How to tell if UIViewController s view is visible

Question

I have a tab bar application  with many views  Is there a way to know if a particular UIViewController is currently visible from within the UIViewController    looking for a property

User · Answer

XCode 6 4  for iOS 8 4  ARC enabled  Obviously lots of ways of doing it   The one that has worked for me is the following      property nonatomic  readonly  getter isKeyWindow  BOOL keyWindow   This can be used in any view controller in the following way    self view window isKeyWindow    If you call this property in - void viewDidLoad you get 0  then if you call this after - void viewDidAppear  BOOL animated you get 1   Hope this helps someone   Thanks   Cheers

User · Answer

you can check it by window property  if viewController view window       view visible   else      no visible

User · Answer

For over-full-screen or over-context modal presentation   is visible  could mean it is on top of the view controller stack or just visible but covered by another view controller   To check if the view controller  is the top view controller  is quite different from  is visible   you should check the view controller s navigation controller s view controller stack   I wrote a piece of code to solve this problem   extension UIViewController       public var isVisible  Bool           if isViewLoaded               return view window    nil                   return false            public var isTopViewController  Bool           if self navigationController    nil               return self navigationController  visibleViewController     self           else if self tabBarController    nil               return self tabBarController  selectedViewController    self  amp  amp  self presentedViewController    nil           else               return self presentedViewController    nil  amp  amp  self isVisible

User · Answer

I needed this to check if the view controller is the current viewed controller  I did it via checking if there s any presented view controller or pushed through the navigator  I m posting it in case anyone needed such a solution   if presentedViewController    nil    navigationController  topViewController    self           Viewcontroller isn t viewed  else          Now your viewcontroller is being viewed

User · Answer

I made a swift extension based on  progrmr s answer    It allows you to easily check if a UIViewController is on screen like so   if someViewController isOnScreen          Do stuff here     The extension          UIViewControllerExtension swift     import UIKit  extension UIViewController      var isOnScreen  Bool          return self isViewLoaded    amp  amp  view window    nil

User · Answer

There are a couple of issues with the above solutions   If you are using  for example  a UISplitViewController  the master view will always return true for   if viewController isViewLoaded  amp  amp  viewController view window          Always true for master view in split view controller     Instead  take this simple approach which seems to work well in most  if not all cases   -  void viewDidDisappear  BOOL animated        super viewDidDisappear animated          We are now invisible     self visible   false     -  void viewDidAppear  BOOL animated        super viewDidAppear animated          We are now visible     self visible   true

User · Answer

I use this small extension in Swift 5  which keeps it simple and easy to check for any object that is member of UIView    extension UIView       var isVisible  Bool           guard let     self window else               return false                   return true           Then  I just use it as a simple if statement check     if myView isVisible          do something     I hope it helps

User · Answer

For my purposes  in the context of a container view controller  I ve found that  -  BOOL isVisible       return  self isViewLoaded  amp  amp  self view window  amp  amp  self parentViewController    nil       works well

User · Answer

I found those function in UIViewController h        These four methods can be used in a view controller s appearance callbacks to determine if it is being   presented  dismissed  or added or removed as a child view controller  For example  a view controller can   check if it is disappearing because it was dismissed or popped by asking itself in its viewWillDisappear    method by checking the expression   self isBeingDismissed      self isMovingFromParentViewController        -  BOOL isBeingPresented NS AVAILABLE IOS 5 0   -  BOOL isBeingDismissed NS AVAILABLE IOS 5 0    -  BOOL isMovingToParentViewController NS AVAILABLE IOS 5 0   -  BOOL isMovingFromParentViewController NS AVAILABLE IOS 5 0     Maybe the above functions can detect the ViewController is appeared or not

User · Answer

If you are using a navigation controller and just want to know if you are in the active and topmost controller  then use   if navigationController  topViewController    self          Do something     This answer is based on  mattdipasquale s comment   If you have a more complicated scenario  see the other answers above

User · Answer

The approach that I used for a modal presented view controller was to check the class of the presented controller   If the presented view controller was ViewController2 then I would execute some code   UIViewController  vc    self presentedViewController    if   vc isKindOfClass  ViewController2 class          NSLog   this is VC2

User · Answer

You want to use the UITabBarController s selectedViewController property  All view controllers attached to a tab bar controller have a tabBarController property set  so you can  from within any of the view controllers  code   if    self tabBarController  selectedViewController  isEqual self           we re in the active controller  else         we are not

User · Answer

Here s  progrmr s solution as a UIViewController category      UIViewController Additions h   interface UIViewController  Additions   -  BOOL isVisible    end      UIViewController Additions m   import  UIViewController Additions h    implementation UIViewController  Additions   -  BOOL isVisible       return  self isViewLoaded   amp  amp  self view window      end

User · Answer

The view s window property is non-nil if a view is currently visible  so check the main view in the view controller   Invoking the view method causes the view to load  if it is not loaded  which is unnecessary and may be undesirable   It would be better to check first to see if it is already loaded   I ve added the call to isViewLoaded to avoid this problem   if  viewController isViewLoaded  amp  amp  viewController view window           viewController is visible     Since iOS9 it has became easier   if viewController viewIfLoaded  window    nil          viewController is visible       Or if you have a UINavigationController managing the view controllers  you could check its visibleViewController property instead

User · Answer

if you re utilizing a UINavigationController and also want to handle modal views  the following is what i use    import  lt objc runtime h gt   UIViewController  topMostController   self navigationController visibleViewController  if   NSString stringWithFormat    s   class getName  topMostController class    isEqualToString   NAME OF CONTROLLER YOURE CHECKING IN            is topmost visible view controller

User · Answer

For those of you looking for a Swift 2 2 version of the answer   if self isViewLoaded    amp  amp   self view window    nil            viewController is visible     and Swift 3   if self isViewLoaded  amp  amp   self view window    nil                viewController is visible

User · Answer

Good point that view is appeared if it s already in window hierarchy stack  thus we can extend our classes for this functionality  extension UIViewController     var isViewAppeared  Bool   viewIfLoaded  isAppeared    true      extension UIView     var isAppeared  Bool   window    nil

[ios] How to tell if UIViewController's view is visible

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