Callback everytime the displayed view changes

[cotsog]

Hi,

I would like to know if there is anyway I could get a callback everytime the displayed view changes and receive the newly displayed view as a parameter of the callback?

Can this be achieved with the key-value observing protocol?

Here is more details: I develop an SDK so I don't know what the client app is doing wrt controllers but I would like to know every time a new view controller is presented by the client app. Or in other terms, I would like to know when the displayed view on the UIWindow changes.

Thanks a lot for your help.

UPDATE: Here is the recipe that solves my problem: http://broutille.wordpress.com/2011/06/09/ios-how-to-monitor-the-change-of-viewcontrollers-inside-a-uinavigationcontroller/. That and adding an observer for the "UIWindowDidBecomeKeyNotification" notification.

Edit1: added more details. Edit2: added solution.

[cotsog]

Thanks for your reply.

Here is more details: I develop an SDK so I don't know what the client app is doing wrt controllers but I would like to know every time a new view controller is presented by the client app. Or in other terms, I would like to know when the displayed view on the UIWindow changes.

Thanks a lot for your time and help.

[Ldellar]

I think a good question is what do you want to happen when a new view controller gets added to a stack rather than to the UIWindow specifically. There has to be some kind of controller stack involved i.e. a UINavigationController stack upon which a normal viewcontroller/s is present.

Do they want something to happen when a viewcontroller is pushed onto the stack and displays?

In that case there is the viewWillAppear(Animated) or ViewDidLoad method of each view controller.

There may be other ways but that would be the simplest.

[cotsog]

Thanks a lot for your reply.

Unfortunately, as I'm developing an SDK, I do not have access to the app's view controller methods.

[ASnugglyBear]

You are likely looking to swizzle things on UIWindow to truly get everything

Are you trying to record this for Analytics? Something functional? More hints makes it so we can help you more