Why is this code updating location twice every time? - objective-c

Question

Here is the code, it all works fine but each time I hit the "Get My Location" button it updates the location twice, I cannot find the reason why, any idea's? I have removed much code from below this and it still does it so I know it's in this part somewhere. Thanks.
.h file:
#import <CoreLocation/CoreLocation.h>
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController
#property (weak, nonatomic) IBOutlet UILabel *LatitudeLabel;
#property (weak, nonatomic) IBOutlet UILabel *LongitudeLabel;
#property (weak, nonatomic) IBOutlet UILabel *GPSAccuracyLabel;
#property (weak, nonatomic) IBOutlet UILabel *AltitudeLabel;
#property (weak, nonatomic) IBOutlet UILabel *VerticalAccuracyLabel;
- (IBAction)getCurrentLocation:(id)sender;
#end
#interface MyLocationViewController : UIViewController <CLLocationManagerDelegate>
#end
.m file:
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController {
CLLocationManager *locationManager;
}
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
locationManager = [[CLLocationManager alloc] init];
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)getCurrentLocation:(id)sender {
locationManager.delegate = (id)self;
locationManager.desiredAccuracy = kCLLocationAccuracyBest;
[locationManager startUpdatingLocation];
}
#pragma mark - CLLocationManagerDelegate
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
NSLog(#"didFailWithError: %#", error); UIAlertView *errorAlert = [[UIAlertView alloc] initWithTitle:#"Error" message:#"Failed to Get Your Location" delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil]; [errorAlert show];
}
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
NSLog(#"Location updated: %#", newLocation);
CLLocation *currentLocation = newLocation;
if (currentLocation != nil) {
_LatitudeLabel.text = [NSString stringWithFormat:#"%.8f", currentLocation.coordinate.latitude];
_LongitudeLabel.text = [NSString stringWithFormat:#"%.6f", currentLocation.coordinate.longitude];
_GPSAccuracyLabel.text = [NSString stringWithFormat:#"%.2f", currentLocation.horizontalAccuracy];
_AltitudeLabel.text = [NSString stringWithFormat:#"%.2f", currentLocation.altitude];
_VerticalAccuracyLabel.text = [NSString stringWithFormat:#"%.2f", currentLocation.verticalAccuracy];
}
Console output each time I press the button:
2014-11-22 23:49:37.539 MyLocationDemo[914:60b] Location updated: <+10.16863927,+124.75859298> +/- 10.00m (speed 0.00 mps / course -1.00) # 22/11/14 11:49:37 pm Philippine Standard Time
2014-11-22 23:49:37.545 MyLocationDemo[914:60b] Location updated: <+10.16863927,+124.75859298> +/- 10.00m (speed 0.00 mps / course -1.00) # 22/11/14 11:49:37 pm Philippine Standard Time

Answer 1

After a quick look at Apple's documentations, I've noticed that the delegate method you are using, - locationManager:didUpdateToLocation:fromLocation: is deprecated since iOS 6.
Instead, you should use - locationManager:didUpdateLocations:.
Try replacing your code with the code below and see if it make any difference:
EDIT- I've edit the code below to handle the double-call you get.
From your post above I see they are almost simultaneously, So basically we'll check if at least 1 seconds has passed since last call.
There are probably better ways to do it, but that was just at the top of my head...
Haven't checked it in Xcode, but, if I haven't made a typo or something, it should work.
// ViewController.m
#interface ViewController ()
#property (nonatomic, strong) NSDate *lastUpdateTime; // Create a property
#end // to hold current time
- (void)viewDidLoad {
[super viewDidLoad];
self.lastUpdateTime = [NSDate date]; // In viewDidLoad, 'initialize' it
// to get the current time
}
- (void)locationManager:(CLLocationManager *)manager
didUpdateLocations:(NSArray *)locations
{
NSTimeInterval passedTime = -[self.lastUpdateTime timeIntervalSinceNow];
// Here we are checking how much seconds have passed since our lastUpdateTime
// Since lastUpdateTime is in the past, the result will be negative, therefore
// the minus sign, so we'll get a positive number
if(passedTime < 1) {
return;
} // Now we check if less than one second have passed. If so, the whole method
// will return. If not, it will just continue executing
CLLocation *currentLocation = [locations lastObject];
self.lastUpdateTime = [NSDate date]; // Don't forget to update the lastUpdateTime
// To hold the new update time
if (currentLocation != nil) {
NSLog(#"Location updated: %#", currentLocation);
_LatitudeLabel.text = [NSString stringWithFormat:#"%.8f", currentLocation.coordinate.latitude];
_LongitudeLabel.text = [NSString stringWithFormat:#"%.6f", currentLocation.coordinate.longitude];
_GPSAccuracyLabel.text = [NSString stringWithFormat:#"%.2f", currentLocation.horizontalAccuracy];
_AltitudeLabel.text = [NSString stringWithFormat:#"%.2f", currentLocation.altitude];
_VerticalAccuracyLabel.text = [NSString stringWithFormat:#"%.2f", currentLocation.verticalAccuracy];
}
}

Answer 2

#AMI289, your idea worked, no more double call.
I post the final code here in case it helps others, I just added back the locationManager = [[CLLocationManager alloc] init];.
// ViewController.m
#import "ViewController.h"
#interface ViewController ()
#property (nonatomic, strong) NSDate *lastUpdateTime; // create a property to hold current time.
#end
#implementation ViewController {
CLLocationManager *locationManager;
}
- (void)viewDidLoad {
[super viewDidLoad];
self.lastUpdateTime = [NSDate date]; // In viewDidLoad, 'initialize' it to get the current time
locationManager = [[CLLocationManager alloc] init];
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)getCurrentLocation:(id)sender {
locationManager.delegate = (id)self;
locationManager.desiredAccuracy = kCLLocationAccuracyBest;
[locationManager startUpdatingLocation];
}
#pragma mark - CLLocationManagerDelegate
- (void)locationManager:(CLLocationManager *)manager
didUpdateLocations:(NSArray *)locations
{
NSTimeInterval passedTime = -[self.lastUpdateTime timeIntervalSinceNow];
// Here we are checking how much seconds have passed since our lastUpdateTime
// Since lastUpdateTime is in the past, the result will be negative, therefore
// the minus sign, so we'll get a positive number
if(passedTime < 1) {
return;
} // Now we check if less than one second have passed. If so, the whole method
// will return. If not, it will just continue executing
CLLocation *currentLocation = [locations lastObject];
self.lastUpdateTime = [NSDate date]; // Don't forget to update the lastUpdateTime
// To hold the new update time
if (currentLocation != nil) {
NSLog(#"Location updated: %#", currentLocation);
_LatutideLabel.text = [NSString stringWithFormat:#"%.8f", currentLocation.coordinate.latitude];
_LongitudeLabel.text = [NSString stringWithFormat:#"%.6f", currentLocation.coordinate.longitude];
_GPSAccuracyLabel.text = [NSString stringWithFormat:#"%.2f", currentLocation.horizontalAccuracy];
_AltitudeLabel.text = [NSString stringWithFormat:#"%.2f", currentLocation.altitude];
_VerticalAccuracyLabel.text = [NSString stringWithFormat:#"%.2f", currentLocation.verticalAccuracy];
}
// Stop Location Manager
[locationManager stopUpdatingLocation];
}
#end