Question

I’m looking for a way to get a background location update every n minutes in my iOS application. I’m using iOS 4.3 and the solution should work for non-jailbroken iPhones.

I tried / considered following options:

• CLLocationManager startUpdatingLocation/startMonitoringSignificantLocationChanges: This works in the background as expected, based on the configured properties, but it seems not possible to force it to update the location every n minutes
• NSTimer: Does work when the app is running in the foreground but doesn’t seem to be designed for background tasks
• Local notifications: Local notifications can be scheduled every n minutes, but it’s not possible to execute some code to get the current location (without the user having to launch the app via the notification). This approach also doesn’t seem to be a clean approach as this is not what notifications should be used for.
• UIApplication:beginBackgroundTaskWithExpirationHandler: As far as I understand, this should be used to finish some work in the background (also limited in time) when an app is moved to the background rather than implementing “long-running” background processes.

How can I implement these regular background location updates?

Answer 1

I found a solution to implement this with the help of the Apple Developer Forums:

• Specify location background mode
• Create an NSTimer in the background with UIApplication:beginBackgroundTaskWithExpirationHandler:
• When n is smaller than UIApplication:backgroundTimeRemaining it will work just fine. When n is larger, the location manager should be enabled (and disabled) again before there is no time remaining to avoid the background task being killed.

This works because location is one of the three allowed types of background execution.

Note: I lost some time by testing this in the simulator where it doesn’t work. However, it works fine on my phone.