I'm trying to build a menu with 4 different levels, where each level represents a UIViewController. I want the menu and each of its levels to be presented modally. Currently, I'm doing this by letting a base ViewController (VC) present another, which in turn presents a 3rd which presents a 4th (the structure would be A-B-C-D where each - represents a call to UIViewController.present(_:animated:completion:) for the respective level).
I'm then implementing the UIViewControllerTransitioningDelegate and supplying it with a custom transition object. This works well for the first 3 levels (ie. the menu works as expected for level A-B-C), but when I'm on the 4th level and trying to dismiss it (ie. going from A-B-C-D to A-B-C ), the B level is briefly showing instead of the C level while the dismissal-animation is playing. After the animation is done, level C pops up over B again.
I suspect the problem lies in presenting more than 3 VC:s in a hierarchy somehow, but this does not occur when using the default dismissal animation instead of the custom one I'm using.
Maybe I should go for a different navigation approach, or is there some way to circumvent this behavior? I do need the menu to be "modal-style" which from what I can tell would prevent me from using a UINavigationController (I don't want the navigation bars).
Help is highly appreciated.
--- EDIT ---
Here is a "pseudo code" example of what I'm trying to accomplish, as the project is quite big and I'd have trouble pasting it all:
class A: UIViewController: UIViewControllerTransitioningDelegate {
func viewDidLoad(){...}
.
.
.
#objc func presentB(){
self.present(B, animated: true, completion: nil)
}
func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
return CustomTransition(presenting: true)
}
func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
return CustomTransition(presenting: false)
}
}
class B: UIViewController: UIViewControllerTransitioningDelegate {
func viewDidLoad(){...}
.
.
.
#objc func dismiss(){
self.dismiss(animated: true, completion: nil)
}
#objc func presentC(){
self.present(C, animated: true, completion: nil)
}
func animationController(forPresented:presenting:source:) -> UIViewControllerAnimatedTransitioning? { ... }
func animationController(forDismissed:) -> UIViewControllerAnimatedTransitioning? {...}
}
class C: UIViewController: UIViewControllerTransitioningDelegate {
func viewDidLoad(){...}
.
.
.
#objc func dismiss(){
self.dismiss(animated: true, completion: nil)
}
#objc func presentD(){
self.present(D, animated: true, completion: nil)
}
func animationController(forPresented:presenting:source:) -> UIViewControllerAnimatedTransitioning? { ... }
func animationController(forDismissed:) -> UIViewControllerAnimatedTransitioning? {...}
}
class D: UIViewController {
func viewDidLoad(){...}
.
.
.
#objc func dismiss(){
self.dismiss(animated: true, completion: nil)
}
}
When dismissing a modal view controller using dismissViewController, there is the option to provide a completion block. Is there a similar equivalent for popViewController?
The completion argument is quite handy. For instance, I can use it to hold off removing a row from a tableview until the modal is off screen, letting the user see the row animation. When returning from a pushed view controller, I would like the same opportunity.
I have tried placing popViewController in an UIView animation block, where I do have access to a completion block. However, this produces some unwanted side effects on the view being popped to.
If there is no such method available, what are some workarounds?
I know an answer has been accepted over two years ago, however this answer is incomplete.
There is no way to do what you're wanting out-of-the-box
This is technically correct because the UINavigationController API doesn't offer any options for this. However by using the CoreAnimation framework it's possible to add a completion block to the underlying animation:
[CATransaction begin];
[CATransaction setCompletionBlock:^{
// handle completion here
}];
[self.navigationController popViewControllerAnimated:YES];
[CATransaction commit];
The completion block will be called as soon as the animation used by popViewControllerAnimated: ends. This functionality has been available since iOS 4.
Swift 5 version - works like a charm. Based on this answer
extension UINavigationController {
func pushViewController(viewController: UIViewController, animated: Bool, completion: #escaping () -> Void) {
pushViewController(viewController, animated: animated)
if animated, let coordinator = transitionCoordinator {
coordinator.animate(alongsideTransition: nil) { _ in
completion()
}
} else {
completion()
}
}
func popViewController(animated: Bool, completion: #escaping () -> Void) {
popViewController(animated: animated)
if animated, let coordinator = transitionCoordinator {
coordinator.animate(alongsideTransition: nil) { _ in
completion()
}
} else {
completion()
}
}
}
I made a Swift version with extensions with #JorisKluivers answer.
This will call a completion closure after the animation is done for both push and pop.
extension UINavigationController {
func popViewControllerWithHandler(completion: ()->()) {
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
self.popViewControllerAnimated(true)
CATransaction.commit()
}
func pushViewController(viewController: UIViewController, completion: ()->()) {
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
self.pushViewController(viewController, animated: true)
CATransaction.commit()
}
}
SWIFT 4.1
extension UINavigationController {
func pushToViewController(_ viewController: UIViewController, animated:Bool = true, completion: #escaping ()->()) {
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
self.pushViewController(viewController, animated: animated)
CATransaction.commit()
}
func popViewController(animated:Bool = true, completion: #escaping ()->()) {
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
self.popViewController(animated: animated)
CATransaction.commit()
}
func popToViewController(_ viewController: UIViewController, animated:Bool = true, completion: #escaping ()->()) {
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
self.popToViewController(viewController, animated: animated)
CATransaction.commit()
}
func popToRootViewController(animated:Bool = true, completion: #escaping ()->()) {
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
self.popToRootViewController(animated: animated)
CATransaction.commit()
}
}
Working with or without animation properly, and also includes popToRootViewController:
// updated for Swift 3.0
extension UINavigationController {
private func doAfterAnimatingTransition(animated: Bool, completion: #escaping (() -> Void)) {
if let coordinator = transitionCoordinator, animated {
coordinator.animate(alongsideTransition: nil, completion: { _ in
completion()
})
} else {
DispatchQueue.main.async {
completion()
}
}
}
func pushViewController(viewController: UIViewController, animated: Bool, completion: #escaping (() -> Void)) {
pushViewController(viewController, animated: animated)
doAfterAnimatingTransition(animated: animated, completion: completion)
}
func popViewController(animated: Bool, completion: #escaping (() -> Void)) {
popViewController(animated: animated)
doAfterAnimatingTransition(animated: animated, completion: completion)
}
func popToRootViewController(animated: Bool, completion: #escaping (() -> Void)) {
popToRootViewController(animated: animated)
doAfterAnimatingTransition(animated: animated, completion: completion)
}
}
I had the same issue. And because I had to use it in multiple occasions, and within chains of completion blocks, I created this generic solution in an UINavigationController subclass:
- (void) navigationController:(UINavigationController *) navigationController didShowViewController:(UIViewController *) viewController animated:(BOOL) animated {
if (_completion) {
dispatch_async(dispatch_get_main_queue(),
^{
_completion();
_completion = nil;
});
}
}
- (UIViewController *) popViewControllerAnimated:(BOOL) animated completion:(void (^)()) completion {
_completion = completion;
return [super popViewControllerAnimated:animated];
}
Assuming
#interface NavigationController : UINavigationController <UINavigationControllerDelegate>
and
#implementation NavigationController {
void (^_completion)();
}
and
- (id) initWithRootViewController:(UIViewController *) rootViewController {
self = [super initWithRootViewController:rootViewController];
if (self) {
self.delegate = self;
}
return self;
}
Based on #HotJard's answer, when all you want is just a couple of lines of code. Quick and Easy.
Swift 4:
_ = self.navigationController?.popViewController(animated: true)
self.navigationController?.transitionCoordinator.animate(alongsideTransition: nil) { _ in
doWhatIWantAfterContollerHasPopped()
}
There is no way to do what you're wanting out-of-the-box. i.e. there is no method with a completion block for popping a view controller from a nav stack.
What I would do is put the logic in viewDidAppear. That will be called when the view has finished coming on screen. It'll be called for all different scenarios of the view controller appearing, but that should be fine.
Or you could use the UINavigationControllerDelegate method navigationController:didShowViewController:animated: to do a similar thing. This is called when the navigation controller has finished pushing or popping a view controller.
For 2018 ...
if you have this ...
navigationController?.popViewController(animated: false)
// I want this to happen next, help! ->
nextStep()
and you want to add a completion ...
CATransaction.begin()
navigationController?.popViewController(animated: true)
CATransaction.setCompletionBlock({ [weak self] in
self?.nextStep() })
CATransaction.commit()
it's that simple.
Handy tip...
It's the same deal for the handy popToViewController call.
A typical thing is you have an onboarding stack of a zillion screens. When finally done, you go all the way back to your "base" screen, and then finally fire up the app.
So in the "base" screen, to go "all the way back", popToViewController(self
func onboardingStackFinallyComplete() {
CATransaction.begin()
navigationController?.popToViewController(self, animated: false)
CATransaction.setCompletionBlock({ [weak self] in
guard let self = self else { return }
.. actually launch the main part of the app
})
CATransaction.commit()
}
Cleaned up Swift 4 version based on this answer.
extension UINavigationController {
func pushViewController(_ viewController: UIViewController, animated: Bool, completion: #escaping () -> Void) {
self.pushViewController(viewController, animated: animated)
self.callCompletion(animated: animated, completion: completion)
}
func popViewController(animated: Bool, completion: #escaping () -> Void) -> UIViewController? {
let viewController = self.popViewController(animated: animated)
self.callCompletion(animated: animated, completion: completion)
return viewController
}
private func callCompletion(animated: Bool, completion: #escaping () -> Void) {
if animated, let coordinator = self.transitionCoordinator {
coordinator.animate(alongsideTransition: nil) { _ in
completion()
}
} else {
completion()
}
}
}
The completion block is called after the viewDidDisappear method is called on the presented view controller, So putting code in the viewDidDisappear method of the popped view controller should work the same as a completion block.
Swift 3 answer, thanks to this answer: https://stackoverflow.com/a/28232570/3412567
//MARK:UINavigationController Extension
extension UINavigationController {
//Same function as "popViewController", but allow us to know when this function ends
func popViewControllerWithHandler(completion: #escaping ()->()) {
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
self.popViewController(animated: true)
CATransaction.commit()
}
func pushViewController(viewController: UIViewController, completion: #escaping ()->()) {
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
self.pushViewController(viewController, animated: true)
CATransaction.commit()
}
}
Swift 4 version with optional viewController parameter to pop to a specific one.
extension UINavigationController {
func pushViewController(viewController: UIViewController, animated:
Bool, completion: #escaping () -> ()) {
pushViewController(viewController, animated: animated)
if let coordinator = transitionCoordinator, animated {
coordinator.animate(alongsideTransition: nil) { _ in
completion()
}
} else {
completion()
}
}
func popViewController(viewController: UIViewController? = nil,
animated: Bool, completion: #escaping () -> ()) {
if let viewController = viewController {
popToViewController(viewController, animated: animated)
} else {
popViewController(animated: animated)
}
if let coordinator = transitionCoordinator, animated {
coordinator.animate(alongsideTransition: nil) { _ in
completion()
}
} else {
completion()
}
}
}
Please refer to recent version(5.1) of Swifty & SDK-like way,
extension UINavigationController {
func popViewController(animated: Bool, completion: (() -> ())? = nil) {
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
popViewController(animated: animated)
CATransaction.commit()
}
func pushViewController(_ viewController: UIViewController, animated: Bool, completion: (() -> ())? = nil) {
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
pushViewController(viewController, animated: animated)
CATransaction.commit()
}
}
2020 Swift 5.1 way
This solution guarantee that completion is executed after popViewController is fully finished. You can test it by doing another operation on the NavigationController in completion: In all other solutions above the UINavigationController is still busy with popViewController operation and does not respond.
public class NavigationController: UINavigationController, UINavigationControllerDelegate
{
private var completion: (() -> Void)?
override init(rootViewController: UIViewController) {
super.init(rootViewController: rootViewController)
delegate = self
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
public override func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool)
{
if self.completion != nil {
DispatchQueue.main.async(execute: {
self.completion?()
self.completion = nil
})
}
}
func popViewController(animated: Bool, completion: #escaping () -> Void) -> UIViewController?
{
self.completion = completion
return super.popViewController(animated: animated)
}
}
Just for completeness, I've made an Objective-C category ready to use:
// UINavigationController+CompletionBlock.h
#import <UIKit/UIKit.h>
#interface UINavigationController (CompletionBlock)
- (UIViewController *)popViewControllerAnimated:(BOOL)animated completion:(void (^)()) completion;
#end
// UINavigationController+CompletionBlock.m
#import "UINavigationController+CompletionBlock.h"
#implementation UINavigationController (CompletionBlock)
- (UIViewController *)popViewControllerAnimated:(BOOL)animated completion:(void (^)()) completion {
[CATransaction begin];
[CATransaction setCompletionBlock:^{
completion();
}];
UIViewController *vc = [self popViewControllerAnimated:animated];
[CATransaction commit];
return vc;
}
#end
There is a pod called UINavigationControllerWithCompletionBlock which adds support for a completion block when both pushing and popping on a UINavigationController.
Use the next extension on your code: (Swift 4)
import UIKit
extension UINavigationController {
func popViewController(animated: Bool = true, completion: #escaping () -> Void) {
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
popViewController(animated: animated)
CATransaction.commit()
}
func pushViewController(_ viewController: UIViewController, animated: Bool = true, completion: #escaping () -> Void) {
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
pushViewController(viewController, animated: animated)
CATransaction.commit()
}
}
I achieved exactly this with precision using a block. I wanted my fetched results controller to show the row that was added by the modal view, only once it had fully left the screen, so the user could see the change happening. In prepare for segue which is responsible for showing the modal view controller, I set the block I want to execute when the modal disappears. And in the modal view controller I override viewDidDissapear and then call the block. I simply begin updates when the modal is going to appear and end updates when it disappears, but that is because I'm using a NSFetchedResultsController however you can do whatever you like inside the block.
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
if([segue.identifier isEqualToString:#"addPassword"]){
UINavigationController* nav = (UINavigationController*)segue.destinationViewController;
AddPasswordViewController* v = (AddPasswordViewController*)nav.topViewController;
...
// makes row appear after modal is away.
[self.tableView beginUpdates];
[v setViewDidDissapear:^(BOOL animated) {
[self.tableView endUpdates];
}];
}
}
#interface AddPasswordViewController : UITableViewController<UITextFieldDelegate>
...
#property (nonatomic, copy, nullable) void (^viewDidDissapear)(BOOL animated);
#end
#implementation AddPasswordViewController{
...
-(void)viewDidDisappear:(BOOL)animated{
[super viewDidDisappear:animated];
if(self.viewDidDissapear){
self.viewDidDissapear(animated);
}
}
#end
I found that the implementation of func navigationController(UINavigationController, didShow: UIViewController, animated: Bool) is the only working solution here.
We may make it better using RxSwift:
import UIKit
import RxSwift
import RxCocoa
extension Reactive where Base: UINavigationController {
func popToViewController(_ viewController: UIViewController, animated: Bool) -> ControlEvent<ShowEvent> {
let source = didShow
.filter { [weak viewController] event in
viewController == event.0
}
.take(1)
_ = base.popToViewController(viewController, animated: animated)
return ControlEvent(events: source)
}
}
Usage:
// let navigationController = UINavigationController(rootViewController: page1)
// navigationController.pushViewController(page2, animated: false)
navigationController.rx
.popToViewController(page1, animated: true)
.bind { _ in
// pop completion
}
.disposed(by: disposeBag)
I think viewDidDisappear(_ animated: Bool) function can help for this. It will be called when the view did disappeared completely.
override func viewDidDisappear(_ animated: Bool) {
super.viewDidDisappear(animated)
//do the stuff here
}