iOS 5中无效的MKMapView区域

Question

MKMapView returns an invalid region under iOS 5 -- latitude + latitudeDelta/2 is over 100 and shouldn't be over 90.

Has anyone seen this problem?

Steps to Reproduce:

1. Create an MKMapView
2. Log the mapView.region from within the regionDidChangeAnimated delegate method
3. Zoom out the map as far as possible and drag it to the right, so the view is scrolled to the top/left

Expected Results: In iOS 4, the mapView.region is reasonable:

lat=2.202047 lon=-67.500000 latDelta=165.698164 lonDelta=225.000000

In iOS 5, however, the mapView.region is out of bounds:

lat=17.978733 lon=-67.500000 latDelta=165.698164 lonDelta=225.000000

Latitudes should be within the -90 to 90 range. However, in iOS 5, lat + latDelta/2 is 100.827815. That is not possible. While I can clamp the values at +/- 90, the offset difference is causing problems with our overlays.

Regression: Does not happen in iOS 4.3. Happens regularly in iOS 5. Screen dumps of the map views look identical even though the center latitude is 15 degrees off.

Notes: Project file and screen dumps can be downloaded here .

Answer 1

This seems to be an adequate workaround. Rather than reading the mapView.region property, call this method instead:

@implementation MKMapView(fixedRegion)

-(MKCoordinateRegion) fixedRegion_
{
  // this call is broken on iOS 5, as is the region property, so don't use them
  // return( [self convertRect:self.bounds toRegionFromView:self] );

  CLLocationCoordinate2D topLeft = [self convertPoint:CGPointZero toCoordinateFromView:self];
  CLLocationCoordinate2D bottomRight = [self convertPoint:CGPointMake(self.bounds.size.width, self.bounds.size.height) toCoordinateFromView:self];

  MKCoordinateRegion region;
  region.center.latitude = (topLeft.latitude + bottomRight.latitude)/2;
  region.center.longitude = (topLeft.longitude + bottomRight.longitude)/2; 
  region.span.latitudeDelta = fabs( topLeft.latitude - bottomRight.latitude );
  region.span.longitudeDelta = fabs( topLeft.longitude - bottomRight.longitude );
  return region;
}
@end

Now one could argue (correctly!) that this code isn't 100% correct either because the center value of a Mercator projection in lon/lat isn't really halfway between the top and bottom, but since this matches iOS 4 functionality and keeps the values within the legal range for the map, it works for me.

Answer 2

By using the MKMapView+ZoomLevel category, you won't have to bother setting the region at all.

here is very good tutorial on the same

http://troybrant.net/blog/2010/01/set-the-zoom-level-of-an-mkmapview/

or

http://mayurbirari.wordpress.com/2011/02/07/how-to-access-mkmapkit-in-iphone/

After you perform the zoom/pinch operation try to load the region in

      -(void) mapView:(MKMapView *)mapView regionWillChangeAnimated:(BOOL)animated

instead in

        regionDidChangeAnimated.

hope this will help..:)