How can I check when an app comes back into the foreground from the background, but not from push notification?

Question

func application(application: UIApplication, didReceiveRemoteNotification data: [NSObject : AnyObject]) {
        var dat = JSON(data)
        if application.applicationState == UIApplicationState.Active {
            // app was already in the foreground
            println("App is in foreground")
            processNotification(dat)
        }else{
            // app was just brought from background to foreground via PUSH
            println("App brought back via PUSH")
            processNotification(dat)
        }
    }

This is how I check for push notifications. However, when if I send a push notification, the user misses it, and then opens the app via the icon? How can I check when the app was opened from the icon?

Answer 1

The UIApplicationDelegate protocol defines several methods that let you add code to several of your application's life cycle events.

Of specific interest to you would be the following:

• application(_:willFinishLaunchingWithOptions:) - called just before the application has finished launching when the application was not already active in the background
• application(_:didFinishLaunchingWithOptions:) - called just after the application has finished launching when the application was not already active in the background
• applicationDidBecomeActive(_:) - called just after the application has become active, this is called when the user launches from scratch, reopens from background, and also when a user returns from a temporary interruption (such as a phone call)
• applicationWillEnterForeground(_:) - this is called just before the application enters the foreground after having been in the background--it is immediately followed by the applicationDidBecomeActive(_:) call

This life cycle events can fire whether the user opened your application via a notification or by tapping on the icon. As far as I know there is no way to tell for certain that the application was opened via tapping the icon. You can know(ish) that the application wasn't opened via a notification, as the relevant "did receive notification" methods will never fire. But this still allows the user two (at least) methods of opening the application: tapping the app icon or double tapping the home button and tapping the app to awake it from the background.