location manager giving null coordinates

问题

The following code results in null coordinates. The weird thing is the UIAlert prompting the app to use current location appears briefly before the user can select yes.

My code which i have used :

CLLocationManager *locationManager;
locationManager.desiredAccuracy = kCLLocationAccuracyBest;
[locationManager startUpdatingLocation];
locationManager = [[CLLocationManager alloc] init];
locationManager.distanceFilter = kCLDistanceFilterNone;
locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters;
[locationManager startUpdatingLocation];
float latitude = locationManager.location.coordinate.latitude;
float longitude = locationManager.location.coordinate.longitude;
NSLog(@"%.8f",latitude);
NSLog(@"%.8f",longitude);

The NSLog prints 0.0000000 for both coordinates.

Thanks!

回答1:

The reason you're getting 0 is because the location manager hasn't collected any data at that point (it has started thought)

You need to set your class as the delegate of the location manager (ie supplying a function that is called whenever a new location is retrieved), and also retain your location manager.

// Inside .m file

@interface MyClass () <CLLocationManagerDelegate> // Declare this class to implement protocol CLLocationManagerDelegate

@property (strong, nonatomic) CLLocationManager* locationManager; // Retains it with strong keyword

@end

@implementation MyClass

// Inside some method

   self.locationManager = [[CLLocationManager alloc] init];
   self.locationManager.delegate = self;
   self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;
   self.locationManager.distanceFilter = kCLDistanceFilterNone;
   [self.locationManager startUpdatingLocation];

// Delegate method
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations {
    CLLocation* loc = [locations lastObject]; // locations is guaranteed to have at least one object
    float latitude = loc.coordinate.latitude;
    float longitude = loc.coordinate.longitude;
    NSLog(@"%.8f",latitude);
    NSLog(@"%.8f",longitude);
}

来源：https://stackoverflow.com/questions/19603830/location-manager-giving-null-coordinates

标签

ios

xcode

core-location