sceneWillEnterForeground

sceneWillEnterForeground is a method in the UISceneDelegate protocol that is called when a scene transitions from the background to the foreground. It is part of the multi-scene lifecycle introduced in iOS 13, and it operates at the level of individual scenes rather than the application as a whole. This method is invoked before the scene becomes active and interactive.

In practice, sceneWillEnterForeground is used to prepare the scene for user interaction after it was in the background. Developers may refresh data that could have changed while the app was inactive, reestablish network connections, re-enable features that were paused, or update the user interface to reflect the current state of the app. It serves as a pre-activation hook, occurring after sceneDidEnterBackground and before sceneDidBecomeActive.

The typical usage involves implementing the method in the scene’s delegate, for example:

func sceneWillEnterForeground(_ scene: UIScene) {

// Perform lightweight tasks to prepare the UI

}

While it can be safe to perform some quick data refreshes here, long-running work should be avoided. Time-consuming tasks are better suited for background execution or deferred to sceneDidBecomeActive or other appropriate lifecycle events.

Relation to other lifecycle events: sceneWillEnterForeground is complemented by sceneDidBecomeActive, which is called when the scene actually gains focus and starts receiving events. It is distinct from applicationWillEnterForeground in UIApplicationDelegate, as the latter applies to the app as a whole, whereas the scene method applies to an individual scene.