iPhone viewWillAppear not firing

Question

I ve read numerous posts about people having problems with viewWillAppear when you do not create your view hierarchy just right  My problem is I can t figure out what that means   If I create a RootViewController and call addSubView on that controller  I would expect the added view s  to be wired up for viewWillAppear events    Does anyone have an example of a complex programmatic view hierarchy that successfully receives viewWillAppear events at every level   Apple s Docs state      Warning  If the view belonging to a view controller is added to a view hierarchy directly  the view controller will not receive this message  If you insert or add a view to the view hierarchy  and it has a view controller  you should send the associated view controller this message directly  Failing to send the view controller this message will prevent any associated animation from being displayed    The problem is that they don t describe how to do this  What does  directly  mean  How do you  indirectly  add a view   I am fairly new to Cocoa and iPhone so it would be nice if there were useful examples from Apple besides the basic Hello World crap

User · Answer

ViewWillAppear is an override method of UIViewController class so adding a subView will not call viewWillAppear  but when you present  push   pop  show   setFront Or popToRootViewController from a viewController then  viewWillAppear for presented viewController will get called

User · Answer

A very common mistake is as follows  You have one view  UIView  a  and another one  UIView  b  You add b to a as a subview  If you try to call viewWillAppear in b  it will never be fired  because it is a subview of a

User · Answer

Correct way to do this is using UIViewController containment api    -  void viewDidLoad         super viewDidLoad           Do any additional setup after loading the view       UIViewController  viewController              self addChildViewController viewController         self view addSubview viewController view         viewController didMoveToParentViewController self

User · Answer

I use this code for push and pop view controllers   push     self navigationController pushViewController detaiViewController animated YES    detailNewsViewController viewWillAppear YES     pop     self navigationController popViewControllerAnimated YES  viewWillAppear YES        and it works fine for me

User · Answer

I think that adding a subview doesn t necessarily mean that the view will appear  so there is not an automatic call to the class s method that it will

User · Answer

I finally found a solution for this THAT WORKS   UINavigationControllerDelegate  I think the gist of it is to set your nav control s delegate to the viewcontroller it is in  and implement UINavigationControllerDelegate and it s two methods  Brilliant  I m so excited i finally found a solution

User · Answer

I m not sure this is the same problem that I solved  In some occasions  method doesn t executed with normal way such as   self methodOne     Try  -  void viewWillAppear  BOOL animated        self performSelector  selector methodOne              withObject nil afterDelay 0

User · Answer

I have created a class that solves this problem   Just set it as a delegate of your navigation controller  and implement simple one or two methods in your view controller - that will get called when the view is about to be shown or has been shown via NavigationController  Here s the GIST showing the code

User · Answer

I m not 100  sure on this  but I think that adding a view to the view hierarchy directly means calling -addSubview  on the view controller s view  e g    viewController view addSubview anotherViewController view   instead of pushing a new view controller onto the navigation controller s stack

User · Answer

In my case problem was with custom transition animation  When set modalPresentationStyle    custom viewWillAppear not called  in custom transition animation class need call methods  beginAppearanceTransition and endAppearanceTransition

User · Answer

My issue was that viewWillAppear was not called when unwinding from a segue  The answer was to put a call to viewWillAppear true  in the unwind segue in the View Controller that you segueing back to   IBAction   func unwind for unwindSegue  UIStoryboardSegue  ViewController subsequentVC  Any        viewWillAppear true

User · Answer

self navigationController setDelegate self     Set the delegate to the root view controller

User · Answer

If you use a navigation controller and set its delegate  then the view Will Did  Appear Disappear  methods are not invoked   You need to use the navigation controller delegate methods instead   navigationController willShowViewController animated  navigationController didShowViewController animated

User · Answer

I just had this problem myself and it took me 3 full hours  2 of which googling  to fix it   What turned out to help was to simply delete the app from the device simulator  clean and then run again   Hope that helps

User · Answer

Views are added  directly  by calling  view addSubview subview   Views are added  indirectly  by methods such as tab bars or nav bars that swap subviews   Any time you call  view addSubview subviewController view   you should then call  subviewController viewWillAppear NO   or YES as your case may be    I had this problem when I implemented my own custom root-view management system for a subscreen in a game  Manually adding the call to viewWillAppear cured my problem

User · Answer

Thanks iOS 13       ViewWillDisappear  ViewDidDisappear  ViewWillAppear and   ViewDidAppear won t get called on a presenting view controller on   iOS 13 which uses a new modal presentation that doesn t cover the   whole screen    Credits are going to Arek Holko  He really saved my day

User · Answer

I ve been using a navigation controller  When I want to either descend to another level of data or show my custom view I use the following    self navigationController pushViewController  lt view gt  animated  lt BOOL gt      When I do this  I do get the viewWillAppear function to fire  I suppose this qualifies as  indirect  because I m not calling the actual addSubView method myself  I don t know if this is 100  applicable to your application since I can t tell if you re using a navigation controller  but maybe it will provide a clue

User · Answer

I ve run into this same problem  Just send a viewWillAppear message to your view controller before you add it as a subview   There is one BOOL parameter which tells the view controller if it s being animated to appear or not     myViewController viewWillAppear NO     Look at RootViewController m in the Metronome example     I actually found Apple s example projects great  There s a LOT more than HelloWorld

User · Answer

iOS 13 bit my app in the butt here  If you ve noticed behavior change as of iOS 13 just set the following before you push it   yourVC modalPresentationStyle   UIModalPresentationFullScreen    You may also need to set it in your  storyboard in the Attributes inspector  set Presentation to Full Screen    This will make your app behave as it did in prior versions of iOS

User · Answer

For Swift  First create the protocol to call what you wanted to call in viewWillAppear  protocol MyViewWillAppearProtocol func myViewWillAppear      Second  create the class  class ForceUpdateOnViewAppear  NSObject  UINavigationControllerDelegate   func navigationController   navigationController  UINavigationController  willShow viewController  UIViewController  animated  Bool       if let updatedCntllr  MyViewWillAppearProtocol   viewController as  MyViewWillAppearProtocol          updatedCntllr myViewWillAppear                Third  make the instance of ForceUpdateOnViewAppear to be the member of the appropriate class that have the access to the Navigation Controller and exists as long as Navigation controller exists  It may be for example the root view controller of the navigation controller or the class that creates or present it  Then assign the instance of  ForceUpdateOnViewAppear to the Navigation Controller delegate property as early as possible

User · Answer

As no answer is accepted and people  like I did  land here I give my variation  Though I am not sure that was the original problem  When the navigation controller is added as a subview to a another view you must call the viewWillAppear Dissappear etc  methods yourself like this   -  void  viewWillAppear  BOOL animated        super viewWillAppear animated         subNavCntlr viewWillAppear animated      -  void  viewWillDisappear  BOOL animated        super viewWillDisappear animated         subNavCntlr viewWillDisappear animated       Just to make the example complete  This code appears in my ViewController where I created and added the the navigation controller into a view that I placed on the view    -  void viewDidLoad           This is the root View Controller     rootTable  rootTableController     rootTable alloc                   initWithStyle UITableViewStyleGrouped        subNavCntlr     UINavigationController alloc                       initWithRootViewController rootTableController         rootTableController release        subNavCntlr view frame   subNavContainer bounds        subNavContainer addSubview subNavCntlr view         super viewDidLoad       the  h looks like this   interface navTestViewController   UIViewController  lt UINavigationControllerDelegate gt        IBOutlet UIView  subNavContainer      UINavigationController  subNavCntlr      end   In the nib file I have the view and below this view I have a label a image and the container  another view  where i put the controller in  Here is how it looks  I had to scramble some things as this was work for a client

User · Answer

I think what they mean  directly  is by hooking things up just the same way as the xcode  Navigation Application  template does  which sets the UINavigationController as the sole subview of the application s UIWindow   Using that template is the only way I ve been able to get the Will Did Appear Disappear methods called on the object ViewControllers upon push pops of those controllers in the UINavigationController   None of the other solutions in the answers here worked for me  including implementing them in the RootController and passing them through to the  child  NavigationController    Those functions  will did appear disappear  were only called in my RootController upon showing hiding the top-level VCs  my  login  and navigationVCs  not the sub-VCs in the navigation controller  so I had no opportunity to  pass them through  to the  Nav VC   I ended up using the UINavigationController s delegate functionality to look for the particular transitions that required follow-up functionality in my app  and that works  but it requires a bit more work in order to get both the disappear and appear functionality  simulated    Also it s a matter of principle to get it to work after banging my head against this problem for hours today    Any working code snippets using a custom RootController and a child navigation VC would be much appreciated

User · Answer

In my case that was just a weird bug on the ios 12 1 emulator  Disappeared after launching on real device

User · Answer

If you use a navigation controller and set its delegate  then the view Will Did  Appear Disappear  methods are not invoked   You need to use the navigation controller delegate methods instead   navigationController willShowViewController animated  navigationController didShowViewController animated

User · Answer

I m not 100  sure on this  but I think that adding a view to the view hierarchy directly means calling -addSubview  on the view controller s view  e g    viewController view addSubview anotherViewController view   instead of pushing a new view controller onto the navigation controller s stack

User · Answer

You should only have 1 UIViewController active at any time  Any subviews you want to manipulate should be exactly that - subVIEWS - i e  UIView   I use a simlple technique for managing my view hierarchy and have yet to run into a problem since I started doing things this way   There are 2 key points    a single UIViewController should be used to manage  a screen s worth  of your app use UINavigationController for changing views   What do I mean by  a screen s worth    It s a bit vague on purpose  but generally it s a feature or section of your app   If you ve got a few screens with the same background image but different overlays popups etc   that should be 1 view controller and several child views   You should never find yourself working with 2 view controllers   Note you can still instantiate a UIView in one view controller and add it as a subview of another view controller if you want certain areas of the screen to be shown in multiple view controllers   As for UINavigationController - this is your best friend   Turn off the navigation bar and specify NO for animated  and you have an excellent way of switching screens on demand   You can push and pop view controllers if they re in a hierarchy  or you can prepare an array of view controllers  including an array containing a single VC  and set it to be the view stack using setViewControllers   This gives you total freedom to change VC s  while gaining all the advantages of working within Apple s expected model and getting all events etc  fired properly   Here s what I do every time when I start an app    start from a window-based app add a UINavigationController as the window s rootViewController add whatever I want my first UIViewController to be as the rootViewController of the nav controller    note starting from window-based is just a personal preference - I like to construct things myself so I know exactly how they are built  It should work fine with view-based template   All events fire correctly and basically life is good   You can then spend all your time writing the important bits of your app and not messing about trying to manually hack view hierarchies into shape

User · Answer

Firstly  the tab bar should be at the root level  ie  added to the window  as stated in the Apple documentation   This is key for correct behavior   Secondly  you can use UITabBarDelegate   UINavigationBarDelegate to forward the notifications on manually  but I found that to get the whole hierarchy of view calls to work correctly  all I had to do was manually call    tabBarController viewWillAppear NO    tabBarController viewDidAppear NO     and   navBarController viewWillAppear NO    navBarController viewDidAppear NO        just ONCE before setting up the view controllers on the respective controller  right after allocation   From then on  it correctly called these methods on its child view controllers   My hierarchy is like this   window     UITabBarController  subclass of          UIViewController  subclass of      lt -- manually calls  navController viewWill DidAppear             UINavigationController  subclass of                  UIViewController  subclass of      lt -- still receives viewWill Did  etc all the way down from a tab switch at the top of the chain without needing to use ANY delegate methods   Just calling the mentioned methods on the tab nav controller the first time ensured that ALL the events were forwarded correctly   It stopped me needing to call them manually from the UINavigationBarDelegate   UITabBarControllerDelegate methods   Sidenote  Curiously  when it didn t work  the private method   -  void transitionFromViewController  UIViewController  aFromViewController toViewController  UIViewController  aToViewController       which you can see from the callstack on a working implementation  usually calls the viewWill Did   methods but didn t until I performed the above  even though it was called    I think it is VERY important that the UITabBarController is at window level though and the documents seem to back this up   Hope that was clear ish   happy to answer further questions

User · Answer

I just had the same issue  In my application I have 2 navigation controllers and pushing the same view controller in each of them worked in one case and not in the other  I mean that when pushing the exact same view controller in the first UINavigationController  viewWillAppear was called but not when pushed in the second navigation controller   Then I came across this post UINavigationController should call viewWillAppear viewWillDisappear methods   And realized that my second navigation controller did redefine viewWillAppear  Screening the code showed that I was not calling    super viewWillAppear animated     I added it and it worked    The documentation says      If you override this method  you must call super at some point in your implementation

User · Answer

In case this helps anyone  I had a similar problem where my ViewWillAppear is not firing on a UITableViewController  After a lot of playing around  I realized that the problem was that the UINavigationController that is controlling my UITableView is not on the root view  Once I fix that  it is now working like a champ

[iphone] iPhone viewWillAppear not firing

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