Implement CollectionView grouping on Android (#7199)

* Move all the header/footer adjustment to IItemsViewSource
fixes #7121
fixes #7102
partially implements #3172
fixes #7243

* Fix selection bugs introduced by header/footer on Android

* Implement grouping for CollectionView on Android

* Enable grouping tests for Android

* Naming and comment cleanup

* Update Xamarin.Forms.Platform.Android/CollectionView/ListSource.cs

Co-Authored-By: Gerald Versluis <gerald.versluis@microsoft.com>

* Update Xamarin.Forms.Platform.Android/CollectionView/ObservableGroupedSource.cs

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/CollectionViewGrouping.cs

@@ -29,7 +29,7 @@ protected override void Init()
 #endif
 		}
 
-#if UITEST && __IOS__ // Grouping is not implemented on Android yet
+#if UITEST 
 		[Test]
 		public void RemoveSelectedItem()
 		{
@@ -88,8 +88,6 @@ public void MoveGroup()
 			RunningApp.WaitForElement("MoveGroup");
 			RunningApp.Tap("MoveGroup");
 		}
-
-
 #endif
 	}
 }

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue7102.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using Xamarin.Forms.Core.UITests;
+using Xamarin.UITest;
+using NUnit.Framework;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+#if UITEST
+	[Category(UITestCategories.CollectionView)]
+#endif
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 7102, "[Bug] CollectionView Header cause delay to adding items.",
+		PlatformAffected.Android)]
+	public class Issue7102 : TestNavigationPage
+	{
+		protected override void Init()
+		{
+#if APP
+			FlagTestHelpers.SetCollectionViewTestFlag();
+
+			PushAsync(new GalleryPages.CollectionViewGalleries.ObservableCodeCollectionViewGallery(grid: false));
+#endif
+		}
+
+#if UITEST
+		[Test]
+		public void HeaderDoesNotBreakIndexes()
+		{
+			RunningApp.WaitForElement("entryInsert");
+			RunningApp.Tap("entryInsert");
+			RunningApp.ClearText();
+			RunningApp.EnterText("1");
+			RunningApp.Tap("Insert");
+
+			// If the bug is still present, then there will be 
+			// two "Item: 0" items instead of the newly inserted item
+			// Or the header will have disappeared
+			RunningApp.WaitForElement("Inserted");
+			RunningApp.WaitForElement("This is the header");
+		}
+#endif
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -34,6 +34,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)NestedCollectionViews.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ShellGestures.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ShellBackButtonBehavior.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue7102.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ShellInsets.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)CollectionViewGrouping.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue5412.cs" />

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

@@ -17,10 +17,10 @@ protected CollectionModifier(CollectionView cv, string buttonText)
 				HorizontalOptions = LayoutOptions.Fill
 			};
 
-			var button = new Button { Text = buttonText, AutomationId = $"btn{buttonText}" };
-			var label = new Label { Text = LabelText, VerticalTextAlignment = TextAlignment.Center };
+			var button = new Button { Text = buttonText, AutomationId = $"btn{buttonText}", HeightRequest = 20, FontSize = 10 };
+			var label = new Label { Text = LabelText, VerticalTextAlignment = TextAlignment.Center, FontSize = 10 };
 
-			Entry = new Entry { Keyboard = Keyboard.Numeric, Text = InitialEntryText, WidthRequest = 100, AutomationId = $"entry{buttonText}" };
+			Entry = new Entry { Keyboard = Keyboard.Numeric, Text = InitialEntryText, WidthRequest = 100, FontSize = 10, AutomationId = $"entry{buttonText}" };
 
 			layout.Children.Add(label);
 			layout.Children.Add(Entry);

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/GroupingGalleries/BasicGrouping.xaml

@@ -3,7 +3,7 @@
              xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
              x:Class="Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.GroupingGalleries.BasicGrouping">
 	<ContentPage.Content>
-		<CollectionView x:Name="CollectionView" IsGrouped="True">
+		<CollectionView x:Name="CollectionView" IsGrouped="True" Header="This is a header" Footer="Hey, a footer."> 
 
 			<CollectionView.ItemTemplate>
 				<DataTemplate>

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/GroupingGalleries/BasicGrouping.xaml.cs

@@ -11,12 +11,12 @@
 namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.GroupingGalleries
 {
 	[XamlCompilation(XamlCompilationOptions.Compile)]
-	[Preserve (AllMembers = true)]
+	[Preserve(AllMembers = true)]
 	public partial class BasicGrouping : ContentPage
 	{
-		public BasicGrouping ()
+		public BasicGrouping()
 		{
-			InitializeComponent ();
+			InitializeComponent();
 
 			CollectionView.ItemsSource = new SuperTeams();
 		}

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/GroupingGalleries/GridGrouping.xaml

@@ -0,0 +1,42 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             mc:Ignorable="d"
+             x:Class="Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.GroupingGalleries.GridGrouping">
+    <ContentPage.Content>
+        <CollectionView x:Name="CollectionView" IsGrouped="True" Header="This is a header" Footer="This is a footer.">
+
+            <CollectionView.ItemsLayout>
+                <GridItemsLayout Span="2" Orientation="Vertical"></GridItemsLayout>
+            </CollectionView.ItemsLayout>
+
+            <CollectionView.ItemTemplate>
+                <DataTemplate>
+                    <StackLayout>
+                        <Label Text="{Binding Name}" Margin="5,0,0,0"/>
+                    </StackLayout>
+                </DataTemplate>
+            </CollectionView.ItemTemplate>
+
+            <CollectionView.GroupHeaderTemplate>
+                <DataTemplate>
+
+                    <Label Text="{Binding Name}" BackgroundColor="LightGreen" FontSize="16" FontAttributes="Bold"/>
+
+                </DataTemplate>
+            </CollectionView.GroupHeaderTemplate>
+
+            <CollectionView.GroupFooterTemplate>
+                <DataTemplate>
+                    <StackLayout>
+                        <Label Text="{Binding Count, StringFormat='{}Total members: {0:D}'}" BackgroundColor="Orange" 
+							   Margin="0,0,0,15"/>
+                    </StackLayout>
+                </DataTemplate>
+            </CollectionView.GroupFooterTemplate>
+
+        </CollectionView>
+    </ContentPage.Content>
+</ContentPage>

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/GroupingGalleries/GridGrouping.xaml.cs

@@ -0,0 +1,14 @@
+using Xamarin.Forms.Xaml;
+
+namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.GroupingGalleries
+{
+	[XamlCompilation(XamlCompilationOptions.Compile)]
+	public partial class GridGrouping : ContentPage
+	{
+		public GridGrouping()
+		{
+			InitializeComponent();
+			CollectionView.ItemsSource = new SuperTeams();
+		}
+	}
+}

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/GroupingGalleries/GroupingGallery.cs

@@ -32,6 +32,8 @@ public GroupingGallery()
 							new SwitchGrouping(), Navigation),
 						GalleryBuilder.NavButton("Grouping, Observable", () =>
 							new ObservableGrouping(), Navigation),
+						GalleryBuilder.NavButton("Grouping, Grid", () =>
+							new GridGrouping(), Navigation),
 					}
 				}
 			};

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/GroupingGalleries/ObservableGrouping.cs

@@ -10,7 +10,7 @@ public ObservableGrouping()
 			Title = "Observable Grouped List";
 
 			var buttonStyle = new Style(typeof(Button)) { };
-			buttonStyle.Setters.Add(new Setter() { Property = Button.HeightRequestProperty, Value = 20 });
+			buttonStyle.Setters.Add(new Setter() { Property = Button.HeightRequestProperty, Value = 30 });
 			buttonStyle.Setters.Add(new Setter() { Property = Button.FontSizeProperty, Value = 10 });
 
 			var layout = new Grid
@@ -34,6 +34,8 @@ public ObservableGrouping()
 
 			var collectionView = new CollectionView
 			{
+				Header = "This is a header",
+				Footer = "Hey, I'm a footer. Look at me!",
 				ItemTemplate = ItemTemplate(),
 				GroupFooterTemplate = GroupFooterTemplate(),
 				GroupHeaderTemplate = GroupHeaderTemplate(),
@@ -102,7 +104,15 @@ public ObservableGrouping()
 				Style = buttonStyle };
 			groupRemover.Clicked += (obj, args) => {
 				itemsSource?.Remove(itemsSource[0]);
-				groupRemover.Text = $"Remove {itemsSource[0].Name}";
+				if (itemsSource.Count > 0)
+				{
+					groupRemover.Text = $"Remove {itemsSource[0].Name}";
+				}
+				else
+				{
+					groupRemover.Text = "";
+					groupRemover.IsEnabled = false;
+				}
 				mover.Text = $"Move Selected To {itemsSource[0].Name}";
 			};
 

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/HeaderFooterGalleries/FooterOnlyString.xaml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             mc:Ignorable="d"
+             x:Class="Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.HeaderFooterGalleries.FooterOnlyString">
+  <ContentPage.Content>
+        <CollectionView x:Name="CollectionView" Footer="This is a footer">
+
+        </CollectionView>
+    </ContentPage.Content>
+</ContentPage>

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/HeaderFooterGalleries/FooterOnlyString.xaml.cs

@@ -0,0 +1,25 @@
+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.HeaderFooterGalleries
+{
+	[XamlCompilation(XamlCompilationOptions.Compile)]
+	public partial class FooterOnlyString : ContentPage
+	{
+		readonly DemoFilteredItemSource _demoFilteredItemSource = new DemoFilteredItemSource(20);
+
+		public FooterOnlyString()
+		{
+			InitializeComponent();
+
+			CollectionView.ItemTemplate = ExampleTemplates.PhotoTemplate();
+			CollectionView.ItemsSource = _demoFilteredItemSource.Items;
+		}
+	}
+}

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/HeaderFooterGalleries/HeaderFooterGallery.cs

@@ -20,6 +20,7 @@ public HeaderFooterGallery()
 						GalleryBuilder.NavButton("Header/Footer (Forms View)", () => new HeaderFooterView(), Navigation),
 						GalleryBuilder.NavButton("Header/Footer (Template)", () => new HeaderFooterTemplate(), Navigation),
 						GalleryBuilder.NavButton("Header/Footer (Grid)", () => new HeaderFooterGrid(), Navigation),
+						GalleryBuilder.NavButton("Footer Only (String)", () => new FooterOnlyString(), Navigation),
 					}
 				}
 			};

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

@@ -25,7 +25,8 @@ public ObservableCodeCollectionViewGallery(ItemsLayoutOrientation orientation =
 
 			var itemTemplate = ExampleTemplates.PhotoTemplate();
 
-			var collectionView = new CollectionView {ItemsLayout = itemsLayout, ItemTemplate = itemTemplate, AutomationId = "collectionview" };
+			var collectionView = new CollectionView {ItemsLayout = itemsLayout, ItemTemplate = itemTemplate,
+				AutomationId = "collectionview", Header = "This is the header" };
 
 			var generator = new ItemsSourceGenerator(collectionView, initialItems, ItemsSourceType.ObservableCollection);
 

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

@@ -17,7 +17,7 @@
 
             <Button AutomationId="DirectUpdate" HeightRequest="35" FontSize="10" Text="Clear CV selection and add Items 0 and 3" Clicked="DirectUpdateClicked" />
 
-            <CollectionView x:Name="CollectionView" ItemsSource="{Binding Items}" 
+            <CollectionView x:Name="CollectionView" ItemsSource="{Binding Items}" Header="This is the header"
                             SelectionMode="Multiple" SelectedItems="{Binding SelectedItems}">
                 <CollectionView.ItemTemplate>
                     <DataTemplate>

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

@@ -15,7 +15,7 @@
 
 			<Label x:Name="SelectedItemsCommand" Grid.Row="2"/>
 
-            <CollectionView x:Name="CollectionView" Grid.Row="3" />
+            <CollectionView x:Name="CollectionView" Grid.Row="3" Header="This is the header" />
 
         </Grid>
     </ContentPage.Content>

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

@@ -7,7 +7,7 @@
 
             <Label Text="The CollectionView below should have several items already selected."/>
 
-            <CollectionView x:Name="CollectionView" Grid.Row="3">
+            <CollectionView x:Name="CollectionView" Grid.Row="3" Header="This is the header">
                 <CollectionView.ItemsLayout>
                     <GridItemsLayout Span="4" Orientation="Vertical"></GridItemsLayout>
                 </CollectionView.ItemsLayout>

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

@@ -9,8 +9,8 @@
         <StackLayout>
 
             <Label x:Name="Result" Text="Pending..."></Label>
-            
-            <CollectionView ItemsSource="{Binding Items}"
+
+            <CollectionView ItemsSource="{Binding Items}" Header="This is the header"
                     SelectionMode="Single"
                     SelectionChangedCommandParameter="{Binding SelectedItem,Source={x:Reference MyCollectionView}}"
                     SelectedItem="{Binding SelectedItem, Mode=TwoWay}"

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

@@ -41,7 +41,7 @@
 
 			<Label x:Name="SelectedItemsCommand" Grid.Row="3" HeightRequest="50" Margin="2" />
 
-			<CollectionView x:Name="CollectionView" Grid.Row="4">
+            <CollectionView x:Name="CollectionView" Grid.Row="4" Header="This is the header">
 				<CollectionView.ItemsLayout>
 					<GridItemsLayout Span="3" Orientation="Vertical"></GridItemsLayout>
 				</CollectionView.ItemsLayout>

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

@@ -50,11 +50,17 @@
     <EmbeddedResource Update="GalleryPages\BindableLayoutGalleryPage.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
+    <EmbeddedResource Update="GalleryPages\CollectionViewGalleries\GroupingGalleries\GridGrouping.xaml">
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
+    <EmbeddedResource Update="GalleryPages\CollectionViewGalleries\HeaderFooterGalleries\FooterOnlyString.xaml">
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
     <EmbeddedResource Update="GalleryPages\CharacterSpacingGallery.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
     <EmbeddedResource Update="GalleryPages\CollectionViewGalleries\EmptyViewGalleries\EmptyViewSwapGallery.xaml">
-	<Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+	    <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
     <EmbeddedResource Update="GalleryPages\CollectionViewGalleries\NestedGalleries\NestedCollectionViewGallery.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>