Making NSTimer run in the background on a physical device - ios

Question

I have a timer app that I have made.
When I run it on the iPhone X on the simulator, the timer will run in the background just fine, but when I test it on my physical device (iPad Pro), it does not run in the background.
When I say in the background, I mean when you press the off button located on the top (iPad)/side (iPhone) of the device, so that the screen goes black.
Is this a glitch on the simulator's behalf, or something that I am not aware of, or is there something I need to change about my app to make it work in the background on PHYSICAL DEVICES as well?
Thanks

Answer 1

In DidBackground:
stop normalTimer.
start New backgroundTaskTimer
In WillForeground:
stop backgroundTaskTimer.
start normalTimer
Find below sample code:
In Appdelegate:
Declaration:
var backgroundUpdateTask: UIBackgroundTaskIdentifier!
var backgroundTaskTimer:Timer! = Timer()
Implementation:
func doBackgroundTask() {
DispatchQueue.global(qos: .default).async {
self.beginBackgroundTask()
if self.backgroundTaskTimer != nil {
self.backgroundTaskTimer.invalidate()
self.backgroundTaskTimer = nil
}
//Making the app to run in background forever by calling the API
self.backgroundTaskTimer = Timer.scheduledTimer(timeInterval: 10, target: self, selector: #selector(self.startTracking), userInfo: nil, repeats: true)
RunLoop.current.add(self.backgroundTaskTimer, forMode: RunLoopMode.defaultRunLoopMode)
RunLoop.current.run()
// End the background task.
self.endBackgroundTask()
}
}
func beginBackgroundTask() {
self.backgroundUpdateTask = UIApplication.shared.beginBackgroundTask(withName: "Track trip", expirationHandler: {
self.endBackgroundTask()
})
}
func endBackgroundTask() {
UIApplication.shared.endBackgroundTask(self.backgroundUpdateTask)
self.backgroundUpdateTask = UIBackgroundTaskInvalid
}
In ApplicationDidEnterBackground:
func applicationDidEnterBackground(_ application: UIApplication) {
//Start the background fetch
self.doBackgroundTask()
}
In ApplicationWillEnterForeground:
func applicationWillEnterForeground(_ application: UIApplication) {
if self.backgroundTaskTimer != nil {
self.backgroundTaskTimer.invalidate()
self.backgroundTaskTimer = nil
}
}