How do I zoom an MKMapView to the users current location without CLLocationManager?

Question

With the MKMapView there's an option called "Show users current location" which will automatically show a users location on the map.

I'd like to move and zoom to this location when it's found (and if it changes).

The problem is, there doesn't appear to be any method called when the user location is updated on the map, so I have nowhere to put the code that will zoom/scroll.

Is there a way to be notified when an MKMapView has got (or updated) the user location so I can move/zoom to it? If I use my own CLLocationManager the updates I get do not correspond with the updates of the user marker on the map, so it looks silly when my map moves and zooms seconds before the blue pin appears.

This feels like basic functionality, but I've spent weeks looking for a solution and not turned up anything close.

Answer 1

No problem... Inside the viewDidLoad method of your UIViewController subclass that has the MKMapView add this (assuming your MKMapView is named map):

CLLocation *location = [[[CLLocation alloc] initWithLatitude:map.centerCoordinate.latitude longitude:map.centerCoordinate.longitude] autorelease]; //Get your location and create a CLLocation
MKCoordinateRegion region; //create a region.  No this is not a pointer
region.center = location.coordinate;  // set the region center to your current location
MKCoordinateSpan span; // create a range of your view
span.latitudeDelta = BASE_RADIUS / 3;  // span dimensions.  I have BASE_RADIUS defined as 0.0144927536 which is equivalent to 1 mile
span.longitudeDelta = BASE_RADIUS / 3;  // span dimensions
region.span = span; // Set the region's span to the new span.
[map setRegion:region animated:YES]; // to set the map to the newly created region

Answer 2

Copy the code in the viewWillAppear method.

Answer 3

You have to register for KVO notifications of userLocation.location property of MKMapView.

To do this, put this code in viewDidLoad: of your ViewController or anywhere in the place where your map view is initialized.

[self.mapView.userLocation addObserver:self  
        forKeyPath:@"location"  
           options:(NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld)  
           context:NULL];

Then implement this method to receive KVO notifications

-(void)observeValueForKeyPath:(NSString *)keyPath  
                     ofObject:(id)object  
                       change:(NSDictionary *)change  
                      context:(void *)context {  

    if ([self.mapView isUserLocationVisible]) {  
        [self moveOrZoomOrAnythingElse];
        // and of course you can use here old and new location values
    }
}

This code works fine for me.
BTW, self is my ViewController in this context.