weakObjects()
            objc_setAssociatedObject(self, &AssociatedObjectsKeys.visibleViewControllersPointers, pointers, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
        return pointers!
    }

    var visibleViewControllers: [UIViewController] {
        return visibleViewControllersPointers.allObjects as! [UIViewController]
    }
}

extension UIViewController {

    private static func swizzleFunc(withOriginalSelector originalSelector: Selector, swizzledSelector: Selector) {
        let originalMethod = class_getInstanceMethod(self, originalSelector)
        let swizzledMethod = class_getInstanceMethod(self, swizzledSelector)
        let didAddMethod = class_addMethod(self, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))
        if didAddMethod {
            class_replaceMethod(self, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod))
        } else {
            method_exchangeImplementations(originalMethod, swizzledMethod);
        }
    }

    override open class func initialize() {
        if self != UIViewController.self {
            return
        }
        let swizzlingClosure: () = {
            UIViewController.swizzleFunc(withOriginalSelector: #selector(UIViewController.viewDidAppear(_:)),
                                         swizzledSelector: #selector(uiapplication_visibleviewcontrollers_viewDidAppear(_:)))
            UIViewController.swizzleFunc(withOriginalSelector: #selector(UIViewController.viewDidDisappear(_:)),
                                         swizzledSelector: #selector(uiapplication_visibleviewcontrollers_viewDidDisappear(_:)))
        }()
        swizzlingClosure
    }

    @objc private func uiapplication_visibleviewcontrollers_viewDidAppear(_ animated: Bool) {
        UIApplication.shared.visibleViewControllersPointers.addPointer(Unmanaged.passUnretained(self).toOpaque())
        uiapplication_visibleviewcontrollers_viewDidAppear(animated)
    }

    @objc private func uiapplication_visibleviewcontrollers_viewDidDisappear(_ animated: Bool) {
        let pointers = UIApplication.shared.visibleViewControllersPointers
        for i in 0..<pointers.count {
            if let pointer = pointers.pointer(at: i) {
                let viewController = Unmanaged<AnyObject>.fromOpaque(pointer).takeUnretainedValue() as? UIViewController
                if viewController.isEqual(self) {
                    pointers.removePointer(at: i)
                    break
                }
            }
        }
        uiapplication_visibleviewcontrollers_viewDidDisappear(animated)
    }
}

https://gist.github.com/medvedzzz/ee6f4071639d987793977dba04e11399

Answer 19

Always check your build configuration if you you are running your app with debug or release.

IMPORTANT NOTE: You can't be able to test it without running your app in debug mode

This was my solution