How can I tell when regionChange event on MKMapView is programatic or user-drag of MKMapView?

Question

I have an MKMapView with a registered delegate so I can listen for region change events (specifically, regionDidChangeAnimated). I'm looking for a robust way of telling if a region change event was the result of a user dragging the map or from a programatic setRegion: request.

My goal is to have an app that auto-centers the map based on a location trace, unless the user has panned the map by hand, at which point auto-centering will turn off. Thus, I'm calling setRegion: to recenter the map view as appropriate, but I have a hard time telling if the resulting regionDidChangeAnimated: call to the delegate is programatic or from a user-pan. I've tried hacking something together, but I keep running into race conditions when the user starts panning just as a location update comes in.

Answer 1

I fixed this problem with a boolean that keeps track of code triggered region/center changes. Not the most elegant solution, but it works like a charm. It is a shame UIMapView does not derive from UIScrollView.

init:

regionChangeFromCode = FALSE;

button action:

-(IBAction) butCenterPressed:(id)sender
{   
    butCenter.selected = !butCenter.selected;       
    if(butCenter.selected)  
        [self setCenter];
}

set center:

-(void) setCenter
{
    regionChangeFromCode = TRUE; //before setCenterCoordinate, otherwise this is FALSE in regionWillChangeAnimated
    [theMap setCenterCoordinate:[self calcCenter]]; //this could also be [theMap setRegion]. Works the same
}

and the map delegate:

- (void)mapView:(MKMapView *)mapView regionWillChangeAnimated:(BOOL)animated
{
    if(!regionChangeFromCode) //so a user did it
    {
        if(butCenter.selected)
            butCenter.selected = FALSE;
    }
    regionChangeFromCode = FALSE;
}

In addition to this I have an update loop that updates the location and calls setCenter. When the button is selected the map center follows, and otherwise the center is left alone.