Trying to handle back navigation button action in iOS

Question

I need to detect when the user taps the  back  button on the navigation bar  in order to perform some operations when that occurs  I m trying to set manually an action to such button  this way    self navigationItem backBarButtonItem setAction  selector performBackNavigation      -  void performBackNavigation  id sender         Do operations      self navigationController popViewControllerAnimated NO       I firstly placed that code in the view controller itself  but I found that self navigationItem backBarButtonItem seemed to be nil  so I moved that same code to the parent view controller  which pushes the former to the navigation stack  But I m neither able to make it work  I ve read some posts regarding this issue  and some of them said that the selector needs to be set at the parent view controller  but for me it doesn t work anyway    What could I m doing wrong   Thanks

User · Answer

In Swift 4 or above   override func didMove toParent parent  UIViewController         if parent    nil              Back pressed

User · Answer

Perhaps this answers doesn t fit your explanation but question title  It s useful when you are trying to know when you tapped the back button on an UINavigationBar   In this case you can use UINavigationBarDelegate protocol and implement one of this methods   -  BOOL navigationBar  UINavigationBar   navigationBar shouldPopItem  UINavigationItem   item  -  void navigationBar  UINavigationBar   navigationBar didPopItem  UINavigationItem   item    When didPopItem method is called  it s because you either tapped the back button or you used  UINavigationBar popNavigationItemAnimated   method and the navigation bar did pop the item   Now  if you want to know what action triggered the didPopItem method you can use a flag   With this approach I don t need to manually add a left bar button item with an arrow image in order to make it similar to iOS back button  and be able to set my custom target action     Let s see an example   I have a view controller that has a page view controller  and a custom page indicator view  I m also using a custom UINavigationBar to display a title to know on what page am I and the back button to go back to the previous page  And I also can swipe to previous next page on page controller    pragma mark - UIPageViewController Delegate Methods -  void pageViewController  UIPageViewController   pageViewController didFinishAnimating  BOOL finished previousViewControllers  NSArray   previousViewControllers transitionCompleted  BOOL completed        if  completed                             if  currentIndex  gt  lastIndex                  UINavigationItem  navigationItem     UINavigationItem alloc  initWithTitle   Some page title                    someViewController navigationBar  pushNavigationItem navigationItem animated YES                  someViewController pageControl  setCurrentPage currentIndex             else                autoPop   YES    We pop the item automatically from code                 someViewController navigationBar  popNavigationItemAnimated YES                  someViewController pageControl  setCurrentPage currentIndex                        So then I implement UINavigationBar delegate methods    pragma mark - UINavigationBar Delegate Methods -  BOOL navigationBar  UINavigationBar   navigationBar shouldPopItem  UINavigationItem   item       if    autoPop               Pop by back button tap       else             Pop from code             autoPop   NO       return YES      In this case I used shouldPopItem because the pop is animated and I wanted to handle the back button immediately and not to wait until transition is finished

User · Answer

Set the UINavigationControllerDelegate and implement this delegate func  Swift    func navigationController navigationController  UINavigationController  willShowViewController viewController  UIViewController  animated  Bool        if viewController is  lt target class gt              if the only way to get back - back button was pressed

User · Answer

None of the other solutions worked for me  but this does   Create your own subclass of UINavigationController  make it implement the UINavigationBarDelegate  no need to manually set the navigation bar s delegate   add a UIViewController extension that defines a method to be called on a back button press  and then implement this method in your UINavigationController subclass   func navigationBar   navigationBar  UINavigationBar  shouldPop item  UINavigationItem  - gt  Bool       self topViewController  methodToBeCalledOnBackButtonPress       self popViewController animated  true      return true

User · Answer

The problem with didMoveToParentViewController it s that it gets called once the parent view is fully visible again so if you need to perform some tasks before that  it won t work   And it doesn t work with the driven animation gesture  Using willMoveToParentViewController works better   Objective-c  -  void willMoveToParentViewController  UIViewController   parent      if  parent    NULL                             Swift  override func willMoveToParentViewController parent  UIViewController         if parent    nil

User · Answer

Try this code using VIewWillDisappear method to detect the press of The back button of  NavigationItem   - void  viewWillDisappear  BOOL animated       if   self navigationController viewControllers indexOfObject self   NSNotFound                    Navigation button was pressed  Do some stuff           self navigationController popViewControllerAnimated NO              super viewWillDisappear animated       OR There is another way to get Action of the Navigation BAck button   Create Custom button for UINavigationItem of back button    For Ex       In ViewDidLoad     -  void viewDidLoad         super viewDidLoad       UIBarButtonItem  newBackButton     UIBarButtonItem alloc  initWithTitle   Home  style UIBarButtonItemStyleBordered target self action  selector home         self navigationItem leftBarButtonItem newBackButton     - void home  UIBarButtonItem   sender         self navigationController popToRootViewControllerAnimated YES       Swift    override func willMoveToParentViewController parent  UIViewController          if parent    nil                   Back btn Event handler

User · Answer

Use a custom UINavigationController subclass  which implements the shouldPop method    In Swift   class NavigationController  UINavigationController  UINavigationBarDelegate       var shouldPopHandler      - gt  Bool        func navigationBar   navigationBar  UINavigationBar  shouldPop item  UINavigationItem  - gt  Bool               if let shouldPopHandler   self shouldPopHandler   shouldPopHandler                         return false                   self popViewController animated  true     Needed          return true           When set  your shouldPopHandler   will be called to decide whether the controller will be pop or not  When not set it will just get popped as usual   It is a good idea to disable UINavigationControllers interactivePopGestureRecognizer as the gesture won t call your handler otherwise

User · Answer

Swift  override func didMoveToParentViewController parent  UIViewController         if parent    nil              Back pressed

User · Answer

This is Objective-C version of dadachi s Answer    Objective-C  -  void didMoveToParentViewController  UIViewController   parent      if  parent    NULL            NSLog   Back Pressed

User · Answer

Set the UINavigationBar s delegate  and then use   -  BOOL navigationBar  UINavigationBar   navigationBar shouldPopItem  UINavigationItem   item         handle the action here

[ios] Trying to handle "back" navigation button action in iOS

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