iOS 获取屏幕ZoomLevel值

#define MERCATOR_RADIUS85445659.44705395

- (int)getZoomLevel:(MKMapView*)_mapView {

    return 21-round(log2(_mapView.region.span.longitudeDelta * MERCATOR_RADIUS * M_PI / (180.0 * _mapView.bounds.size.width)));

}

- (void)mapView:(MKMapView*)_mapView regionDidChangeAnimated:(BOOL)animated {

    NSLog(@"zoom level %d", [selfgetZoomLevel:_mapView]);

}