CODEWITHSUNDEEP
iphonelocationmkmapviewzooming
DJHoward
DJHoward

Reputation: 111

Preventing MKMapView from continually re-zooming and re-centering to user location

I seem to have the opposite problem from many of those posted here about MKMapView. Rather than not being able to get it to zoom to and display the current location, I can't seem to get it to stop doing so. Here's what happens:

I've tried telling my CLLocationManager to stopUpdatingLocation (no effect, since an MKMapView knows how to use CoreLocation), and I've tried telling the MKMapView to setShowsUserLocation:NO (no blue dot displayed at all, which is not what I want). I even tried eliminating my CLLocationManager (no effect). What is causing this and how do I stop it?

Yes, I do set the location manager's accuracy and distance in -loadView.

I don't implement -mapViewDidFinishLoadingMap:. Here is my implementation of 

-locationManager:didUpdateToLocation:fromLocation:
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
    // How many seconds ago was this new location created?
    NSTimeInterval t = [[newLocation timestamp] timeIntervalSinceNow];

    // CLLocationManagers will return the last found location of the device first,
    // you don't want that data in this case. If this location was made more than 3
    // minutes ago, ignore it.
    if (t < -180)
    {
        // This is cached data, you don't want it, keep looking
        return;
    }

    [locationManager stopUpdatingLocation];
}

I think this is the centering you're asking about, @Anna Karenina:

- (void)mapView:(MKMapView *)mv didUpdateUserLocation:(MKUserLocation *)u
{
    CLLocationCoordinate2D loc = [u coordinate];
    // Display the region 500 meters square around the current location
    MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(loc, 500, 500);
    [mv setRegion:region animated:YES];
}

Upvotes: 11

Views: 4374

Answers (3)

Sukwon
Sukwon

Reputation: 239

I use dispatch_once in MKMapViewDelegate method to zoom only once at the beginning. Here is the code.

- (void)mapView:(MKMapView *)mapView didUpdateUserLocation:(MKUserLocation *)userLocation  {    
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        CLLocationCoordinate2D newCoordinate = CLLocationCoordinate2DMake(mapView.userLocation.coordinate.latitude, mapView.userLocation.coordinate.longitude);

        MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(newCoordinate, 500, 500);
        [mapView setRegion:region animated:YES];
    });
}

Upvotes: 0

tasnim ahmed
tasnim ahmed

Reputation: 41

Dont implement - (void)mapView:(MKMapView *)mv didUpdateUserLocation:(MKUserLocation *)u method.

Instead use locationmanager didUpdateToLocation.

didUpdateUserLocation is called multiple times without any reason.where didUpdateToLocation is called when any location changes occurred.

Then u can manually set the mkmapview region in the didUpdateToLocation method.

Upvotes: 4

chown
chown

Reputation: 52798

First, and I dont know that this will effect things much, but do you set your location managers accuracy and distance filter at all in viewDidLoad (or wherever you are implementing your locationManager):

[locationManager setDesiredAccuracy:kCLLocationAccuracyBest];
[locationManager setDistanceFilter:kCLDistanceFilterNone];

Second, check these 2 functions in your source (ignore the content of the actual functions I have listed here, it is just for illustration and to show usage) and if possible, provide your code for these functions so we can better assist:

- (void)mapViewDidFinishLoadingMap:(MKMapView *)mapView
{
    [activityIndicator stopAnimating];
}

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
    NSDate* eventDate = newLocation.timestamp;
    NSTimeInterval howRecent = [eventDate timeIntervalSinceNow];
    if (abs(howRecent) < 15.0)
    {
        NSLog(@"New Latitude %+.6f, Longitude %+.6f", newLocation.coordinate.latitude, newLocation.coordinate.longitude);
    }
}

Upvotes: 0

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