Check whether zoom level changed

Question

I\'m using MapKit on iPhone. How can I know when the user changes the zoom level (zoom in\\out the map)?

I\'ve tried to use mapView:(MKMapView *)mapView regi

Answer 1

I have the following MKMapView category in which I include a method for quickly getting the current zoom level for the map:

@implementation MKMapView (ZoomLevel)

- (NSUInteger) zoomLevel {
    MKCoordinateRegion region = self.region;

    double centerPixelX = [MKMapView longitudeToPixelSpaceX: region.center.longitude];
    double topLeftPixelX = [MKMapView longitudeToPixelSpaceX: region.center.longitude - region.span.longitudeDelta / 2];

    double scaledMapWidth = (centerPixelX - topLeftPixelX) * 2;
    CGSize mapSizeInPixels = self.bounds.size;
    double zoomScale = scaledMapWidth / mapSizeInPixels.width;
    double zoomExponent = log(zoomScale) / log(2);
    double zoomLevel = 21 - zoomExponent;

    return zoomLevel;
}

@end

To obtain the zoom level, you can call the following in your delegates and determine if the zoom level has changed:

- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated {
    NSUInteger zoomLevel = [mapView zoomLevel];
}