Detect iOS app entering background
I'm working on a game for iOS coded in Swift. I've tried to find a way to detect when the app enters background mode or is interrupted for other reasons, for example a phone call but can't find anything. How do I do it?
Solution 1:
You can add an observer to your view controller:
edit/update: Xcode 11 • Swift 5
iOS13 or later
UIScene.willDeactivateNotification
iOS12 or earlier
UIApplication.willResignActiveNotification
if #available(iOS 13.0, *) {
NotificationCenter.default.addObserver(self, selector: #selector(willResignActive), name: UIScene.willDeactivateNotification, object: nil)
} else {
NotificationCenter.default.addObserver(self, selector: #selector(willResignActive), name: UIApplication.willResignActiveNotification, object: nil)
}
and add a selector method to your view controller that will be executed when your app receives that notification:
@objc func willResignActive(_ notification: Notification) {
// code to execute
}
Solution 2:
In swift 5.x: To observe app enters background event, add this code to your viewDidLoad() method.
let notificationCenter = NotificationCenter.default
notificationCenter.addObserver(self, selector: #selector(appMovedToBackground), name: UIApplication.didEnterBackgroundNotification, object: nil)
@objc func appMovedToBackground() {
// do whatever event you want
}
you have to use UIApplication.didEnterBackgroundNotification
.
If you want to observe if app came to foreground event, use UIApplication.willEnterForegroundNotification
So, the full code will be:
override func viewDidLoad() {
super.viewDidLoad()
let notificationCenter = NotificationCenter.default
notificationCenter.addObserver(self, selector: #selector(appMovedToBackground), name: UIApplication.didEnterBackgroundNotification, object: nil)
notificationCenter.addObserver(self, selector: #selector(appCameToForeground), name: UIApplication.willEnterForegroundNotification, object: nil)
// Do any additional setup after loading the view.
}
@objc func appMovedToBackground() {
print("app enters background")
}
@objc func appCameToForeground() {
print("app enters foreground")
}
Solution 3:
Swift3
let notificationCenter = NotificationCenter.default
notificationCenter.addObserver(self, selector: #selector(appMovedToBackground), name: Notification.Name.UIApplicationWillResignActive, object: nil)
func appMovedToBackground() {
print("App moved to background!")
}
Solution 4:
SwiftUI
From background
Text("Hello, World!")
.onReceive(NotificationCenter.default.publisher(for: UIApplication.willEnterForegroundNotification)) { _ in
print("To the foreground!")
}
To the background
Text("Hello, World!")
.onReceive(NotificationCenter.default.publisher(for: UIApplication.willResignActiveNotification)) { _ in
print("To the background!")
}