我的代码-(IBAction)zoomOut:(id)sender{
MKCoordinateRegion theRegion=mapView.region;
theRegion.span.longitudeDelta*=2.0;
theRegion.span.latitudeDelta*=2.0;
[mapView setRegion:theRegion animated:YES];
}
当缩小到最后一级时,程序就会自动退出.请问这是怎么回事