I have View A, when the user clicks a button I pop up View B. When the user dismisses View B, and we return to View A I would like to refresh a label on View A, but is there an event that I can use to detect that we have returned to View B? I know that ViewDidLoad doesn't fire again.
+2
A:
I'm confused about the views in your question, but you might look into the NSNotificationCenter.
In this case, you would post an NSNotification event when the user dismisses View B.
Views A and B can register with the notification center to listen for this dismissal notification, calling a selector (method) when this notification is heard.
In this method, you might update a label's state or do anything else that involves updating the application state.
Likewise, you might post a notification when View B is popped-up, and have other classes register for that notification type.
More information about NSNotificationCenter is located on Apple's documentation site.
Alex Reynolds
2010-01-31 20:26:55
Interesting, thanks! Apologies for the confusion, I'm still getting used to the appropriate lingo.
Driss Zouak
2010-01-31 21:01:42
+1
A:
It sounds like you may be referring to UIViewControllers, rather than UIViews, correct? In that case, you can use -viewWillDisappear: (BOOL) animated and -viewDidDisappear: (BOOL) animated to determine when your viewController is-about-to-be/was-just-dismissed. These should be implemented on View B in your example. If you want to find out when View A is visible again, you can use -viewWillAppear: and -viewDidAppear.
Ben Gottlieb
2010-01-31 20:50:29
Yes, UIViewControllers. However I find that the ViewWillAppear and ViewDidAppear does not get fired on View A when View B is dismissed (i.e. this.View.RemoveFromSuperview(); ). I checked this by putting Console.WriteLine statements in my View A for both event handlers, and they only fire the first time that View A appears.
Driss Zouak
2010-01-31 21:08:37
That's correct; to get these to fire, you need to be using a UINavigationController (or UITabBarController)
Ben Gottlieb
2010-01-31 21:16:59
So then I presume the only way is the NSNotificationCenter. is that correct? Is that going to actually allow View A to update a label on itself after View B has done RemoveFromSuperview? I'm concerned that the way that View A would get notified would be when View A has the label instantiated. An example of this is passing a reference to View B of View A and giving View A a property to access such a label, if View B tries to update it the label is null because View A's label isn't currently instantiated.
Driss Zouak
2010-01-31 23:39:25
Additional question, how do you do this with the UINavigationController?
Driss Zouak
2010-02-01 01:17:48