Xamarin Forms Custom Map renderer to draw Polylines

App.cs

using System;
using Xamarin.Forms;
using Xamarin.Forms.Maps;

namespace YourNameSpace
{
	public class App : Application
    {
		public App()
		{
			MainPage = new MapPage();
		}
    }

	public class MapPage : ContentPage {
		public MapPage() {
			var map = new MyMap(
				MapSpan.FromCenterAndRadius(
					new Position(37,-122), Distance.FromMiles(0.3))) {
				IsShowingUser = true, // iOS asks for permission if this is set to true, but not if not set or set to false.
				HeightRequest = 100,
				WidthRequest = 960,
				VerticalOptions = LayoutOptions.FillAndExpand
			};
			var stack = new StackLayout { Spacing = 0 };
			stack.Children.Add(map);
			Content = stack;
		}
	}

	public class MyMap : Map {

		public MyMap(MapSpan region) : base(region)
		{
		}
	}
}

MyMaprednereriOS.cs

using System;
using Xamarin.Forms;
using YourNameSpace;
using YourNameSpace.iOS;
using Xamarin.Forms.Maps.iOS;
using MapKit;
using UIKit;
using CoreLocation;



[assembly: ExportRenderer (typeof (MyMap), typeof (MyMapRenderer))]
namespace YourNameSpace.iOS
{
    public class MyMapRenderer : MapRenderer
    {
		MKMapView mapView;
		MyMap myMap;
		MKPolyline lineOverlay;
		MKPolylineRenderer lineRenderer;

		protected override void OnElementChanged(Xamarin.Forms.Platform.iOS.ElementChangedEventArgs<View> e)
		{
			base.OnElementChanged(e);

			if (e.OldElement == null) {

				mapView = Control as MKMapView;

				myMap = e.NewElement as MyMap;

				mapView.OverlayRenderer = (m, o) => {
					if(lineRenderer == null) {
						lineRenderer = new MKPolylineRenderer(o as MKPolyline);
						lineRenderer.StrokeColor = UIColor.Red;
						lineRenderer.FillColor = UIColor.Red;
					}
					return lineRenderer;
				};
				
				var point1 = new CLLocationCoordinate2D(37,-122);
				var point2 = new CLLocationCoordinate2D(37,-122.001);
				var point3 = new CLLocationCoordinate2D(37.001,-122.002);
				
				lineOverlay = MKPolyline.FromCoordinates(new CLLocationCoordinate2D[] {point1, point2, point3});
				mapView.AddOverlay (lineOverlay);
			}
		}
    }
}

MyMapRendererAndroid.cs

using System;
using Xamarin.Forms;
using YourNameSpace;
using YourNameSpace.Android;
using Xamarin.Forms.Maps.Android;
using Android.Gms.Maps;
using Android.Gms.Maps.Model;


[assembly: ExportRenderer (typeof (MyMap), typeof (MyMapRenderer))]
namespace YourNameSpace.Android
{
    public class MyMapRenderer : MapRenderer
    {
		MapView mapView;
		GoogleMap map;
		MyMap myMap;

		protected override void OnElementChanged(Xamarin.Forms.Platform.Android.ElementChangedEventArgs<Xamarin.Forms.View> e)
		{
			base.OnElementChanged(e);

			if (e.OldElement == null) {

				mapView = Control as MapView;
				map = mapView.Map;

				myMap = e.NewElement as MyMap;

				PolylineOptions line = new PolylineOptions();
				line.InvokeColor(global::Android.Graphics.Color.Red);
				// Add the points of the polyline
				LatLng latLng = new LatLng(37,-122);
				line.Add(latLng);
				latLng = new LatLng(37,-122.001);
				line.Add(latLng);
				latLng = new LatLng(37.001,-122.002);
				line.Add(latLng);
				// Add the polyline to the map
				map.AddPolyline(line);

			}
		}
    }
}

myMap = e.NewElement as MyMap; is never used.

Hello,
Your example really helps.
Can you explain me how can i modify this code to add a polyline when maps was already created and also an event (marker clicked) ?

Thank you.