Question

I am developing an iOS application where need to do some stuff when I have Internet connection and other, when I haven’t. If I haven’t at some point I will show a message to the user to give me internet and come back. The question it is how to detect the following situation:

• the user press the Home button twice, goes to multitasking , Settings and will connect to internet
• the user comes back with multitasking to my app, but doesn’t press anything

I know I will get callbacks to the AppDelegate:

- (void)applicationDidEnterBackground:(UIApplication *)application
- (void) applicationDidBecomeActive:(UIApplication *)application

but the code ( it is not started by me) it is very big, and I don’t want to handle there the UIViewController needs, if there is any alternative.

My UIViewController’s – (void)viewDidAppear:(BOOL)animated it isn’t called when the user came back.

The breakpoint it is not hited for sure!

Any usable ideas, except in AppDelegate?

Answer 1

You can use the notification center to listen to applicationDidEnterBackground within the view controller:

[[NSNotificationCenter defaultCenter] addObserver: self
                                      selector: @selector(handleEnteredBackground:) 
                                      name: UIApplicationDidEnterBackgroundNotification
                                      object: nil];

Do this in viewDidLoad. Similarily for applicationDidBecomeActive.

Don’t forget to remove yourself as an observer in viewDidUnload.