CLLocationManager run loop

Question

I''m getting an infinite loop with the below code. When a user hits the "getDirections" method button, the alert fires correctly. When the choose "Get Drections" from alert buttons, google maps works perfectly. When they re-open the app, it opens back to this view and the app immediately goes back to google maps, rerunning the method again. THe only way I can stop this is to have the "Application does not run in background" turned to YES, which I don't want to do.

Can Someone tell my why this is happening?

-(IBAction)getDirections
{
    UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Directions" message:@"Do you want driving directions?" delegate:self cancelButtonTitle:@"No Thanks" otherButtonTitles:@"Get Directions", nil];
    [alert show];
    [alert release];
}

-(void)showDirections
{
    locationManager = [[CLLocationManager alloc] init];
    [locationManager setDesiredAccuracy:kCLLocationAccuracyNearestTenMeters];
    [locationManager setDelegate:self];

    [locationManager startUpdatingLocation];
}
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
    CLLocationCoordinate2D coord = [newLocation coordinate];
    NSArray *array = [dataHold objectForKey:@"Subtree"];
    NSString *latitude = [NSString stringWithFormat:@"%@",[array objectAtIndex:4]];
    NSString *longitude = [NSString stringWithFormat:@"%@",[array objectAtIndex:5]];
    double clubLatitude = [latitude doubleValue];
    double clubLongitude = [longitude doubleValue];
    urlString = [NSString stringWithFormat:@"http://maps.google.com/?saddr=%1.6f,%1.6f&daddr=%1.6f,%1.6f", coord.latitude, coord.longitude, clubLatitude, clubLongitude];
    [[UIApplication sharedApplication] openURL:[NSURL URLWithString:urlString]];
}

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
        buttonString = [alertView buttonTitleAtIndex:buttonIndex];
        if([buttonString isEqualToString:@"Get Directions"] )
        {
            [self showDirections];
            buttonString = nil;
        }
        else if( [buttonString isEqualToString:@"No Thanks"] )
        {
            nil;
        }
}

score 2 · Answer 1 · answered Sep 12 '11 at 21:35

The didUpdateToLocation delegate method is called constantly once you ccll CLLocationManager startUpdatingLocatoin.

Thus your code inside that didUpdateToLocation is called every time the location is updated - even when you launch the app back from the background. And the method is called a lot depending on the distanceFilter propery of your locationManager. You can confirm this by adding a NSLog statement to your delegate method and see how many times it is being called.

The Docs on that method:

Discussion Implementation of this method is optional. You should implement this method, however.

By the time this message is delivered to your delegate, the new location data is also available directly from the CLLocationManager object. The newLocation parameter may contain the data that was cached from a previous usage of the location service. You can use the timestamp property of the location object to determine how recent the location data is.

Follow that guide and save a timeStamp (or any other kind of identifier) inside the didUpdateToLocation method.

Once you have set the timeStamp, you can display the google maps using those values. Sidenote: Your CLLocationManager has a property location that gets updates every time the didUpdateToLocation is called - thus you can rely on that property to get the current location elsewhere in your code.

HTH

Shaharyar, since I only needed one didUpdateToLocation, I called stopUpdatingLocation at the end of the didUpdateToLocation method. Worked great. Thanks so much! — Eric, Sep 12 '11 at 21:40

score 2 · Accepted Answer · answered Sep 12 '11 at 21:36

You are missing the following piece of code. You should add it to the (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation method

[locationManager stopUpdatingLocation];

CLLocationManager run loop

2 Answers2