Why is my CLLocationManager not responding to startMonitoringForRegion? - ios

Question

At the bottom (in AppDelegate.m) you can see my CLLocationManager delegate methods, none of them get called. I'm using a GPX file, but even if the regions do not get entered or exited, the delegate method didStartMonitoringForRegion should be called.
SomeOtherClass.m
AppDelegate appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
[appDelegate.locationManager startMonitoringForRegion:regionToMonitor desiredAccuracy:kCLLocationAccuracyNearestTenMeters];
AppDelegate.h
#interface AppDelegate : UIResponder <UIApplicationDelegate,CLLocationManagerDelegate>
#property (nonatomic, retain) CLLocationManager *locationManager;
AppDelegate.m
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
if (locationManager==nil) {
locationManager = [[CLLocationManager alloc] init];
locationManager.delegate = self;
}
return YES;
}
-(void)locationManager:(CLLocationManager *)manager didEnterRegion:(CLRegion *)region {
NSLog(#"Did enter region");
}
-(void)locationManager:(CLLocationManager *)manager didExitRegion:(CLRegion *)region {
NSLog(#"Did exit region");
}
-(void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error {
NSLog(#"Fail");
NSLog(#"%#", [error description]);
}
-(void)locationManager:(CLLocationManager *)manager didStartMonitoringForRegion:(CLRegion *)region {
NSLog(#"Did start monitoring for region: %#", region.identifier);
}

Answer 1

First of all you should add the following Location manager delegate method, and see if for some reason the region monitoring registration failed:
- (void)locationManager:(CLLocationManager *)manager monitoringDidFailForRegion:(CLRegion *)region withError:(NSError *)error {
NSLog(#"%#",error);
}
Second, the region monitoring is a system shared resource.
The documentation states that it allows you limited number of regions to monitor (not specifying any number unfortunately) and mentioning that if another app register additional regions to monitor, some of your apps monitored regions, might be discarded.
Third, region monitoring is not using any GPS technology. It only uses the cellular antenna of your network operator and whenever you change a cell tower, it fires an system event that loops through all monitored regions and see if a region is within the new area you are now located.
This means that you should expect less accuracy in the service and therefore you should increase the radius you are setting for a region.
Finally if your app is completely terminated and NOT suspended, then your app will receive in the app delegate inside the:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
a UIApplicationLaunchOptionsLocationKey in the launchOptions dictionary.
It's your responsibility then to reinitialize your location manager, get the current location and fire a local push notification to the user, within the limited time your application live state has.
As the app is not going to run normally at that stage, but in a limited background mode state.
Also if you want to test the app in the simulator, you should add a track.gpx file to your project and set the simulator to track mode.
Make sure that the 2 locations you put in the simulator are not very distant (as it might take quite long time for the tracking to complete) and set them in a path, where it will enter your monitored region.
Then see if you get any callbacks.
Do not test it with your device, as you need to actually walk a couple of blocks to see any real interaction with the device :-)

Answer 2

Not entirely sure why it wouldn't receive your callbacks. I'll cover a few things I'm noticing and you can see if they help.
You are not setting the desiredAccuracy or distanceFilter in your location manager. They should default to something, but if your locations in the GPX aren't within the accuracy of the regions, it could just be not getting close enough to trigger.
The method you are using to start monitoring has been deprecated in iOS 6. You can add the accuracy to the location manager and leave that off your call.
It would be helpful to see how you are creating your CLRegion to monitor, regionToMonitor. If it is being created ok as soon as you start monitoring, you should see the hollow purple location arrow show up. You should also receive the delegate call -didStartMonitoringForRegion. If neither of these are showing up, then you probably just have an issue with your location manager setup.
One suggestion would be to create your own location manager class and turn it into a singleton. This will prevent you from accidentally initializing multiple delegates and getting multiple calls. It also gives you one clean class to contain all your callback methods.
I don't see anything wrong with the code you've included, so I'm guessing the problem lies in the code you haven't included. Check to make sure your location manager code is being initialized and make sure your CLRegion is being created correctly. Hope this helps. I'll be happy to update my answer if you include more code and we find out what the true issue is.