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I have an app that on startup centers on a specific location. 

//Calculate and set new center point
CLLocationCoordinate2D zoomLocation = CLLocationCoordinate2DMake(<some lat>,<some long>);

MKCoordinateSpan span;
span.latitudeDelta = 0.08;
span.longitudeDelta = 0.08;

//MKCoordinateRegion region = MKCoordinateRegionMake(zoomLocation, span);
MKCoordinateRegion region = [mapView regionThatFits:MKCoordinateRegionMake(zoomLocation, span)];

[mapView setRegion:region animated:YES];
[self refreshMap];

The call to refreshMap attempts to calculate the bounding box of the map so that I can query into the database for the respective information.

//Calculate map's bounding box
MKMapRect mapRect = [mapView visibleMapRect];

MKMapPoint cornerPointNE = MKMapPointMake(MKMapRectGetMaxX(mapRect), mapRect.origin.y);
CLLocationCoordinate2D upperLeft = MKCoordinateForMapPoint(cornerPointNE);

MKMapPoint cornerPointSW = MKMapPointMake(mapRect.origin.x, MKMapRectGetMaxY(mapRect));
CLLocationCoordinate2D lowerRight = MKCoordinateForMapPoint(cornerPointSW);

if( fabs(upperLeft.longitude) > 80.00 || fabs(lowerRight.longitude) > 80.0) {
    return;
}

The issue that I am seeing is that in iOS 6 the lowerRight coordinate is not correctly calculated at app startup and the map data does not get refreshed as the lowerRight.longitude is > 80.0. The upperLeft is correctly calculated.

After the app has finished loading if I pan the map even the slightest the bounding box calculations are correct.

This code works fine in iOS 5.

Is there a callback other than mapView:regionDidChangeAnimated that I could use? The rest of refreshMap is fairly intensive and I do not want to impact panning performance.

TIA

UPDATE

I seem to have found a fix. Instead of doing this

[mapView setRegion:region animated:YES];

I changed the YES to NO

[mapView setRegion:region animated:NO];

and now the lower corner is correctly calculated on app startup.

Timothy Reed
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    Curious why the code is checking if longitude is greater than 80 since the range for longitude is -180 to 180 (latitude must be from -90 to 90). –  Oct 28 '12 at 18:01
  • Its only checking for longitude greater than 80 in that I am only concerned about a certain state in the US that does not cross that line. This was a way to prevent the whole database from being queried and displayed from such a ridiculous altitude. – Timothy Reed Oct 29 '12 at 21:14

1 Answers1

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have you use MKMapRectOffset or Inset to move the visible rect slightly.

Also I keep re-reading your question and I may be wrong; but, I think the NE corner would be the upper right corner and the SW corner would be the lower left corner. Whereas you would want the NW and SE corners.

I have been unable to confirm in the Map Kit reference that the mapRect's origin is in the upper left corner.

Zaco
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