How to check if location services are enabled for a particular app prior to iOS 4.2?

Question

How can I check if the user has allowed location for mu app? Normally I would use authorizationStatus method of the CLLocationManager class, but it is only available in iOS 4.2 and newer. Is it possible to achieve this somehow while still using SDK 4.2, so that the app can still run on devices with older versions of iOS, or do I have to downgrade the SDK? And along the same line, I need a similar alternative for the locationServicesEnabled method prior to iOS 4.0.

Bunyip

Answer 1

When you call -startUpdatingLocation, if location services were denied by the user, the location manager delegate will receive a call to -locationManager:didFailWithError: with the kCLErrorDenied error code. This works both in all versions of iOS.

Mach

I like calling [CLLocationManager locationServicesEnabled] as described below better. That way you can prevent unnecessary calls. – Razzledazzle

For users who stumble here without the 'prior iOS 4.2' constraint, the answer is: [CLLocationManager authorizationStatus] – Brinkmanship

@Razzledazzle does this answer the question though? OP asked how to determine if location services enabled for a particular app and [CLLocationManager locationServicesEnabled] just tests for device wide location services. [CLLocationManager authorizationStatus] tests for app specific authorization. – Canna

@SpacyRicochet, [CLLocationManager locationServicesEnabled] only checks the general "Location Services" switch, it does not check the single app's status. – Suckling

@nous Now it's kCLAuthorizationStatusDenied – Unarm

Answer 2

I've combined two techniques in the code below

    MKUserLocation *userLocation = map.userLocation;
    BOOL locationAllowed = [CLLocationManager locationServicesEnabled];
    BOOL locationAvailable = userLocation.location!=nil;

    if (locationAllowed==NO) {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Location Service Disabled" 
                                                        message:@"To re-enable, please go to Settings and turn on Location Service for this app." 
                                                       delegate:nil 
                                              cancelButtonTitle:@"OK" 
                                              otherButtonTitles:nil];
        [alert show];
        [alert release];
    } else {
        if (locationAvailable==NO) 
            [self.map.userLocation addObserver:self forKeyPath:@"location" options:(NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld) context:nil];
    }

Dutchman

Same problem as above. Please do not assume that a nil user location corresponds to no authorization because that might not be true. – Nummary

I think this is not so correct. [CLLocationManager locationServicesEnabled] tells you that Location is On or Off to all apps and [CLLocationManager authorizationStatus] tells if app has authorization to check location. So UIAlertView should say to turn location on and not to authorize app. But it was useful, thank you @Dutchman – Formalin

Answer 3

Hmm.. I didn't think to use authorizationStatus or locationServicesEnabled. What I did was the following:

MKUserLocation *userLocation = mapView.userLocation;

if (!userLocation.location) {
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Location Service Disabled" 
                                                    message:@"To re-enable, please go to Settings and turn on Location Service for this app." 
                                                   delegate:nil 
                                          cancelButtonTitle:@"OK" 
                                          otherButtonTitles:nil];
    [alert show];
    [alert release];
    return;
}

I'm glad to see there's a better method to check, but I haven't had any problems with the way I detect if my app is allowed to use the GPS.

Hope this helps!

Alkyne

Note that the user location may not be available even though location services are enabled. For example, the user may be outside of coverage for all sensors (e.g. an iPod touch with no Wi-Fi on). – Nummary