MapRenderer.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Linq;
using System.Threading.Tasks;
using Windows.Devices.Geolocation;
using Windows.UI;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls.Maps;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Shapes;
using Xamarin.Forms.Platform.UWP;

namespace Xamarin.Forms.Maps.UWP
{
	public class MapRenderer : ViewRenderer<Map, MapControl>
	{
		protected override async void OnElementChanged(ElementChangedEventArgs<Map> e)
		{
			base.OnElementChanged(e);

			if (e.OldElement != null)
			{
				var mapModel = e.OldElement;
				MessagingCenter.Unsubscribe<Map, MapSpan>(this, "MapMoveToRegion");
				((ObservableCollection<Pin>)mapModel.Pins).CollectionChanged -= OnPinCollectionChanged;
				((ObservableCollection<MapElement>)mapModel.MapElements).CollectionChanged -= OnMapElementCollectionChanged;
			}

			if (e.NewElement != null)
			{
				var mapModel = e.NewElement;

				if (Control == null)
				{
					SetNativeControl(new MapControl());
					Control.MapServiceToken = FormsMaps.AuthenticationToken;
					Control.ZoomLevelChanged += async (s, a) => await UpdateVisibleRegion();
					Control.CenterChanged += async (s, a) => await UpdateVisibleRegion();
					Control.MapTapped += OnMapTapped;
					Control.LayoutUpdated += OnLayoutUpdated;
				}

				MessagingCenter.Subscribe<Map, MapSpan>(this, "MapMoveToRegion", async (s, a) => await MoveToRegion(a), mapModel);

				UpdateMapType();
				UpdateHasScrollEnabled();
				UpdateHasZoomEnabled();

				((ObservableCollection<Pin>)mapModel.Pins).CollectionChanged += OnPinCollectionChanged;
				if (mapModel.Pins.Any())
					LoadPins();

				((ObservableCollection<MapElement>)mapModel.MapElements).CollectionChanged += OnMapElementCollectionChanged;
				if (mapModel.MapElements.Any())
					LoadMapElements(mapModel.MapElements);

				if (Control == null)
					return;

				await Control.Dispatcher.RunIdleAsync(async (i) => await MoveToRegion(mapModel.LastMoveToRegion, MapAnimationKind.None));
				await UpdateIsShowingUser();
			}
		}

		bool _isRegionUpdatePending;

		async void OnLayoutUpdated(object sender, object e)
		{
			if (_isRegionUpdatePending)
			{
				// _isRegionUpdatePending is set to false when the update is successfull
				await MoveToRegion(Element.LastMoveToRegion, MapAnimationKind.None);
			}
		}

		protected override async void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
		{
			base.OnElementPropertyChanged(sender, e);

			if (e.PropertyName == Map.MapTypeProperty.PropertyName)
				UpdateMapType();
			else if (e.PropertyName == Map.IsShowingUserProperty.PropertyName)
				await UpdateIsShowingUser();
			else if (e.PropertyName == Map.HasScrollEnabledProperty.PropertyName)
				UpdateHasScrollEnabled();
			else if (e.PropertyName == Map.HasZoomEnabledProperty.PropertyName)
				UpdateHasZoomEnabled();
		}

		protected override void Dispose(bool disposing)
		{
			if (disposing && !_disposed)
			{
				_disposed = true;

				_timer?.Stop();
				_timer = null;

				MessagingCenter.Unsubscribe<Map, MapSpan>(this, "MapMoveToRegion");

				if (Element != null)
				{
					((ObservableCollection<Pin>)Element.Pins).CollectionChanged -= OnPinCollectionChanged;
					((ObservableCollection<MapElement>)Element.MapElements).CollectionChanged -= OnMapElementCollectionChanged;
				}

				if (Control != null)
				{
					Control.LayoutUpdated -= OnLayoutUpdated;
					Control.MapTapped -= OnMapTapped;
				}
			}

			base.Dispose(disposing);
		}

		bool _disposed;
		Ellipse _userPositionCircle;
		DispatcherTimer _timer;

		void OnPinCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
		{
			if (Device.IsInvokeRequired)
			{
				Device.BeginInvokeOnMainThread(() => PinCollectionChanged(e));
			}
			else
			{
				PinCollectionChanged(e);
			}
		}

		void PinCollectionChanged(NotifyCollectionChangedEventArgs e)
		{
			switch (e.Action)
			{
				case NotifyCollectionChangedAction.Add:
					foreach (Pin pin in e.NewItems)
						LoadPin(pin);
					break;
				case NotifyCollectionChangedAction.Move:
					// no matter
					break;
				case NotifyCollectionChangedAction.Remove:
					foreach (Pin pin in e.OldItems)
						RemovePin(pin);
					break;
				case NotifyCollectionChangedAction.Replace:
					foreach (Pin pin in e.OldItems)
						RemovePin(pin);
					foreach (Pin pin in e.NewItems)
						LoadPin(pin);
					break;
				case NotifyCollectionChangedAction.Reset:
					ClearPins();
					LoadPins();
					break;
			}
		}

		void LoadPins()
		{
			foreach (var pin in Element.Pins)
				LoadPin(pin);
		}

		void ClearPins()
		{
			Control.Children.Clear();
#pragma warning disable 4014 // don't wanna block UI thread
			UpdateIsShowingUser();
#pragma warning restore
		}

		void RemovePin(Pin pinToRemove)
		{
			var pushPin = Control.Children.FirstOrDefault(c =>
			{
				var pin = (c as PushPin);
				return (pin != null && pin.DataContext.Equals(pinToRemove));
			});

			if (pushPin != null)
				Control.Children.Remove(pushPin);
		}

		void LoadPin(Pin pin)
		{
			Control.Children.Add(new PushPin(pin));
		}

		void OnMapElementCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
		{
			if (Device.IsInvokeRequired)
			{
				Device.BeginInvokeOnMainThread(() => MapElementCollectionChanged(e));
			}
			else
			{
				MapElementCollectionChanged(e);
			}
		}

		void MapElementCollectionChanged(NotifyCollectionChangedEventArgs e)
		{
			switch (e.Action)
			{
				case NotifyCollectionChangedAction.Add:
					LoadMapElements(e.NewItems.Cast<MapElement>());
					break;
				case NotifyCollectionChangedAction.Remove:
					RemoveMapElements(e.OldItems.Cast<MapElement>());
					break;
				case NotifyCollectionChangedAction.Replace:
					RemoveMapElements(e.OldItems.Cast<MapElement>());
					LoadMapElements(e.NewItems.Cast<MapElement>());
					break;
				case NotifyCollectionChangedAction.Reset:
					Control.MapElements.Clear();
					LoadMapElements(Element.MapElements);
					break;
			}
		}

		void LoadMapElements(IEnumerable<MapElement> mapElements)
		{
			foreach (var formsMapElement in mapElements)
			{
				Windows.UI.Xaml.Controls.Maps.MapElement nativeMapElement = null;

				switch (formsMapElement)
				{
					case Polyline polyline:
						nativeMapElement = LoadPolyline(polyline);
						break;
					case Polygon polygon:
						nativeMapElement = LoadPolygon(polygon);
						break;
					case Circle circle:
						nativeMapElement = LoadCircle(circle);
						break;
				}

				Control.MapElements.Add(nativeMapElement);

				formsMapElement.PropertyChanged += MapElementPropertyChanged;
				formsMapElement.MapElementId = nativeMapElement;
			}
		}

		void RemoveMapElements(IEnumerable<MapElement> mapElements)
		{
			foreach (var mapElement in mapElements)
			{
				mapElement.PropertyChanged -= MapElementPropertyChanged;
				Control.MapElements.Remove((Windows.UI.Xaml.Controls.Maps.MapElement)mapElement.MapElementId);
			}
		}

		void MapElementPropertyChanged(object sender, PropertyChangedEventArgs e)
		{
			switch (sender)
			{
				case Polyline polyline:
					OnPolylinePropertyChanged(polyline, e);
					break;
				case Polygon polygon:
					OnPolygonPropertyChanged(polygon, e);
					break;
				case Circle circle:
					OnCirclePropertyChanged(circle, e);
					break;
			}
		}

		protected Geopath PositionsToGeopath(IList<Position> positions)
		{
			// Geopath constructor throws an exception on an empty list
			if (positions.Any())
			{
				return new Geopath(positions.Select(p => new BasicGeoposition
				{
					Latitude = p.Latitude,
					Longitude = p.Longitude
				}));
			}
			else
			{
				return new Geopath(new[]
				{
					new BasicGeoposition(),
				});
			}
		}

		#region Polylines

		protected virtual MapPolyline LoadPolyline(Polyline polyline)
		{
			return new MapPolyline()
			{
				Path = PositionsToGeopath(polyline.Geopath),
				StrokeColor = polyline.StrokeColor.IsDefault ? Colors.Black : polyline.StrokeColor.ToWindowsColor(),
				StrokeThickness = polyline.StrokeWidth
			};
		}

		void OnPolylinePropertyChanged(Polyline polyline, PropertyChangedEventArgs e)
		{
			var mapPolyline = (MapPolyline)polyline.MapElementId;

			if (mapPolyline == null)
			{
				return;
			}

			if (e.PropertyName == Polyline.StrokeColorProperty.PropertyName)
			{
				mapPolyline.StrokeColor = polyline.StrokeColor.IsDefault ? Colors.Black : polyline.StrokeColor.ToWindowsColor();
			}
			else if (e.PropertyName == Polyline.StrokeWidthProperty.PropertyName)
			{
				mapPolyline.StrokeThickness = polyline.StrokeWidth;
			}
			else if (e.PropertyName == nameof(Polyline.Geopath))
			{
				mapPolyline.Path = PositionsToGeopath(polyline.Geopath);
			}
		}

		#endregion

		#region Polygons

		protected virtual MapPolygon LoadPolygon(Polygon polygon)
		{
			return new MapPolygon()
			{
				Path = PositionsToGeopath(polygon.Geopath),
				StrokeColor = polygon.StrokeColor.IsDefault ? Colors.Black : polygon.StrokeColor.ToWindowsColor(),
				StrokeThickness = polygon.StrokeWidth,
				FillColor = polygon.FillColor.ToWindowsColor()
			};
		}

		void OnPolygonPropertyChanged(Polygon polygon, PropertyChangedEventArgs e)
		{
			var mapPolygon = (MapPolygon)polygon.MapElementId;

			if (mapPolygon == null)
			{
				return;
			}

			if (e.PropertyName == MapElement.StrokeColorProperty.PropertyName)
			{
				mapPolygon.StrokeColor = polygon.StrokeColor.IsDefault ? Colors.Black : polygon.StrokeColor.ToWindowsColor();
			}
			else if (e.PropertyName == MapElement.StrokeWidthProperty.PropertyName)
			{
				mapPolygon.StrokeThickness = polygon.StrokeWidth;
			}
			else if (e.PropertyName == Polygon.FillColorProperty.PropertyName)
			{
				mapPolygon.FillColor = polygon.FillColor.ToWindowsColor();
			}
			else if (e.PropertyName == nameof(Polygon.Geopath))
			{
				mapPolygon.Path = PositionsToGeopath(polygon.Geopath);
			}
		}

		#endregion

		#region Circles

		protected virtual MapPolygon LoadCircle(Circle circle)
		{
			return new MapPolygon()
			{
				Path = PositionsToGeopath(circle.ToCircumferencePositions()),
				StrokeColor = circle.StrokeColor.IsDefault ? Colors.Black : circle.StrokeColor.ToWindowsColor(),
				StrokeThickness = circle.StrokeWidth,
				FillColor = circle.FillColor.ToWindowsColor()
			};
		}

		void OnCirclePropertyChanged(Circle circle, PropertyChangedEventArgs e)
		{
			var mapPolygon = (MapPolygon)circle.MapElementId;

			if (mapPolygon == null)
			{
				return;
			}

			if (e.PropertyName == MapElement.StrokeColorProperty.PropertyName)
			{
				mapPolygon.StrokeColor = circle.StrokeColor.IsDefault ? Colors.Black : circle.StrokeColor.ToWindowsColor();
			}
			else if (e.PropertyName == MapElement.StrokeWidthProperty.PropertyName)
			{
				mapPolygon.StrokeThickness = circle.StrokeWidth;
			}
			else if (e.PropertyName == Circle.FillColorProperty.PropertyName)
			{
				mapPolygon.FillColor = circle.FillColor.ToWindowsColor();
			}
			else if (e.PropertyName == Circle.CenterProperty.PropertyName ||
					 e.PropertyName == Circle.RadiusProperty.PropertyName)
			{
				mapPolygon.Path = PositionsToGeopath(circle.ToCircumferencePositions());
			}
		}

		#endregion

		async Task UpdateIsShowingUser(bool moveToLocation = true)
		{
			if (Control == null || Element == null)
				return;

			if (Element.IsShowingUser)
			{
				var myGeolocator = new Geolocator();
				if (myGeolocator.LocationStatus != PositionStatus.NotAvailable &&
					myGeolocator.LocationStatus != PositionStatus.Disabled)
				{
					var userPosition = await myGeolocator.GetGeopositionAsync();
					if (userPosition?.Coordinate != null)
						LoadUserPosition(userPosition.Coordinate, moveToLocation);
				}

				if (Control == null || Element == null)
					return;

				if (_timer == null)
				{
					_timer = new DispatcherTimer();
					_timer.Tick += async (s, o) => await UpdateIsShowingUser(moveToLocation: false);
					_timer.Interval = TimeSpan.FromSeconds(15);
				}

				if (!_timer.IsEnabled)
					_timer.Start();
			}
			else if (_userPositionCircle != null && Control.Children.Contains(_userPositionCircle))
			{
				_timer.Stop();
				Control.Children.Remove(_userPositionCircle);
			}
		}

		async Task MoveToRegion(MapSpan span, MapAnimationKind animation = MapAnimationKind.Bow)
		{
			var nw = new BasicGeoposition
			{
				Latitude = span.Center.Latitude + span.LatitudeDegrees / 2,
				Longitude = span.Center.Longitude - span.LongitudeDegrees / 2
			};
			var se = new BasicGeoposition
			{
				Latitude = span.Center.Latitude - span.LatitudeDegrees / 2,
				Longitude = span.Center.Longitude + span.LongitudeDegrees / 2
			};
			var boundingBox = new GeoboundingBox(nw, se);
			_isRegionUpdatePending = !await Control.TrySetViewBoundsAsync(boundingBox, null, animation);
		}

		async Task UpdateVisibleRegion()
		{
			if (Control == null || Element == null)
				return;
			try
			{
				Geopoint nw, se = null;
				Control.GetLocationFromOffset(new Windows.Foundation.Point(0, 0), out nw);
				Control.GetLocationFromOffset(new Windows.Foundation.Point(Control.ActualWidth, Control.ActualHeight), out se);

				if (nw != null && se != null)
				{
					var boundingBox = new GeoboundingBox(nw.Position, se.Position);
					var center = new Position(boundingBox.Center.Latitude, boundingBox.Center.Longitude);
					var latitudeDelta = Math.Abs(nw.Position.Latitude - se.Position.Latitude);
					var longitudeDelta = Math.Abs(nw.Position.Longitude - se.Position.Longitude);
					await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
					{
						Element.SetVisibleRegion(new MapSpan(center, latitudeDelta, longitudeDelta));
					});
				}
			}
			catch (Exception)
			{
				return;
			}
		}

		void LoadUserPosition(Geocoordinate userCoordinate, bool center)
		{
			if (Control == null || Element == null)
				return;

			var userPosition = new BasicGeoposition
			{
				Latitude = userCoordinate.Point.Position.Latitude,
				Longitude = userCoordinate.Point.Position.Longitude
			};

			var point = new Geopoint(userPosition);

			if (_userPositionCircle == null)
			{
				_userPositionCircle = new Ellipse
				{
					Stroke = new SolidColorBrush(Colors.White),
					Fill = new SolidColorBrush(Colors.Blue),
					StrokeThickness = 2,
					Height = 20,
					Width = 20,
					Opacity = 50
				};
			}

			if (Control.Children.Contains(_userPositionCircle))
				Control.Children.Remove(_userPositionCircle);

			MapControl.SetLocation(_userPositionCircle, point);
			MapControl.SetNormalizedAnchorPoint(_userPositionCircle, new Windows.Foundation.Point(0.5, 0.5));

			Control.Children.Add(_userPositionCircle);

			if (center)
			{
				Control.Center = point;
				Control.ZoomLevel = 13;
			}
		}

		void UpdateMapType()
		{
			switch (Element.MapType)
			{
				case MapType.Street:
					Control.Style = MapStyle.Road;
					break;
				case MapType.Satellite:
					Control.Style = MapStyle.Aerial;
					break;
				case MapType.Hybrid:
					Control.Style = MapStyle.AerialWithRoads;
					break;
			}
		}

		void UpdateHasZoomEnabled()
		{
			Control.ZoomInteractionMode = Element.HasZoomEnabled
				? MapInteractionMode.GestureAndControl
				: MapInteractionMode.ControlOnly;
		}

		void UpdateHasScrollEnabled()
		{
			Control.PanInteractionMode = Element.HasScrollEnabled ? MapPanInteractionMode.Auto : MapPanInteractionMode.Disabled;
		}

		void OnMapTapped(MapControl sender, MapInputEventArgs args)
		{
			Element?.SendMapClicked(new Position(args.Location.Position.Latitude, args.Location.Position.Longitude));
		}
	}
}