Question

I have a UITabBarController controlling a couple MKMapViews. How would I keep their state persistent with one another? I’ve tried setting up a singleton pattern, but they are still independent.

Answer 1

I see two possible solutions for your problem

1. You instantiate one (1x) MKMapView in a controller (maybe a singleton). Let’s say in your AppDelegate you have one MKMapView instance.

   • You use a UIViewController instance per Tab (so: many UIViewControllers but only one MKMapView in a controller.
   • You listen for - (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController at your tabbar controller delegate.
   • when the user changes the tab, you place the single (1x) MKMapView on the appearing UIViewController’s view.

   • But here you will have the same content (Annotations, Regions, data at all)

      

2. You can synchronize many MKMapView

   • Listen for MKMapView delegates (– mapView:regionWillChangeAnimated:, etc.) and synchronize the values to you other MKMapViews. You need to do that by Notifications (NSNotification) or by a controller.
   • this would give you more flexibility which values you’d like to sync and which values must be different from MKMapView to MKMapView.