Swift & Xcode IOS App: limit time app is running in background - swift

Question

I would like to know how to limit the time my app is running in background.
The purpose is to show the LaunchScreen again and start the app from initial state after 5 or 10 minutes in background run.
thanks in advance

Answer 1

Here are some ideas and thoughts to achieve what you want.
First, when your app moves into the background, it makes a call to applicationDidEnterBackground(_:) in your App Delegate. If you are using scenes with a Scene Delegate then you should perform any last logic in sceneDidEnterBackground(_:)
As per the docs, you have 5 seconds to perform any task once the above functions have been called
applicationDidEnterBackground(_:)
Return from applicationDidEnterBackground(_:) as quickly as possible.
Your implementation of this method has approximately five seconds to
perform any tasks and return.
After this, your app goes into a suspended state and if you need more than 5 seconds, you can request more by calling beginBackgroundTask(withName:expirationHandler:) but for your purposes I don't think you need this.
More on the above topics here
You have little to no control on when your app gets to run on the background again, that is moved from a suspended to a background state.
There is a property for BGTaskRequest called earliestBeginDate but as per the docs:
earliestBeginDate
Specify nil for no start delay.
Setting the property indicates that the background task shouldn’t
start any earlier than this date. However, the system doesn’t
guarantee launching the task at the specified date, but only that it
won’t begin sooner.
So long story short, you can't really tell when your app will get to run on the background again and you can't decide how much time it will be given to run.
What you could do is implement either applicationDidEnterBackground(_:) or sceneDidEnterBackground(_:) if you are using scenes to track at what time the app goes into the background like so:
func sceneDidEnterBackground(_ scene: UIScene)
{
// Get the current date / time
let currentDate = Date()
let userDefaults = UserDefaults.standard
// Start tracking time as soon as the app goes
// into the background
userDefaults.setValue(currentDate,
forKey: "PreviousLaunchDate")
// Just for testing, remove from production app
print("start tracking")
}
And then when your app comes into the the foreground, check how much time has elapsed and react accordingly:
func sceneWillEnterForeground(_ scene: UIScene)
{
let userDefaults = UserDefaults.standard
let currentDate = Date()
// Check if you have saved a date before
if let previousLaunchDate
= userDefaults.object(forKey: "PreviousLaunchDate") as? Date
{
// Retrieve the minutes elapsed
// Check if minutes elapsed is greater than 10 minutes or as you wish
if let minutesElapsed = Calendar.current.dateComponents([.minute],
from: previousLaunchDate,
to: currentDate).minute,
minutesElapsed > 10
{
// Reset your window's root view controller to start again
// showing the splash view or reset your storyboard etc
// For example
// let splashVC = SplashViewController()
// window?.rootViewController = splashVC
// just for testing, remove from production app
print("show splash vc")
return
}
// Do nothing since 10 minutes haven't elapsed so you can
// show the current state of the app to the user
// just for testing, remove from production app
print("do nothing")
}
}
I think this should get you close to what you are looking for.