MapKit setRegion: not preserving span on iPhone

Question

I'm about to pull my hair out over this one. I am trying to restore the map the user was looking at when he last quit the app. When the app quits, I save the center location and the span of the current map. When the app launches again I read in these values and construct a MKCoordinateRegion and set the map's region to this. I've verified this region is correct. However, the map seems to have a mind of it's own. It often approximately doubles the span of the map. It never takes it exactly as I give it. Here is the code that sets the region:
mapView.delegate = self;
CLLocationCoordinate2D coordinate;
coordinate.latitude = settings.latitude;
coordinate.longitude = settings.longitude;
MKCoordinateSpan span;
span.latitudeDelta = settings.latitudeSpan;
span.longitudeDelta = settings.longitudeSpan;
MKCoordinateRegion region = MKCoordinateRegionMake(coordinate, span);
NSLog(@"initializing with latitudeSpan = %2.4f; longitudeSpan = %2.4f",
region.span.latitudeDelta, region.span.longitudeDelta);
[mapView setRegion:region animated:YES];
NSLog(@"after init, latitudeSpan = %2.4f; longitudeSpan = %2.4f",
mapView.region.span.latitudeDelta, mapView.region.span.longitudeDelta);
I can even set the maps's region to the exact same value it already has
[mapView setRegion:mapView.region];
and it still messes up. What's strange is that it doesn't seem consistent in what it is doing. Sometimes it exactly doubles the value and at other times it is some other fraction. I had thought this as just a 3.0 bug because it was working in 3.1. However, now I've found cases in 3.1 where it fails as well (but in different ways).
This is very strange. Has anyone else seen this (or not seen this)? Any solutions?
Message was edited by: btschumy
Message was edited by: btschumy

Answer 1

Hi BT,
I don't have any experience with Map Kit, but since no one else is responding I thought I might offer some of my general experience with bugs that don't appear to be deterministic.
Have you ruled out the possibility that you're applying the saved settings too early? You're setting the delegate in the same code block that restores the region, so it doesn't seem like you're waiting for mapViewDidFinishLoadingMap:. Have you tried restoring the same settings at a later time?
Even if you're sure the settings are being applied at the correct time, my instinct would be to apply them again, perhaps in the next event cycle. In fact I would go so far as to reset the frame and/or bounds of the content view at that time. View controllers have a mind of their own too, and they sometimes diddle with the frame of a content view before it appears. They only do this once however, so I've found a correction in a later event cycle fixes the problem.
Sorry if my lack of MK experience is all too clear, but I didn't want your post to go unnoticed, and a silly response has two benefits: 1) Your thread gets bumped; 2) An expert is more likely to join the thread if you provide a strawman to destroy.
\- Ray
p.s.: Hi Peter! For some reason I didn't see I was actually bumping your question, since BT probably solved the problem weeks ago. - R