MKCoordinateregion's center changes when span changed - iphone

Question

I have a MKCoordinateregion called region. I want to change span of this region without changing it's center. I am using following method to change zoom.

 -(void) changeZoom
    {

     NSLog(@"before zoom span, center are   %f, %f,%f,%f", region.span.latitudeDelta, region.span.longitudeDelta, mymap.centerCoordinate.latitude, mymap.centerCoordinate.longitude);
                region.span.latitudeDelta = current_factor ;
                region.span.longitudeDelta = current_factor ;
                region.center.latitude = mymap.centerCoordinate.latitude ;
                region.center.longitude = mymap.centerCoordinate.longitude ;
                [mymap setRegion:region animated:TRUE];

                NSLog(@"after zoom span, center are   %f, %f,%f,%f", region.span.latitudeDelta, region.span.longitudeDelta, mymap.centerCoordinate.latitude, mymap.centerCoordinate.longitude);
    }

Log shows :

before zoom span, center are   0.021950, 0.021950,19.068080,72.838111
 after zoom span, center are   0.043901, 0.043901,19.068040,72.838154

This method set's span accurately as desired.But I dont want any change in the center's coordinate, Because when I zoom out and then zoom back I end up at a location different from starting location.

Is there any method so that zoom in and out are possible without any change in center?

Thanks for any help in advance.

nevan king nevan king · Accepted Answer · 2011-10-01T12:59:56

Your before and after center coordinates are almost exactly the same, so it shouldn't be a problem. If you really want the exact same center coordinates, call setCenterCoordinate:animated: right after you use setRegion:animated: and pass some saved center coordinates.

CLLocationCoordinate2D originalCenter = mymap.centerCoordinate;
// ... adjust region
[mymap setCenterCoordinate:originalCenter animated:NO];

Also, you should use YES instead of TRUE for booleans:

[mymap setRegion:region animated:YES];

MKCoordinateregion's center changes when span changed - iphone

2 Answers