CollectionView Header/Footer/EmptyView issues when adding/removing items. (#24830)

* Fixed: 11896 - CollectionView Header/Footer/EmptyView issues when adding/removing items

* updated Items/ItemsViewHandler.Android.cs

* Added testcases.

* Added ios fix.

* updated Issue11896.cs

* updated Issue11896.cs

* Added output images.

* ios images updated.

Author: Vignesh-SF3580

src/Controls/src/Core/Handlers/Items/Android/Adapters/AdapterNotifier.cs

@@ -29,9 +29,6 @@ public void NotifyItemInserted(IItemsViewSource source, int startIndex)
 			if (IsValidAdapter())
 			{
 				_adapter.NotifyItemInserted(startIndex);
-
-				var changedCount = _adapter.ItemCount - startIndex;
-				_adapter.NotifyItemRangeChanged(startIndex, changedCount);
 			}
 		}
 
@@ -40,10 +37,6 @@ public void NotifyItemMoved(IItemsViewSource source, int fromPosition, int toPos
 			if (IsValidAdapter())
 			{
 				_adapter.NotifyItemMoved(fromPosition, toPosition);
-
-				var minPosition = System.Math.Min(fromPosition, toPosition);
-				var changedCount = _adapter.ItemCount - minPosition;
-				_adapter.NotifyItemRangeChanged(minPosition, changedCount);
 			}
 		}
 
@@ -58,9 +51,6 @@ public void NotifyItemRangeInserted(IItemsViewSource source, int startIndex, int
 			if (IsValidAdapter())
 			{
 				_adapter.NotifyItemRangeInserted(startIndex, count);
-
-				var changedCount = _adapter.ItemCount - startIndex;
-				_adapter.NotifyItemRangeChanged(startIndex, changedCount);
 			}
 		}
 
@@ -69,9 +59,6 @@ public void NotifyItemRangeRemoved(IItemsViewSource source, int startIndex, int
 			if (IsValidAdapter())
 			{
 				_adapter.NotifyItemRangeRemoved(startIndex, count);
-
-				var changedCount = _adapter.ItemCount - startIndex;
-				_adapter.NotifyItemRangeChanged(startIndex, changedCount);
 			}
 		}
 
@@ -80,9 +67,6 @@ public void NotifyItemRemoved(IItemsViewSource source, int startIndex)
 			if (IsValidAdapter())
 			{
 				_adapter.NotifyItemRemoved(startIndex);
-
-				var changedCount = _adapter.ItemCount - startIndex;
-				_adapter.NotifyItemRangeChanged(startIndex, changedCount);
 			}
 		}
 

src/Controls/src/Core/Handlers/Items/Android/MauiRecyclerView.cs

@@ -567,11 +567,12 @@ internal void UpdateEmptyViewVisibility()
 					itemCount++;
 			}
 
-			var showEmptyView = ItemsView?.EmptyView != null && ItemsViewAdapter.ItemCount == itemCount;
+			var showEmptyView = (ItemsView?.EmptyView is not null || ItemsView?.EmptyViewTemplate is not null) && ItemsViewAdapter.ItemCount == itemCount;
 
 			var currentAdapter = GetAdapter();
 			if (showEmptyView && currentAdapter != _emptyViewAdapter)
 			{
+				GetRecycledViewPool().Clear();
 				SwapAdapter(_emptyViewAdapter, true);
 
 				// TODO hartez 2018/10/24 17:34:36 If this works, cache this layout manager as _emptyLayoutManager	
@@ -580,6 +581,7 @@ internal void UpdateEmptyViewVisibility()
 			}
 			else if (!showEmptyView && currentAdapter != ItemsViewAdapter)
 			{
+				GetRecycledViewPool().Clear();
 				SwapAdapter(ItemsViewAdapter, true);
 				UpdateLayoutManager();
 			}

src/Controls/src/Core/Handlers/Items/iOS/ItemsViewController.cs

@@ -567,7 +567,7 @@ protected virtual void HandleFormsElementMeasureInvalidated(VisualElement formsE
 		internal void UpdateView(object view, DataTemplate viewTemplate, ref UIView uiView, ref VisualElement formsElement)
 		{
 			// Is view set on the ItemsView?
-			if (view == null)
+			if (view is null && viewTemplate is null)
 			{
 				if (formsElement != null)
 				{

src/Controls/tests/TestCases.Android.Tests/snapshots/android/CollectionViewHeaderBlankWhenLastItemRemoved.png

@@ -0,0 +1,57 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="Maui.Controls.Sample.Issues.Issue11896"
+             xmlns:local="clr-namespace:Maui.Controls.Sample.Issues"
+             x:Name="ThisMainPage"
+             Title="Main Page">
+
+  <Grid RowDefinitions="Auto,*">
+
+    <HorizontalStackLayout
+          Grid.Row="0"
+          Padding="20"
+          HorizontalOptions="Center"
+          Spacing="20">
+      <Button Command="{Binding AddCommand}" Text="Add item" AutomationId="AddButton" />
+      <Button Command="{Binding RemoveCommand}" Text="Remove item" AutomationId="RemoveButton" />
+    </HorizontalStackLayout>
+
+    <CollectionView Grid.Row="1" ItemsSource="{Binding ItemList}">
+
+      <CollectionView.HeaderTemplate>
+        <DataTemplate>
+          <Label
+              Padding="10"
+              FontAttributes="Bold"
+              FontSize="Large"
+              Text="Cities" />
+        </DataTemplate>
+      </CollectionView.HeaderTemplate>
+
+      <CollectionView.ItemTemplate>
+        <DataTemplate>
+          <Label Padding="20,5,5,5" Text="{Binding .}" />
+        </DataTemplate>
+      </CollectionView.ItemTemplate>
+
+      <CollectionView.EmptyViewTemplate>
+        <DataTemplate>
+          <Label Padding="20,5,5,5" Text="Empty" />
+        </DataTemplate>
+      </CollectionView.EmptyViewTemplate>
+
+      <CollectionView.FooterTemplate>
+        <DataTemplate>
+          <Label
+              Padding="10"
+              FontAttributes="Bold"
+              FontSize="Large"
+              Text="Hello world !!!" />
+        </DataTemplate>
+      </CollectionView.FooterTemplate>
+
+    </CollectionView>
+
+  </Grid>
+</ContentPage>

src/Controls/tests/TestCases.Android.Tests/snapshots/android/CollectionviewFooterHideswhenDynamicallyAddorRemoveItems.png

@@ -0,0 +1,74 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+using System.Windows.Input;
+using System.Collections.Specialized;
+
+
+namespace Maui.Controls.Sample.Issues
+{
+	[XamlCompilation(XamlCompilationOptions.Compile)]
+	[Issue(IssueTracker.Github, 11896, "CollectionView Header/Footer/EmptyView issues when adding/removing items", PlatformAffected.Android)]
+	public partial class Issue11896
+	{
+		public Issue11896()
+		{
+			InitializeComponent();
+			BindingContext = new Issue11896ViewModel();
+		}
+	}
+	internal class Issue11896ViewModel
+	{
+		// Define a static list of cities to add to the collection
+		private List<string> _staticCities = new()
+		{
+			"Paris",
+			"New York",
+			"Tokyo",
+			"Berlin",
+			"Madrid",
+			"London"
+		};
+
+		private int _currentIndex = 0;
+
+		public ObservableCollection<string> ItemList { get; set; }
+
+		public ICommand AddCommand => new Command(Add);
+		public ICommand RemoveCommand => new Command(Remove);
+
+		public Issue11896ViewModel()
+		{
+			// Initialize the ItemList
+			ItemList = new ObservableCollection<string>();
+		}
+
+		private void Add()
+		{
+			// Add the next city from the static list
+			if (_currentIndex < _staticCities.Count)
+			{
+				ItemList.Add(_staticCities[_currentIndex]);
+				_currentIndex++;
+			}
+			else
+			{
+				// Optionally reset the index or handle the end of the list as needed
+				_currentIndex = 0;  // Resetting to allow cycling through the list again
+			}
+		}
+
+		private void Remove()
+		{
+			// Remove the last item in the list if any exist
+			if (ItemList.Count > 0)
+			{
+				ItemList.RemoveAt(ItemList.Count - 1);
+				// Decrement the index to ensure the correct city is added next time
+				_currentIndex = Math.Max(0, _currentIndex - 1);
+			}
+		}
+	}
+}

src/Controls/tests/TestCases.HostApp/Issues/Issue11896.xaml

@@ -0,0 +1,41 @@
+#if !MACCATALYST && !WINDOWS
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	internal class Issue11896 : _IssuesUITest
+	{
+		public Issue11896(TestDevice device) : base(device) { }
+
+		public override string Issue => "CollectionView Header/Footer/EmptyView issues when adding/removing items";
+
+		[Test]
+
+		[Category(UITestCategories.CollectionView)]
+		public void CollectionviewFooterHideswhenDynamicallyAddorRemoveItems()
+		{
+			App.WaitForElement("AddButton");
+			App.Tap("AddButton");
+			App.Tap("AddButton");
+			App.Tap("AddButton");
+			// Here we check for Footer proper visibility with proper alignment in view.
+			VerifyScreenshot();
+		}
+
+		[Test]
+		[Category(UITestCategories.CollectionView)]
+		public void CollectionViewHeaderBlankWhenLastItemRemoved()
+		{
+			App.WaitForElement("AddButton");
+			App.Tap("RemoveButton");
+			App.Tap("RemoveButton");
+			App.Tap("RemoveButton");
+			App.Tap("AddButton");
+			// Here we check for Header and Footer proper visibility with proper alignment in view.
+			VerifyScreenshot();
+		}
+	}
+}
+#endif