iOS: mapview and center one marker

Question

I have this code where in iOS6 I center a marker in the center in a mapview, it don't happen in iOS 7 why?

- (void)mapView:(MKMapView *)mapView didAddAnnotationViews:(NSArray *)views {

    MKMapRect zoomRect = MKMapRectNull;
    for (id <MKAnnotation> annotation in mapView.annotations)
    {
        MKMapPoint annotationP = MKMapPointForCoordinate(annotation.coordinate);
        MKMapRect pointRect = MKMapRectMake(annotationP.x, annotationP.y, 7000, 7000);
        if (MKMapRectIsNull(zoomRect)) {
            zoomRect = pointRect;
        } else {
            zoomRect = MKMapRectUnion(zoomRect, pointRect);
        }
    }

    [mapView setVisibleMapRect:zoomRect animated:YES];

}