Issue 15647: Fix selecting of an item in an Android ListView (#15660)

* Add repro sample (#15647)

* Fix selecting of an item in an Android ListView (#15647)

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue15647.cs

@@ -0,0 +1,90 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+using System.Collections.ObjectModel;
+using System;
+
+#if UITEST
+using Xamarin.Forms.Core.UITests;
+using Xamarin.UITest;
+using NUnit.Framework;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+#if UITEST
+	[Category(UITestCategories.ManualReview)]
+#endif
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 15647, "[Bug] Android ListView SelectedItem highlighting", PlatformAffected.Android)]
+	public class Issue15647 : TestContentPage
+	{
+		protected override void Init()
+		{
+			ViewModelIssue15647 viewModelIssue15647 = new ViewModelIssue15647();
+
+			Label testInstructionsLabel = new Label()
+			{
+				HorizontalTextAlignment = TextAlignment.Center,
+				Padding = new Thickness(3.0),
+				Text = "Click on the buttons to select the first or second item of the ListView." + Environment.NewLine +
+					"The correct item has to be marked as selected so that this test is successful.",
+			};
+
+			DataTemplate itemDataTemplate = new DataTemplate(() =>
+			{
+				Label itemLabel = new Label();
+				itemLabel.SetBinding(Label.TextProperty, ".");
+				return new ViewCell()
+				{
+					View = itemLabel,
+				};
+			});
+			ListView itemsListView = new ListView()
+			{
+				// Header = "Header",
+				ItemTemplate = itemDataTemplate,
+			};
+			itemsListView.SetBinding(ListView.ItemsSourceProperty, nameof(ViewModelIssue15647.Items));
+
+			Button selectFirstItemButton = new Button()
+			{
+				Text = "Select first item",
+			};
+			selectFirstItemButton.Clicked += (_, __) =>
+			{
+				Console.WriteLine(itemsListView.SelectedItem);
+				itemsListView.SelectedItem = viewModelIssue15647.Items[0];
+				Console.WriteLine(itemsListView.SelectedItem);
+			};
+
+			Button selectSecondItemButton = new Button()
+			{
+				Text = "Select second item",
+			};
+			selectSecondItemButton.Clicked += (_, __) =>
+			{
+				Console.WriteLine(itemsListView.SelectedItem);
+				itemsListView.SelectedItem = viewModelIssue15647.Items[1];
+				Console.WriteLine(itemsListView.SelectedItem);
+			};
+
+			Content = new StackLayout()
+			{
+				Children = { testInstructionsLabel, selectFirstItemButton, selectSecondItemButton, itemsListView },
+			};
+
+			BindingContext = viewModelIssue15647;
+		}
+	}
+
+	[Preserve(AllMembers = true)]
+	public class ViewModelIssue15647
+	{
+		public ViewModelIssue15647()
+		{
+			Items = new ObservableCollection<string>() { "first item", "second item" };
+		}
+
+		public ObservableCollection<string> Items { get; }
+	}
+}

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

@@ -1871,6 +1871,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Issue15305.xaml.cs">
       <DependentUpon>Issue15305.xaml</DependentUpon>
     </Compile>
+	<Compile Include="$(MSBuildThisFileDirectory)Issue15647.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Controls\MyCollectionView.xaml.cs">
       <DependentUpon>MyCollectionView.xaml</DependentUpon>
       <SubType>Code</SubType>

Xamarin.Forms.Platform.Android/Renderers/ListViewAdapter.cs

@@ -672,7 +672,7 @@ void SelectItem(object item)
 			int position = TemplatedItemsView.TemplatedItems.GetGlobalIndexOfItem(item);
 			AView view = null;
 			if (position != -1)
-				view = _realListView.GetChildAt(position + 1 - _realListView.FirstVisiblePosition);
+				view = _realListView.GetChildAt(position + _realListView.HeaderViewsCount - _realListView.FirstVisiblePosition);
 
 			Select(position, view);
 		}