Swift - How to detect orientation changes

Question

I want to add two images to single image view  i e for landscape one image and for portrait another image but i don t know how to detect orientation changes using swift languages   I tried this answer but it takes only one image  override func viewWillTransitionToSize size  CGSize  withTransitionCoordinator coordinator  UIViewControllerTransitionCoordinator        if UIDevice currentDevice   orientation isLandscape boolValue           print  Landscape         else           print  Portrait             I am new to iOS development any advice would be greatly appreciated

User · Answer

I believe the correct answer is actually a combination of both approaches: viewWIllTransition(toSize:) and NotificationCenter's UIDeviceOrientationDidChange.

viewWillTransition(toSize:) notifies you before the transition.

NotificationCenter UIDeviceOrientationDidChange notifies you after.

You have to be very careful. For example, in UISplitViewController when the device rotates into certain orientations, the DetailViewController gets popped off the UISplitViewController's viewcontrollers array, and pushed onto the master's UINavigationController. If you go searching for the detail view controller before the rotation has finished, it may not exist and crash.

User · Answer

Swift 4  I ve had some minor issues when updating the ViewControllers view using UIDevice current orientation  such as updating constraints of tableview cells during rotation or animation of subviews   Instead of the above methods I am currently comparing the transition size to the view controllers view size  This seems like the proper way to go since one has access to both at this point in code   override func viewWillTransition to size  CGSize  with coordinator  UIViewControllerTransitionCoordinator        super viewWillTransition to  size  with  coordinator      print  Will Transition to size   size  from super view size   self view frame size         if  size width  gt  self view frame size width            print  Landscape         else           print  Portrait              if  size width    self view frame size width               Reload TableView to update cell s constraints         Ensuring no dequeued cells have old constraints          DispatchQueue main async               self tableView reloadData                         Output on a iPhone 6   Will Transition to size  667 0  375 0  from super view size  375 0  667 0   Will Transition to size  375 0  667 0  from super view size  667 0  375 0

User · Answer

Another way to detect device orientations is with the function traitCollectionDidChange      The system calls this method when the iOS interface environment changes   override func traitCollectionDidChange   previousTraitCollection  UITraitCollection         super traitCollectionDidChange previousTraitCollection                Furthermore  you can use function willTransition to with     which is called before traitCollectionDidChange        to get information just before the orientation is applied    override func willTransition to newCollection  UITraitCollection  with coordinator  UIViewControllerTransitionCoordinator        super willTransition to  newCollection  with  coordinator

User · Answer

let const    Background    image name let const2    GreyBackground     image name      IBOutlet weak var imageView  UIImageView      override func viewDidLoad             super viewDidLoad            imageView image   UIImage named  const             Do any additional setup after loading the view             override func viewWillTransition to size  CGSize  with coordinator  UIViewControllerTransitionCoordinator            super viewWillTransition to  size  with  coordinator          if UIDevice current orientation isLandscape               print  Landscape               imageView image   UIImage named  const2            else               print  Portrait               imageView image   UIImage named  const

User · Answer

Device Orientation    Interface Orientation   Swift 5   iOS14 and below You should really make a difference between   Device Orientation   gt  Indicates the orientation of the physical device Interface Orientation   gt  Indicates the orientation of the interface displayed on the screen  There are many scenarios where those 2 values are mismatching such as   When you lock your screen orientation When you have your device flat  In most cases you would want to use the interface orientation and you can get it via the window  private var windowInterfaceOrientation  UIInterfaceOrientation        return UIApplication shared windows first  windowScene  interfaceOrientation    In case you also want to support  lt  iOS 13  such as iOS 12  you would do the following  private var windowInterfaceOrientation  UIInterfaceOrientation        if  available iOS 13 0               return UIApplication shared windows first  windowScene  interfaceOrientation       else           return UIApplication shared statusBarOrientation          Now you need to define where to react to the window interface orientation change  There are multiple ways to do that but the optimal solution is to do it within  willTransition to newCollection  UITraitCollection  This inherited UIViewController method which can be overridden will be trigger every time the interface orientation will be change  Consequently you can do all your modifications in the latter  Here is a solution example  class ViewController  UIViewController       override func willTransition to newCollection  UITraitCollection  with coordinator  UIViewControllerTransitionCoordinator            super willTransition to  newCollection  with  coordinator                   coordinator animate alongsideTransition     context  in             guard let windowInterfaceOrientation   self windowInterfaceOrientation else   return                            if windowInterfaceOrientation isLandscape                      activate landscape changes               else                      activate portrait changes                                         private var windowInterfaceOrientation  UIInterfaceOrientation            return UIApplication shared windows first  windowScene  interfaceOrientation          By implementing this method you ll then be able to react to any change of orientation to your interface  But keep in mind that it won t be triggered at the opening of the app so you will also have to manually update your interface in viewWillAppear    I ve created a sample project which underlines the difference between device orientation and interface orientation  Additionally it will help you to understand the different behavior depending on which lifecycle step you decide to update your UI  Feel free to clone and run the following repository  https   github com wjosset ReactToOrientation

User · Answer

Swift 4   I was using this for soft keyboard design  and for some reason the UIDevice current orientation isLandscape method kept telling me it was Portrait  so here s what I used instead   override func viewWillTransition to size  CGSize  with coordinator  UIViewControllerTransitionCoordinator        super viewWillTransition to  size  with  coordinator       if size width  gt  self view frame size width             Landscape           else            Portrait

User · Answer

You can use viewWillTransition to with   and tap into animate alongsideTransition completion   to get the interface orientation AFTER the transition is complete  You just have to define and implement a protocol similar to this in order to tap into the event  Note that this code was used for a SpriteKit game and your specific implementation may differ   protocol CanReceiveTransitionEvents       func viewWillTransition to size  CGSize      func interfaceOrientationChanged to orientation  UIInterfaceOrientation      override func viewWillTransition to size  CGSize  with coordinator  UIViewControllerTransitionCoordinator            super viewWillTransition to  size  with  coordinator           guard             let skView   self view as  SKView              let canReceiveRotationEvents   skView scene as  CanReceiveTransitionEvents else   return            coordinator animate alongsideTransition  nil      in             if let interfaceOrientation   UIApplication shared windows first  windowScene  interfaceOrientation                   canReceiveRotationEvents interfaceOrientationChanged to  interfaceOrientation                                   canReceiveRotationEvents viewWillTransition to  size          You can set breakpoints in these functions and observe that interfaceOrientationChanged to orientation  UIInterfaceOrientation  is always called after viewWillTransition to size  CGSize  with the updated orientation

User · Answer

To get the correct orientation on app start you have to check it in viewDidLayoutSubviews    Other methods described here won t work   Here s an example how to do it   var mFirstStart   true  override func viewDidLayoutSubviews         super viewDidLayoutSubviews       if  mFirstStart            mFirstStart   false         detectOrientation            func detectOrientation         if UIDevice current orientation isLandscape           print  Landscape              do your stuff here for landscape       else           print  Portrait              do your stuff here for portrait          override func viewWillTransition to size  CGSize  with coordinator  UIViewControllerTransitionCoordinator        detectOrientation       This will work always  on app first start  and if rotating while the app is running

User · Answer

Swift 3  Above code updated    override func viewWillTransition to size  CGSize  with coordinator  UIViewControllerTransitionCoordinator        super viewWillTransition to  size  with  coordinator       if UIDevice current orientation isLandscape           print  Landscape         else           print  Portrait

User · Answer

If your are using Swift version    3 0 there are some code updates you have to apply as others have already said  Just don t forget to call super   override func viewWillTransition to size  CGSize  with coordinator  UIViewControllerTransitionCoordinator        super viewWillTransition to  size  with  coordinator         YOUR CODE OR FUNCTIONS CALL HERE      If you are thinking to use a StackView for your images be aware you can do something like the following   override func viewWillTransition to size  CGSize  with coordinator  UIViewControllerTransitionCoordinator        super viewWillTransition to  size  with  coordinator      if UIDevice current orientation isLandscape          stackView axis    horizontal       else          stackView axis    vertical          else      If your are using Interface Builder don t forget to select the custom class for this UIStackView object  in the Identity Inspector section at the right panel  Then just create  also through Interface Builder  the IBOutlet reference to the custom UIStackView instance    IBOutlet weak var stackView  MyStackView    Take the idea and adapt it to your needs  Hope this can help you

User · Answer

Swift 4 2  RxSwift   If we need to reload collectionView   NotificationCenter default rx notification UIDevice orientationDidChangeNotification       observeOn MainScheduler instance       map     in                    bind to  collectionView rx reloadData       disposed by  bag    Swift 4  RxSwift   If we need to reload collectionView   NotificationCenter default rx notification NSNotification Name UIDeviceOrientationDidChange       observeOn MainScheduler instance       map     in                    bind to  collectionView rx reloadData       disposed by  bag

User · Answer

All previous contributes are fine  but a little note   a  if orientation is set in plist  only portrait or example  You will be not notified via viewWillTransition  b  if we anyway need to know if user has rotated device   for example a game or similar    we can only use   NotificationCenter default addObserver self  selector   selector ViewController rotated   name  NSNotification Name UIDeviceOrientationDidChange  object  nil    tested on Xcode8  iOS11

User · Answer

Using NotificationCenter and UIDevice s beginGeneratingDeviceOrientationNotifications  Swift 4 2   override func viewDidLoad         super viewDidLoad                NotificationCenter default addObserver self  selector   selector ViewController rotated   name  UIDevice orientationDidChangeNotification  object  nil     deinit      NotificationCenter default removeObserver self  name  UIDevice orientationDidChangeNotification  object  nil              func rotated         if UIDevice current orientation isLandscape           print  Landscape         else           print  Portrait             Swift 3  override func viewDidLoad         super viewDidLoad                NotificationCenter default addObserver self  selector   selector ViewController rotated   name  NSNotification Name UIDeviceOrientationDidChange  object  nil     deinit        NotificationCenter default removeObserver self     func rotated         if UIDevice current orientation isLandscape           print  Landscape         else           print  Portrait

[ios] Swift - How to detect orientation changes

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