From 740654ff5654b6f572ddb6be7b34991bb2d73d02 Mon Sep 17 00:00:00 2001
From: Andrei Nitescu <nitescua@yahoo.com>
Date: Mon, 1 Apr 2019 21:12:40 +0300
Subject: [PATCH] Map with ItemTemplateSelector (#5226)

* Map with ItemTemplateSelector

* Fixed Map test
---
 .../MapWithItemsSourceGallery.xaml            |  65 ++++---
 .../MapWithItemsSourceGallery.xaml.cs         |  10 +
 Xamarin.Forms.Core.UnitTests/MapTests.cs      | 180 +++++++++++-------
 Xamarin.Forms.Maps/Map.cs                     |  29 ++-
 4 files changed, 182 insertions(+), 102 deletions(-)

diff --git a/Xamarin.Forms.Controls/GalleryPages/MapWithItemsSourceGallery.xaml b/Xamarin.Forms.Controls/GalleryPages/MapWithItemsSourceGallery.xaml
index e48b7a9c3..5a8b1f528 100644
--- a/Xamarin.Forms.Controls/GalleryPages/MapWithItemsSourceGallery.xaml
+++ b/Xamarin.Forms.Controls/GalleryPages/MapWithItemsSourceGallery.xaml
@@ -2,34 +2,41 @@
 <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
 			 xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
 			 xmlns:map="clr-namespace:Xamarin.Forms.Maps;assembly=Xamarin.Forms.Maps"
+             xmlns:local="clr-namespace:Xamarin.Forms.Controls.GalleryPages"
 			 x:Class="Xamarin.Forms.Controls.GalleryPages.MapWithItemsSourceGallery">
-	<Grid>
-		<Grid.RowDefinitions>
-			<RowDefinition />
-			<RowDefinition Height="Auto" />
-		</Grid.RowDefinitions>
-		<map:Map ItemsSource="{Binding Places}"
-				 x:Name="_map">
-			<map:Map.ItemTemplate>
-				<DataTemplate>
-					<map:Pin Position="{Binding Position}"
-							 Address="{Binding Address}"
-							 Label="{Binding Description}" />
-				</DataTemplate>
-			</map:Map.ItemTemplate>
-		</map:Map>
-		<StackLayout Orientation="Horizontal"
-					 Grid.Row="1">
-			<Button Text="Add"
-					Command="{Binding AddPlaceCommand}" />
-			<Button Text="Remove"
-					Command="{Binding RemovePlaceCommand}" />
-			<Button Text="Clear"
-					Command="{Binding ClearPlacesCommand}" />
-			<Button Text="Update"
-					Command="{Binding UpdatePlacesCommand}" />
-			<Button Text="Replace"
-					Command="{Binding ReplacePlaceCommand}" />
-		</StackLayout>
-	</Grid>
+    <ContentPage.Resources>
+        <ResourceDictionary>
+            <local:MapItemTemplateSelector x:Key="MapItemTemplateSelector">
+                <local:MapItemTemplateSelector.DataTemplate>
+                    <DataTemplate>
+                        <map:Pin Position="{Binding Position}"
+                                 Address="{Binding Address}"
+                                 Label="{Binding Description}" />
+                    </DataTemplate>
+                </local:MapItemTemplateSelector.DataTemplate>
+            </local:MapItemTemplateSelector>
+        </ResourceDictionary>
+    </ContentPage.Resources>
+    <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition />
+            <RowDefinition Height="Auto" />
+        </Grid.RowDefinitions>
+        <map:Map x:Name="_map"
+                 ItemsSource="{Binding Places}"
+				 ItemTemplateSelector="{StaticResource MapItemTemplateSelector}" />
+        <StackLayout Orientation="Horizontal"
+                         Grid.Row="1">
+            <Button Text="Add"
+                        Command="{Binding AddPlaceCommand}" />
+            <Button Text="Remove"
+                        Command="{Binding RemovePlaceCommand}" />
+            <Button Text="Clear"
+                        Command="{Binding ClearPlacesCommand}" />
+            <Button Text="Update"
+                        Command="{Binding UpdatePlacesCommand}" />
+            <Button Text="Replace"
+                        Command="{Binding ReplacePlaceCommand}" />
+        </StackLayout>
+    </Grid>
 </ContentPage>
\ No newline at end of file
diff --git a/Xamarin.Forms.Controls/GalleryPages/MapWithItemsSourceGallery.xaml.cs b/Xamarin.Forms.Controls/GalleryPages/MapWithItemsSourceGallery.xaml.cs
index dd96aa353..708b2d738 100644
--- a/Xamarin.Forms.Controls/GalleryPages/MapWithItemsSourceGallery.xaml.cs
+++ b/Xamarin.Forms.Controls/GalleryPages/MapWithItemsSourceGallery.xaml.cs
@@ -152,4 +152,14 @@ namespace Xamarin.Forms.Controls.GalleryPages
 			}
 		}
 	}
+
+	class MapItemTemplateSelector : DataTemplateSelector
+	{
+		public DataTemplate DataTemplate { get; set; }
+
+		protected override DataTemplate OnSelectTemplate(object item, BindableObject container)
+		{
+			return DataTemplate;
+		}
+	}
 }
\ No newline at end of file
diff --git a/Xamarin.Forms.Core.UnitTests/MapTests.cs b/Xamarin.Forms.Core.UnitTests/MapTests.cs
index 251e9442e..dcf93fd88 100644
--- a/Xamarin.Forms.Core.UnitTests/MapTests.cs
+++ b/Xamarin.Forms.Core.UnitTests/MapTests.cs
@@ -11,140 +11,148 @@ namespace Xamarin.Forms.Core.UnitTests
 	public class MapTests : BaseTestFixture
 	{
 		[Test]
-		public void AddPin ()
+		public void AddPin()
 		{
-			var map = new Map ();
+			var map = new Map();
 
-			var home = new Pin {
+			var home = new Pin
+			{
 				Label = "Home",
-				Position = new Position (88, 2),
+				Position = new Position(88, 2),
 				Type = PinType.Place,
 				Address = "123 My Place"
 			};
 
-			map.Pins.Add (home);
+			map.Pins.Add(home);
 
-			Assert.AreEqual (map.Pins.Count, 1);
-			Assert.AreEqual (map.Pins[0].Label, "Home");
-			var mall = new Pin {
+			Assert.AreEqual(map.Pins.Count, 1);
+			Assert.AreEqual(map.Pins[0].Label, "Home");
+			var mall = new Pin
+			{
 				Label = "Mall",
-				Position = new Position (-12, -67),
+				Position = new Position(-12, -67),
 				Type = PinType.Place,
 				Address = "123 Fun"
 			};
 
-			map.Pins.Add (mall);
+			map.Pins.Add(mall);
 
-			Assert.AreEqual (map.Pins.Count, 2);
-			Assert.AreEqual (map.Pins[1].Position.Latitude, -12);
+			Assert.AreEqual(map.Pins.Count, 2);
+			Assert.AreEqual(map.Pins[1].Position.Latitude, -12);
 		}
 
 		[Test]
-		public void AddPinWithoutName ()
+		public void AddPinWithoutName()
 		{
-			var map = new Map ();
-			var noNamePin = new Pin {
-				Position = new Position (50, 50),
+			var map = new Map();
+			var noNamePin = new Pin
+			{
+				Position = new Position(50, 50),
 				Type = PinType.Generic,
 				Address = "123 Fun"
 			};
 
-			var exception = Assert.Throws<ArgumentException> (() => map.Pins.Add (noNamePin));
-			Assert.That (exception.Message, Is.EqualTo ("Pin must have a Label to be added to a map"));
+			var exception = Assert.Throws<ArgumentException>(() => map.Pins.Add(noNamePin));
+			Assert.That(exception.Message, Is.EqualTo("Pin must have a Label to be added to a map"));
 		}
 
 		[Test]
-		public void AddPinWithoutAddress ()
+		public void AddPinWithoutAddress()
 		{
-			var map = new Map ();
-			var noAddressPin = new Pin {
-				Position = new Position (37.9, -20.87),
+			var map = new Map();
+			var noAddressPin = new Pin
+			{
+				Position = new Position(37.9, -20.87),
 				Label = "I have no address",
 				Type = PinType.SearchResult
 			};
 
-			map.Pins.Add (noAddressPin);
-			Assert.AreEqual (map.Pins.Count, 1);
-			Assert.AreEqual (map.Pins[0].Label, "I have no address");
-			Assert.AreEqual (map.Pins[0].Address, null);
+			map.Pins.Add(noAddressPin);
+			Assert.AreEqual(map.Pins.Count, 1);
+			Assert.AreEqual(map.Pins[0].Label, "I have no address");
+			Assert.AreEqual(map.Pins[0].Address, null);
 		}
 
 		[Test]
-		public void Constructor ()
+		public void Constructor()
 		{
-			var center = new Position (15.5, 176);
-			var span = new MapSpan (center, 1, 2);
-			var map = new Map (span);
+			var center = new Position(15.5, 176);
+			var span = new MapSpan(center, 1, 2);
+			var map = new Map(span);
 
-			Assert.AreEqual (1, map.LastMoveToRegion.LatitudeDegrees);
-			Assert.AreEqual (2, map.LastMoveToRegion.LongitudeDegrees);
-			var position = new Position (15.5, 176);
-			Assert.AreEqual (position, map.LastMoveToRegion.Center);
+			Assert.AreEqual(1, map.LastMoveToRegion.LatitudeDegrees);
+			Assert.AreEqual(2, map.LastMoveToRegion.LongitudeDegrees);
+			var position = new Position(15.5, 176);
+			Assert.AreEqual(position, map.LastMoveToRegion.Center);
 		}
 
 		[Test]
-		public void RemovePin ()
+		public void RemovePin()
 		{
-			var map = new Map ();
-			var genericPlace = new Pin {
+			var map = new Map();
+			var genericPlace = new Pin
+			{
 				Label = "Generic",
-				Position = new Position (-12, -67),
+				Position = new Position(-12, -67),
 				Type = PinType.Generic,
 				Address = "XXX"
 			};
 
-			var mall = new Pin {
+			var mall = new Pin
+			{
 				Label = "Mall",
-				Position = new Position (-29, -87),
+				Position = new Position(-29, -87),
 				Type = PinType.Place,
 				Address = "123 Fun"
 			};
 
-			map.Pins.Add (genericPlace);
-			Assert.AreEqual (map.Pins.Count, 1);
+			map.Pins.Add(genericPlace);
+			Assert.AreEqual(map.Pins.Count, 1);
 
-			map.Pins.Add (mall);
-			Assert.AreEqual (map.Pins.Count, 2);
+			map.Pins.Add(mall);
+			Assert.AreEqual(map.Pins.Count, 2);
 
-			map.Pins.Remove (genericPlace);
-			Assert.AreEqual (map.Pins.Count, 1);
+			map.Pins.Remove(genericPlace);
+			Assert.AreEqual(map.Pins.Count, 1);
 
-			Assert.True (map.Pins.Contains (mall));
-			Assert.False (map.Pins.Contains (genericPlace));
+			Assert.True(map.Pins.Contains(mall));
+			Assert.False(map.Pins.Contains(genericPlace));
 		}
 
 		[Test]
-		public void VisibleRegion ()
+		public void VisibleRegion()
 		{
-			var map = new Map (new MapSpan (new Position (), 0, 0));
-			map.MoveToRegion (new MapSpan (new Position (1, 2), 3, 4));
-			Assert.AreEqual (null, map.VisibleRegion);
+			var map = new Map(new MapSpan(new Position(), 0, 0));
+			map.MoveToRegion(new MapSpan(new Position(1, 2), 3, 4));
+			Assert.AreEqual(null, map.VisibleRegion);
 
 			bool signaled = false;
-			MessagingCenter.Subscribe<Map, MapSpan> (this, "MapMoveToRegion", (s, a) => {
+			MessagingCenter.Subscribe<Map, MapSpan>(this, "MapMoveToRegion", (s, a) =>
+			{
 				signaled = true;
 				map.SetVisibleRegion(a);
 			}, map);
 
-			map.MoveToRegion (new MapSpan (new Position (1, 2), 3, 4));
-			Assert.AreEqual (new MapSpan (new Position (1, 2), 3, 4), map.LastMoveToRegion);
-			Assert.True (signaled);
+			map.MoveToRegion(new MapSpan(new Position(1, 2), 3, 4));
+			Assert.AreEqual(new MapSpan(new Position(1, 2), 3, 4), map.LastMoveToRegion);
+			Assert.True(signaled);
 		}
 
 		[Test]
-		public void VisibleRegionDoubleSet ()
+		public void VisibleRegionDoubleSet()
 		{
-			var map = new Map ();
+			var map = new Map();
 
 			bool signaled = false;
-			map.PropertyChanged += (sender, args) => {
+			map.PropertyChanged += (sender, args) =>
+			{
 				if (args.PropertyName == "VisibleRegion")
 					signaled = true;
 			};
 
 			map.SetVisibleRegion(map.VisibleRegion);
 
-			Assert.False (signaled);
+			Assert.False(signaled);
 		}
 
 		[Test]
@@ -292,12 +300,45 @@ namespace Xamarin.Forms.Core.UnitTests
 
 			map.ItemTemplate = GetItemTemplate("Address 2");
 			Assert.IsTrue(IsMapWithItemsSource(itemsSource, map));
-			foreach(Pin pin in map.Pins)
+			foreach (Pin pin in map.Pins)
 			{
 				Assert.IsTrue(pin.Address == "Address 2");
 			}
 		}
 
+		[Test]
+		public void ItemTemplateSelectorIsSet()
+		{
+			var map = new Map();
+
+			var itemsSource = new ObservableCollection<int>(Enumerable.Range(0, 3));
+			map.ItemsSource = itemsSource;
+			map.ItemTemplateSelector = new TestDataTemplateSelector("Address 2");
+
+			Assert.IsTrue(IsMapWithItemsSource(itemsSource, map));
+			foreach (Pin pin in map.Pins)
+			{
+				Assert.IsTrue(pin.Address == "Address 2");
+			}
+		}
+
+		[Test]
+		public void ItemTemplateTakesPrecendenceOverItemTemplateSelector()
+		{
+			var map = new Map();
+
+			var itemsSource = new ObservableCollection<int>(Enumerable.Range(0, 10));
+			map.ItemsSource = itemsSource;
+			map.ItemTemplate = GetItemTemplate("Address 1");
+			map.ItemTemplateSelector = new TestDataTemplateSelector("Address 2");
+
+			Assert.IsTrue(IsMapWithItemsSource(itemsSource, map));
+			foreach (Pin pin in map.Pins)
+			{
+				Assert.AreEqual(pin.Address, "Address 1");
+			}
+		}
+
 		[Test]
 		public void ItemsSourceTakePrecendenceOverPins()
 		{
@@ -395,16 +436,16 @@ namespace Xamarin.Forms.Core.UnitTests
 				return true;
 			}
 
-			if (map.ItemTemplate == null)
+			if (map.ItemTemplate == null && map.ItemTemplateSelector == null)
 			{
-				// If ItemsSource is set but ItemTemplate is not, there should not be any Pins
+				// If ItemsSource is set but neither ItemTemplate and ItemTemplate is, there should not be any Pins
 				return !map.Pins.Any();
 			}
 
 			int i = 0;
 			foreach (object item in itemsSource)
 			{
-				// Pins collection order are not tracked, so just make sure a Pin for item exists
+				// Pins collection order is not tracked, so just make sure a Pin for item exists
 				if (!map.Pins.Any(p => Equals(item, p.BindingContext)))
 				{
 					return false;
@@ -426,14 +467,19 @@ namespace Xamarin.Forms.Core.UnitTests
 			});
 		}
 
-		static DataTemplateSelector GetDataTemplateSelector()
+		static DataTemplateSelector GetDataTemplateSelector(string address = null)
 		{
-			return new TestDataTemplateSelector();
+			return new TestDataTemplateSelector(address);
 		}
 
 		class TestDataTemplateSelector : DataTemplateSelector
 		{
-			readonly DataTemplate dt = GetItemTemplate();
+			readonly DataTemplate dt;
+
+			public TestDataTemplateSelector(string address = null)
+			{
+				dt = GetItemTemplate(address);
+			}
 
 			protected override DataTemplate OnSelectTemplate(object item, BindableObject container)
 			{
diff --git a/Xamarin.Forms.Maps/Map.cs b/Xamarin.Forms.Maps/Map.cs
index a62cdee13..e1b8e5fb8 100644
--- a/Xamarin.Forms.Maps/Map.cs
+++ b/Xamarin.Forms.Maps/Map.cs
@@ -24,6 +24,9 @@ namespace Xamarin.Forms.Maps
 		public static readonly BindableProperty ItemTemplateProperty = BindableProperty.Create(nameof(ItemTemplate), typeof(DataTemplate), typeof(Map), default(DataTemplate),
 			propertyChanged: (b, o, n) => ((Map)b).OnItemTemplatePropertyChanged((DataTemplate)o, (DataTemplate)n));
 
+		public static readonly BindableProperty ItemTemplateSelectorProperty = BindableProperty.Create(nameof(ItemTemplateSelector), typeof(DataTemplateSelector), typeof(Map), default(DataTemplateSelector),
+			propertyChanged: (b, o, n) => ((Map)b).OnItemTemplateSelectorPropertyChanged());
+
 		readonly ObservableCollection<Pin> _pins = new ObservableCollection<Pin>();
 		MapSpan _visibleRegion;
 
@@ -82,6 +85,12 @@ namespace Xamarin.Forms.Maps
 			set { SetValue(ItemTemplateProperty, value); }
 		}
 
+		public DataTemplateSelector ItemTemplateSelector
+		{
+			get { return (DataTemplateSelector)GetValue(ItemTemplateSelectorProperty); }
+			set { SetValue(ItemTemplateSelectorProperty, value); }
+		}
+
 		[EditorBrowsable(EditorBrowsableState.Never)]
 		public void SetVisibleRegion(MapSpan value) => VisibleRegion = value;
 		public MapSpan VisibleRegion
@@ -153,6 +162,12 @@ namespace Xamarin.Forms.Maps
 			CreatePinItems();
 		}
 
+		void OnItemTemplateSelectorPropertyChanged()
+		{
+			_pins.Clear();
+			CreatePinItems();
+		}
+
 		void OnItemsSourceCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
 		{
 			switch (e.Action)
@@ -190,7 +205,7 @@ namespace Xamarin.Forms.Maps
 
 		void CreatePinItems()
 		{
-			if (ItemsSource == null || ItemTemplate == null)
+			if (ItemsSource == null || (ItemTemplate == null && ItemTemplateSelector == null))
 			{
 				return;
 			}
@@ -203,12 +218,14 @@ namespace Xamarin.Forms.Maps
 
 		void CreatePin(object newItem)
 		{
-			if (ItemTemplate == null)
-			{
-				return;
-			}
+			DataTemplate itemTemplate = ItemTemplate;
+			if (itemTemplate == null)
+				itemTemplate = ItemTemplateSelector?.SelectTemplate(newItem, this);
 
-			var pin = (Pin)ItemTemplate.CreateContent();
+			if (itemTemplate == null)
+				return;
+
+			var pin = (Pin)itemTemplate.CreateContent();
 			pin.BindingContext = newItem;
 			_pins.Add(pin);
 		}