The map route display does not display correctly in the application

Question

I am implementing a map and it works well. But when I try to enlarge the map, I see this problem:

Here is my code:

- (MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id<MKOverlay>)overlay { MKPolylineRenderer *renderer = [[MKPolylineRenderer alloc] initWithPolyline:(id)overlay]; renderer.strokeColor = [UIColor redColor]; // pathColor; renderer.lineWidth = 7.0; return renderer; }