Merge branch '4.0.0'

.nuspec/Xamarin.Forms.Maps.nuspec

@@ -64,9 +64,5 @@
     <file src="..\Xamarin.Forms.Maps\bin\$Configuration$\netstandard2.0\Xamarin.Forms.Maps.dll" target="lib\tizen40" />
     <file src="..\docs\Xamarin.Forms.Maps.xml" target="lib\tizen40" />
 
-    <!-- Xaml Design-time Stuff -->
-    <file src="..\Xamarin.Forms.Maps.Design\bin\$Configuration$\Xamarin.Forms.Maps.Design.dll" target="lib\netstandard2.0\Design" />
-    <file src="..\Xamarin.Forms.Maps.Design\bin\$Configuration$\Xamarin.Forms.Maps.Design.dll" target="lib\netstandard1.0\Design" />
-
 </files>
 </package>

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/ExampleTemplates.cs

@@ -21,6 +21,7 @@ public static DataTemplate PhotoTemplate()
 					HeightRequest = 100, WidthRequest = 100,
 					HorizontalOptions = LayoutOptions.Center,
 					VerticalOptions = LayoutOptions.Center,
+					Margin = new Thickness(2, 5, 2, 2),
 					AutomationId = "photo"
 				};
 
@@ -30,7 +31,8 @@ public static DataTemplate PhotoTemplate()
 				{
 					FontSize = 12,
 					HorizontalOptions = LayoutOptions.Fill,
-					HorizontalTextAlignment = TextAlignment.Center
+					HorizontalTextAlignment = TextAlignment.Center,
+					Margin = new Thickness(2, 0, 2, 2)
 				};
 
 				caption.SetBinding(Label.TextProperty, new Binding("Caption"));

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/SelectionGalleries/PreselectedItemGallery.xaml.cs

@@ -1,10 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-using Xamarin.Forms;
+using System.Linq;
 using Xamarin.Forms.Xaml;
 
 namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.SelectionGalleries
@@ -14,9 +8,9 @@ public partial class PreselectedItemGallery : ContentPage
 	{
 		readonly DemoFilteredItemSource _demoFilteredItemSource = new DemoFilteredItemSource();
 
-		public PreselectedItemGallery ()
+		public PreselectedItemGallery()
 		{
-			InitializeComponent ();
+			InitializeComponent();
 
 			CollectionView.ItemTemplate = ExampleTemplates.PhotoTemplate();
 			CollectionView.ItemsSource = _demoFilteredItemSource.Items;

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/SelectionGalleries/PreselectedItemsGallery.xaml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.SelectionGalleries.PreselectedItemsGallery">
+    <ContentPage.Content>
+        <StackLayout Margin="10">
+
+            <Label Text="The CollectionView below should have several items already selected."/>
+
+            <CollectionView x:Name="CollectionView" Grid.Row="3">
+                <CollectionView.ItemsLayout>
+                    <GridItemsLayout Span="4" Orientation="Vertical"></GridItemsLayout>
+                </CollectionView.ItemsLayout>
+            </CollectionView>
+        </StackLayout>
+    </ContentPage.Content>
+</ContentPage>

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/SelectionGalleries/PreselectedItemsGallery.xaml.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+using Xamarin.Forms;
+using Xamarin.Forms.Xaml;
+
+namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.SelectionGalleries
+{
+	[XamlCompilation(XamlCompilationOptions.Compile)]
+	public partial class PreselectedItemsGallery : ContentPage
+	{
+		readonly DemoFilteredItemSource _demoFilteredItemSource = new DemoFilteredItemSource();
+
+		public PreselectedItemsGallery()
+		{
+			InitializeComponent();
+
+			CollectionView.ItemTemplate = ExampleTemplates.PhotoTemplate();
+			CollectionView.ItemsSource = _demoFilteredItemSource.Items;
+
+			CollectionView.SelectedItems.Add(_demoFilteredItemSource.Items.Skip(2).First());
+			CollectionView.SelectedItems.Add(_demoFilteredItemSource.Items.Skip(4).First());
+			CollectionView.SelectedItems.Add(_demoFilteredItemSource.Items.Skip(5).First());
+
+			CollectionView.SelectionMode = SelectionMode.Multiple;
+		}
+	}
+}

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/SelectionGalleries/SelectionGallery.cs

@@ -20,6 +20,8 @@ public SelectionGallery()
 							new SelectionModeGallery(), Navigation),
 						GalleryBuilder.NavButton("Preselected Item", () =>
 							new PreselectedItemGallery(), Navigation),
+						GalleryBuilder.NavButton("Preselected Items", () =>
+							new PreselectedItemsGallery(), Navigation),
 					}
 				}
 			};

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/SelectionGalleries/SelectionModeGallery.xaml.cs

@@ -56,7 +56,11 @@ void UpdateSelectionInfoCommand()
 		{
 			var current = "[none]";
 
-			if (CollectionView.SelectedItem != null)
+			if(CollectionView.SelectionMode == SelectionMode.Multiple)
+			{
+				current = ToList(CollectionView?.SelectedItems);
+			}
+			else if (CollectionView.SelectionMode == SelectionMode.Single)
 			{
 				current = ((CollectionViewGalleryTestItem)CollectionView?.SelectedItem)?.Caption;
 			}

Xamarin.Forms.Controls/Xamarin.Forms.Controls.csproj

@@ -45,6 +45,9 @@
     </Compile>
     <Compile Update="GalleryPages\CollectionViewGalleries\EmptyViewGalleries\EmptyViewLoadSimulateGallery.xaml.cs">
       <DependentUpon>EmptyViewLoadSimulateGallery.xaml</DependentUpon>
+      </Compile>
+    <Compile Update="GalleryPages\CollectionViewGalleries\SelectionGalleries\PreselectedItemsGallery.xaml.cs">
+      <DependentUpon>PreselectedItemsGallery.xaml</DependentUpon>
     </Compile>
     <Compile Update="GalleryPages\VisualStateManagerGalleries\OnPlatformExample.xaml.cs">
       <DependentUpon>OnPlatformExample.xaml</DependentUpon>
@@ -53,6 +56,9 @@
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
     <EmbeddedResource Update="GalleryPages\CollectionViewGalleries\EmptyViewGalleries\EmptyViewSwapGallery.xaml">
+	<Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
+    <EmbeddedResource Update="GalleryPages\CollectionViewGalleries\SelectionGalleries\PreselectedItemsGallery.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
     <EmbeddedResource Update="GalleryPages\MapWithItemsSourceGallery.xaml">

Xamarin.Forms.Core/Items/SelectableItemsView.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Windows.Input;
 
 namespace Xamarin.Forms
@@ -7,25 +8,41 @@ public class SelectableItemsView : ItemsView
 	{
 		public static readonly BindableProperty SelectionModeProperty =
 			BindableProperty.Create(nameof(SelectionMode), typeof(SelectionMode), typeof(SelectableItemsView),
-				SelectionMode.None);
+				SelectionMode.None, propertyChanged: SelectionModePropertyChanged );
 
 		public static readonly BindableProperty SelectedItemProperty =
 			BindableProperty.Create(nameof(SelectedItem), typeof(object), typeof(SelectableItemsView), default(object),
 				propertyChanged: SelectedItemPropertyChanged);
 
+		static readonly BindablePropertyKey SelectedItemsPropertyKey =
+			BindableProperty.CreateReadOnly(nameof(SelectedItems), typeof(IList<object>), typeof(SelectableItemsView), null);
+
+		public static readonly BindableProperty SelectedItemsProperty = SelectedItemsPropertyKey.BindableProperty;
+
 		public static readonly BindableProperty SelectionChangedCommandProperty =
 			BindableProperty.Create(nameof(SelectionChangedCommand), typeof(ICommand), typeof(SelectableItemsView));
 
 		public static readonly BindableProperty SelectionChangedCommandParameterProperty =
 			BindableProperty.Create(nameof(SelectionChangedCommandParameter), typeof(object),
 				typeof(SelectableItemsView));
 
+		public SelectableItemsView()
+		{
+			var selectionList = new SelectionList(this);
+			SetValue(SelectedItemsPropertyKey, selectionList);
+		}
+
 		public object SelectedItem
 		{
 			get => GetValue(SelectedItemProperty);
 			set => SetValue(SelectedItemProperty, value);
 		}
 
+		public IList<object> SelectedItems
+		{
+			get => (IList<object>)GetValue(SelectedItemsProperty);
+		}
+
 		public ICommand SelectionChangedCommand
 		{
 			get => (ICommand)GetValue(SelectionChangedCommandProperty);
@@ -50,12 +67,14 @@ protected virtual void OnSelectionChanged(SelectionChangedEventArgs args)
 		{
 		}
 
-		static void SelectedItemPropertyChanged(BindableObject bindable, object oldValue, object newValue)
+		internal void SelectedItemsPropertyChanged(IList<object> oldSelection, IList<object> newSelection)
 		{
-			var selectableItemsView = (SelectableItemsView)bindable;
-
-			var args = new SelectionChangedEventArgs(oldValue, newValue);
+			SelectionPropertyChanged(this, new SelectionChangedEventArgs(oldSelection, newSelection));
+			OnPropertyChanged(SelectedItemsProperty.PropertyName);
+		}
 
+		static void SelectionPropertyChanged(SelectableItemsView selectableItemsView, SelectionChangedEventArgs args)
+		{
 			var command = selectableItemsView.SelectionChangedCommand;
 
 			if (command != null)
@@ -72,5 +91,68 @@ static void SelectedItemPropertyChanged(BindableObject bindable, object oldValue
 
 			selectableItemsView.OnSelectionChanged(args);
 		}
+
+		static void SelectedItemPropertyChanged(BindableObject bindable, object oldValue, object newValue)
+		{
+			var selectableItemsView = (SelectableItemsView)bindable;
+
+			var args = new SelectionChangedEventArgs(oldValue, newValue);
+
+			SelectionPropertyChanged(selectableItemsView, args);
+		}
+
+		static void SelectionModePropertyChanged(BindableObject bindable, object oldValue, object newValue)
+		{
+			var selectableItemsView = (SelectableItemsView)bindable;
+
+			var oldMode = (SelectionMode)oldValue;
+			var newMode = (SelectionMode)newValue;
+
+			IList<object> previousSelection = new List<object>();
+			IList<object> newSelection = new List<object>();
+
+			switch (oldMode)
+			{
+				case SelectionMode.None:
+					break;
+				case SelectionMode.Single:
+					if (selectableItemsView.SelectedItem != null)
+					{
+						previousSelection.Add(selectableItemsView.SelectedItem);
+					}
+					break;
+				case SelectionMode.Multiple:
+					previousSelection = selectableItemsView.SelectedItems;
+					break;
+			}
+
+			switch (newMode)
+			{
+				case SelectionMode.None:
+					break;
+				case SelectionMode.Single:
+					if (selectableItemsView.SelectedItem != null)
+					{
+						newSelection.Add(selectableItemsView.SelectedItem);
+					}
+					break;
+				case SelectionMode.Multiple:
+					newSelection = selectableItemsView.SelectedItems;
+					break;
+			}
+
+			if (previousSelection.Count == newSelection.Count)
+			{
+				if (previousSelection.Count == 0 || (previousSelection[0] == newSelection[0]))
+				{
+					// Both selections are empty or have the same single item; no reason to signal a change
+					return;
+				}
+			}
+
+			var args = new SelectionChangedEventArgs(previousSelection, newSelection);
+
+			SelectionPropertyChanged(selectableItemsView, args);
+		}
 	}
 }

Xamarin.Forms.Core/Items/SelectionChangedEventArgs.cs

@@ -16,10 +16,10 @@ internal SelectionChangedEventArgs(object previousSelection, object currentSelec
 			CurrentSelection = currentSelection != null ? new List<object>(1) { currentSelection } : s_empty;
 		}
 
-		internal SelectionChangedEventArgs(List<object> previousSelection, List<object> currentSelection)
+		internal SelectionChangedEventArgs(IList<object> previousSelection, IList<object> currentSelection)
 		{
-			PreviousSelection = previousSelection ?? throw new ArgumentNullException(nameof(previousSelection));
-			CurrentSelection = currentSelection ?? throw new ArgumentNullException(nameof(currentSelection));
+			PreviousSelection = new List<object>(previousSelection ?? throw new ArgumentNullException(nameof(previousSelection)));
+			CurrentSelection = new List<object>(currentSelection ?? throw new ArgumentNullException(nameof(currentSelection)));
 		}
 	}
 }