Leaking views when changing rootViewController inside transitionWithView

Question

While investigating a memory leak I discovered a problem related to the technique of calling setRootViewController: inside a transition animation block:

Answer 1

I came to this issue when using this code:

if var tc = self.transitionCoordinator() {

    var animation = tc.animateAlongsideTransitionInView((self.navigationController as VDLNavigationController).filtersVCContainerView, animation: { (context:UIViewControllerTransitionCoordinatorContext!) -> Void in
        var toVC = tc.viewControllerForKey(UITransitionContextToViewControllerKey) as BaseViewController
        (self.navigationController as VDLNavigationController).setFilterBarHiddenWithInteractivity(!toVC.filterable(), animated: true, interactive: true)
    }, completion: { (context:UIViewControllerTransitionCoordinatorContext!) -> Void in

    })
}

Disabling this code, fixed the problem. I managed to get this working by only enabling this transition animation when the filterbar which gets animated is initialised.

It's not really the answer you're looking for, but it could bring you on the right pad for finding your solution.

Answer 2

I had a similar issue recently. I had to manually remove that UITransitionView from the window to fix the problem, then call dismiss on the previous root view controller to ensure its deallocated.

The fix is not really very nice but unless you've found a better way since posting the question, its the only thing I've found to work! viewController is just the newController from your original question.

UIViewController *previousRootViewController = self.window.rootViewController;

self.window.rootViewController = viewController;

// Nasty hack to fix http://stackoverflow.com/questions/26763020/leaking-views-when-changing-rootviewcontroller-inside-transitionwithview
// The presenting view controllers view doesn't get removed from the window as its currently transistioning and presenting a view controller
for (UIView *subview in self.window.subviews) {
    if ([subview isKindOfClass:NSClassFromString(@"UITransitionView")]) {
        [subview removeFromSuperview];
    }
}
// Allow the view controller to be deallocated
[previousRootViewController dismissViewControllerAnimated:NO completion:^{
    // Remove the root view in case its still showing
    [previousRootViewController.view removeFromSuperview];
}];

I hope this helps you fix your problem too, it's an absolute pain in the arse!

Swift 3.0

(See edit history for other Swift versions)

For a nicer implementation as a extension on UIWindow allowing an optional transition to be passed in.

extension UIWindow {

    /// Fix for http://stackoverflow.com/a/27153956/849645
    func set(rootViewController newRootViewController: UIViewController, withTransition transition: CATransition? = nil) {

        let previousViewController = rootViewController

        if let transition = transition {
            // Add the transition
            layer.add(transition, forKey: kCATransition)
        }

        rootViewController = newRootViewController

        // Update status bar appearance using the new view controllers appearance - animate if needed
        if UIView.areAnimationsEnabled {
            UIView.animate(withDuration: CATransaction.animationDuration()) {
                newRootViewController.setNeedsStatusBarAppearanceUpdate()
            }
        } else {
            newRootViewController.setNeedsStatusBarAppearanceUpdate()
        }

        if #available(iOS 13.0, *) {
            // In iOS 13 we don't want to remove the transition view as it'll create a blank screen
        } else {
            // The presenting view controllers view doesn't get removed from the window as its currently transistioning and presenting a view controller
            if let transitionViewClass = NSClassFromString("UITransitionView") {
                for subview in subviews where subview.isKind(of: transitionViewClass) {
                    subview.removeFromSuperview()
                }
            }
        }
        if let previousViewController = previousViewController {
            // Allow the view controller to be deallocated
            previousViewController.dismiss(animated: false) {
                // Remove the root view in case its still showing
                previousViewController.view.removeFromSuperview()
            }
        }
    }
}

Usage:

window.set(rootViewController: viewController)

Or

let transition = CATransition()
transition.type = kCATransitionFade
window.set(rootViewController: viewController, withTransition: transition)

Answer 3

Had a similar issue. In my case I had a viewController hierarchy, and one of the child view controllers had a presented view controller. When I changed then the windows root view controller, for some reason, the presented view controller was still in the memory. So, the solution was to dismiss all view controllers before I change the windows root view controller.

Answer 4

I faced this issue and it annoyed me for a whole day. I've tried @Rich's obj-c solution and it turns out when I want to present another viewController after that, I will be blocked with a blank UITransitionView.

Finally, I figured out this way and it worked for me.

- (void)setRootViewController:(UIViewController *)rootViewController {
    // dismiss presented view controllers before switch rootViewController to avoid messed up view hierarchy, or even crash
    UIViewController *presentedViewController = [self findPresentedViewControllerStartingFrom:self.window.rootViewController];
    [self dismissPresentedViewController:presentedViewController completionBlock:^{
        [self.window setRootViewController:rootViewController];
    }];
}

- (void)dismissPresentedViewController:(UIViewController *)vc completionBlock:(void(^)())completionBlock {
    // if vc is presented by other view controller, dismiss it.
    if ([vc presentingViewController]) {
        __block UIViewController* nextVC = vc.presentingViewController;
        [vc dismissViewControllerAnimated:NO completion:^ {
            // if the view controller which is presenting vc is also presented by other view controller, dismiss it
            if ([nextVC presentingViewController]) {
                [self dismissPresentedViewController:nextVC completionBlock:completionBlock];
            } else {
                if (completionBlock != nil) {
                    completionBlock();
                }
            }
        }];
    } else {
        if (completionBlock != nil) {
            completionBlock();
        }
    }
}

+ (UIViewController *)findPresentedViewControllerStartingFrom:(UIViewController *)start {
    if ([start isKindOfClass:[UINavigationController class]]) {
        return [self findPresentedViewControllerStartingFrom:[(UINavigationController *)start topViewController]];
    }

    if ([start isKindOfClass:[UITabBarController class]]) {
        return [self findPresentedViewControllerStartingFrom:[(UITabBarController *)start selectedViewController]];
    }

    if (start.presentedViewController == nil || start.presentedViewController.isBeingDismissed) {
        return start;
    }

    return [self findPresentedViewControllerStartingFrom:start.presentedViewController];
}

Alright, now all you have to do is call [self setRootViewController:newViewController]; when you want to switch root view controller.

Answer 5

I try a simple thing which work for me on iOs 9.3 : just remove the old viewController's view from its hierarchy during dismissViewControllerAnimated completion.

Let's work on X, Y, and Z view as explained by benzado :

That is, this sequence of operations...

1. X becomes Root View Controller
2. X presents Y, so that Y's view is on screen
3. Using transitionWithView: to make Z the new Root View Controller

Which give :

////
//Start point :

let X = UIViewController ()
let Y = UIViewController ()
let Z = UIViewController ()

window.rootViewController = X
X.presentViewController (Y, animated:true, completion: nil)

////
//Transition :

UIView.transitionWithView(window,
                          duration: 0.25,
                          options: UIViewAnimationOptions.TransitionFlipFromRight,
                          animations: { () -> Void in
                                X.dismissViewControllerAnimated(false, completion: {
                                        X.view.removeFromSuperview()
                                    })
                                window.rootViewController = Z
                           },
                           completion: nil)

In my case, X and Y are well dealloc and their's view are no more in hierarchy !