applicationDidEnterBackground(_:)
Tells the delegate that the app is now in the background.
Declaration
optional func applicationDidEnterBackground(_ application: UIApplication)Parameters
- application:
Your singleton app object.
Mentioned in
Discussion
Use this method to release shared resources, invalidate timers, and store enough app state information to restore your app to its current state in case it’s terminated later. Disable updates to your app’s user interface, and avoid using some types of shared system resources (such as the user’s contacts database). Don’t use OpenGL ES in the background.
Return from applicationDidEnterBackground(_:) as quickly as possible. Your implementation of this method has approximately five seconds to perform any tasks and return. If the method doesn’t return before time runs out, your app is terminated and purged from memory.
If you need additional time to perform any final tasks, request additional execution time from the system by calling beginBackgroundTask(expirationHandler:). Call beginBackgroundTask(expirationHandler:) as early as possible. Because the system needs time to process your request, there’s a chance that the system might suspend your app before that task assertion is granted. For example, don’t call beginBackgroundTask(expirationHandler:) at the very end of your applicationDidEnterBackground(_:) method and expect your app to continue running.
Perform any tasks related to adjusting your user interface before applicationDidEnterBackground(_:) exits. Move other tasks (such as saving state) to a concurrent dispatch queue or secondary thread as needed. Because it’s likely any background tasks you start in applicationDidEnterBackground(_:) won’t run until after that method exits, request additional background execution time before starting those tasks. In other words, first call beginBackgroundTask(expirationHandler:) and then run the task on a dispatch queue or secondary thread.
UIKit also posts a didEnterBackgroundNotification around the same time it calls this method to give interested objects a chance to respond to the transition.
For more information about how to transition gracefully to the background, and for information about how to start background tasks, see App Programming Guide for iOS.