Xamarin iOS - Handling Geofence intersection triggers after terminating an app - ios

Question

I am trying to handle geofence intersection triggers when my app is terminated (not background). I want handle the enter/exit triggers from CLLocationManager even if my app is not running. It should wake up my app at the background, do the required processing on enter/exit.
To do this, a lot of places its given that it is possible using background app refresh functionality. I have the following code written but as soon as i terminate the application, it stops hearing the geofence trigger events.
Can anybody please guide me how to handle these events even if application is terminated ?
public async Task StartLocationUpdates()
{
_cts = new CancellationTokenSource();
_taskId = UIApplication.SharedApplication.BeginBackgroundTask("LongRunningTask", OnExpiration);
try
{
if (CLLocationManager.LocationServicesEnabled)
{
LocMgr.DesiredAccuracy = 1;
LocMgr.LocationsUpdated += (object sender, CLLocationsUpdatedEventArgs e) =>
{
var locations = e.Locations;
};
LocMgr.StartUpdatingLocation();
if (CLLocationManager.LocationServicesEnabled)
{
if (CLLocationManager.Status != CLAuthorizationStatus.Denied)
{
if (CLLocationManager.IsMonitoringAvailable(typeof(CLCircularRegion)))
{
LocMgr.DidStartMonitoringForRegion += (o, e) =>
{
Console.WriteLine("Now monitoring region {0}", e.Region.ToString());
};
LocMgr.RegionEntered += (o, e) =>
{
Instance.Speak("Just entered " + e.Region.ToString());
};
LocMgr.RegionLeft += (o, e) =>
{
Instance.Speak("Just left " + e.Region.ToString());
};
foreach (CLCircularRegion region in RegionList)
{
if (region != null)
{
StopMonitoringRegion(region);
}
LocMgr.StartMonitoring(region);
}
}
else
{
Console.WriteLine("This app requires region monitoring, which is unavailable on this device");
}
LocMgr.Failed += (o, e) =>
{
Console.WriteLine(e.Error);
};
}
else
{
Console.WriteLine("App is not authorized to use location data");
}
}
else
{
Console.WriteLine("Location services not enabled, please enable this in your Settings");
}
}
}
catch (OperationCanceledException)
{
}
}
Thank You in advance.

Answer 1

It seems you have added the privacy keys in the info.plist to enable the location service. If you want to enable it when the app is on background state or terminated, we also should turn on the Background Modes: Capabilities > Background Modes > Location updates.
Then we can initialize the location manager in AppDelegate:
CLLocationManager locationManager;
public override bool FinishedLaunching(UIApplication application, NSDictionary launchOptions)
{
locationManager = new CLLocationManager();
locationManager.Delegate = new MyLocationDelegate();
//enable service when app is on background or terminated
locationManager.PausesLocationUpdatesAutomatically = false;
locationManager.AllowsBackgroundLocationUpdates = true;
locationManager.RequestAlwaysAuthorization();
locationManager.DistanceFilter = 100.0;
locationManager.DesiredAccuracy = 1;
// The important request can awake your app
locationManager.StartMonitoringSignificantLocationChanges();
locationManager.StartUpdatingLocation();
return true;
}
The event LocationsUpdated() will also fire if your location has been changed even your app has been terminated:
public class MyLocationDelegate : CLLocationManagerDelegate
{
public override void LocationsUpdated(CLLocationManager manager, CLLocation[] locations)
{
//Handle your method here
}
}
You can test this with your simulator: Debug > Location > Freeway Drive. Store the locations to your sandbox folder in the event above. Force quit your app, after a few seconds open it, retrieve the file you stored. You will find the whole locations records.