Why the MKPolyline didn't show up in my application? - swift

Question

I am trying to create an application, one of its function is to drawing the line while users are moving.
Here is the class
class traceuserViewController: UIViewController,CLLocationManagerDelegate, MKMapViewDelegate {
var locationManager = CLLocationManager()
var startLocation: CLLocation?
var endLocation: CLLocation?
#IBOutlet weak var mapView: MKMapView!
override func viewDidLoad() {
super.viewDidLoad()
locationManager.delegate = self
self.locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters
self.locationManager.distanceFilter = 30.0
self.locationManager.startMonitoringSignificantLocationChanges()
self.locationManager.startUpdatingLocation()
mapView.showsUserLocation = true
mapView.mapType = .hybrid
self.mapView.delegate = self
}
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
//user's current location
let nowlocation = locations.last
userLocations.append(nowlocation!)
print("HERE IS THE LOCATION ARRAY")
print(userLocations)
//show the current location region
let center = CLLocationCoordinate2D(latitude: nowlocation!.coordinate.latitude, longitude: nowlocation!.coordinate.longitude)
let region = MKCoordinateRegion(center: center, span: MKCoordinateSpan(latitudeDelta: 0.7, longitudeDelta: 0.7))
self.mapView.setRegion(region, animated: true)
drawRoute(locationArray: userLocations)
}
func drawRoute(locationArray: [CLLocation]) {
if (locationArray.count) > 1 {
var destinationLocIndex = (locationArray.count) - 1
var startLocIndex = (locationArray.count) - 2
let destinationloc = locationArray[destinationLocIndex].coordinate
let startLoc = locationArray[startLocIndex].coordinate
var routeArray = [startLoc, destinationloc]
//test if the function works well or not
print(routeArray)
var geodesicLine = MKGeodesicPolyline(coordinates: routeArray , count: routeArray.count)
mapView.add(geodesicLine, level: .aboveRoads)
}
}
//draw in the mapview
private func mapView(mapView: MKMapView, rendererForOverlay overlay: MKOverlay) -> MKOverlayRenderer! {
if overlay is MKPolyline{
let polylineRenderer = MKPolylineRenderer(overlay: overlay)
polylineRenderer.strokeColor = UIColor.blue
polylineRenderer.lineWidth = 5.0
return polylineRenderer
}else{
os_log("Failed to draw the polyline", log: OSLog.default, type: .debug)
return nil
}
}
After many times trying, I still have no idea why it doesn't draw the route on the map when the user is moving, can anyone please I've me some hints?
cheers

Answer 1

I'm inferring that you are using Swift 3 from the code snippet (e.g. the signature of didUpdateLocations; the use of .hybrid rather than Swift 2.3's .Hybrid; etc.).
But, the signature for mapView(_:rendererFor:) is incorrect. In Swift 3, it is:
func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
...
}
If you ever have a delegate method that doesn't appear to work, add a breakpoint in it and you can confirm if it's called at all or not (and if it is called, you can step through it and diagnose the problem further).