Draw polyline using Swift

TJ Rogers picture TJ Rogers · Dec 19, 2014 · Viewed 22.1k times · Source

I'm trying to get an understanding of how to draw polylines using Swift. I've looked at the documentation, referenced some tutorials, and checked out some other SO posts, but I still can't get the thing to draw a line on my map. Here's my code. Anyone tell me what I'm doing wrong here?

import UIKit
import MapKit

class FirstViewController: UIViewController {

    @IBOutlet weak var map: MKMapView!

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)

        let location = CLLocationCoordinate2D(
            latitude: -73.761105,
            longitude: 41.017791
        )

        let span = MKCoordinateSpanMake(0.07, 0.07)
        let region = MKCoordinateRegion(center: location, span: span)
        map.setRegion(region, animated: true)

        let annotation = MKPointAnnotation()
        annotation.setCoordinate(location)
        annotation.title = "White Plains"
        annotation.subtitle = "Westchester County"
        map.addAnnotation(annotation)

        var locations = [CLLocation(latitude: -73.761105, longitude: 41.017791), CLLocation(latitude: -73.760701,longitude: 41.019348), CLLocation(latitude: -73.757201, longitude: 41.019267), CLLocation(latitude: -73.757482, longitude: 41.016375), CLLocation(latitude: -73.761105, longitude: 41.017791)]
        var coordinates = locations.map({(location: CLLocation!) -> CLLocationCoordinate2D in return location.coordinate})
        var polyline = MKPolyline(coordinates: &coordinates, count: locations.count)

        self.map.addOverlay(polyline)

    }

    func mapView(mapView: MKMapView!, rendererForOverlay overlay: MKOverlay!) -> MKOverlayRenderer! {
        if overlay is MKPolyline {
            var polylineRenderer = MKPolylineRenderer(overlay: overlay)
            polylineRenderer.strokeColor = UIColor.blueColor()
            polylineRenderer.lineWidth = 5
            return polylineRenderer
        }

        return nil
    }

}

Thanks!

Answer

Kampai picture Kampai · Dec 19, 2014

Here MKGeodesicPolyline will solve your problem. Add object of MKGeodesicPolyline instead of MKPolyline.

In your code remove below two lines:

    let polyline = MKPolyline(coordinates: &coordinates, count: locations.count)
    map.add(polyline)

And add these lines:

    let geodesic = MKGeodesicPolyline(coordinates: coordinates, count: 2)
    map.addOverlay(geodesic)

Swift 5.0:

func createPolyline(mapView: MKMapView) {
    let point1 = CLLocationCoordinate2DMake(-73.761105, 41.017791);
    let point2 = CLLocationCoordinate2DMake(-73.760701, 41.019348);
    let point3 = CLLocationCoordinate2DMake(-73.757201, 41.019267);
    let point4 = CLLocationCoordinate2DMake(-73.757482, 41.016375);
    let point5 = CLLocationCoordinate2DMake(-73.761105, 41.017791);
    
    let points: [CLLocationCoordinate2D]
    points = [point1, point2, point3, point4, point5]
    
    let geodesic = MKGeodesicPolyline(coordinates: points, count: 5)
    map.addOverlay(geodesic)
    
    UIView.animate(withDuration: 1.5, animations: { () -> Void in
        let span = MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01)
        let region1 = MKCoordinateRegion(center: point1, span: span)
        self.map.setRegion(region1, animated: true)
    })
}

Objective C code:

- (void) createGeoPolyline {
    
    CLLocationCoordinate2D point1 = { -73.761105, 41.017791 };
    CLLocationCoordinate2D point2 = { -73.760701, 41.019348 };
    CLLocationCoordinate2D point3 = { -73.757201, 41.019267 };
    CLLocationCoordinate2D point4 = { -73.757482, 41.016375 };
    CLLocationCoordinate2D point5 = { -73.761105, 41.017791 };

   CLLocationCoordinate2D points[] = {point1, point2, point3, point4, point5};
    
    MKGeodesicPolyline *geodesic = [MKGeodesicPolyline polylineWithCoordinates:&points[0] count:5];
    [self.mapView addOverlay:geodesic];
    
    [UIView animateWithDuration:1.5 animations:^{
        MKCoordinateRegion region;
        region.center = point1;
        
        MKCoordinateSpan span;
        span.latitudeDelta  = 0.01;
        span.longitudeDelta = 0.01;
        region.span = span;
        [self.mapView setRegion:region animated:YES];
    }];
}

Above Objective C code works perfect and it will show overlay below:

enter image description here

But if you try Swift code it will not. I tried as much as I can to solve it out but It won't change. May be it is bug from MapKit framework.