[iOS] - Fixed the performance issue that occurred when updating the Spacing in CollectionView for both Vertical List and Grid layouts

src/Controls/src/Core/Handlers/Items2/CollectionViewHandler2.iOS.cs

@@ -1,6 +1,7 @@
 #nullable disable
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Text;
 using Foundation;
 using Microsoft.Maui.Handlers;
@@ -203,20 +204,29 @@ void SubscribeToItemsLayoutPropertyChanged(IItemsLayout itemsLayout)
 		{
 			if (itemsLayout is not null)
 			{
-				itemsLayout.PropertyChanged += (sender, args) =>
-				{
-					if (args.PropertyName == nameof(ItemsLayout.SnapPointsAlignment) ||
-						args.PropertyName == nameof(ItemsLayout.SnapPointsType) ||
-						args.PropertyName == nameof(GridItemsLayout.VerticalItemSpacing) ||
-						args.PropertyName == nameof(GridItemsLayout.HorizontalItemSpacing) ||
-						args.PropertyName == nameof(GridItemsLayout.Span) ||
-						args.PropertyName == nameof(LinearItemsLayout.ItemSpacing))
-
-					{
-						UpdateLayout();
-					}
-				};
+				itemsLayout.PropertyChanged -= ItemsLayoutPropertyChanged;
+				itemsLayout.PropertyChanged += ItemsLayoutPropertyChanged;
+			}
+		}
+
+		void ItemsLayoutPropertyChanged(object sender, PropertyChangedEventArgs e)
+		{
+			if (e.PropertyName == nameof(ItemsLayout.SnapPointsAlignment) ||
+				e.PropertyName == nameof(ItemsLayout.SnapPointsType) ||
+				e.PropertyName == nameof(GridItemsLayout.VerticalItemSpacing) ||
+				e.PropertyName == nameof(GridItemsLayout.HorizontalItemSpacing) ||
+				e.PropertyName == nameof(GridItemsLayout.Span) ||
+				e.PropertyName == nameof(LinearItemsLayout.ItemSpacing))
+
+			{
+				UpdateLayout();
 			}
 		}
+
+		protected override void DisconnectHandler(UIView platformView)
+		{
+			ItemsView.ItemsLayout.PropertyChanged -= ItemsLayoutPropertyChanged;
+			base.DisconnectHandler(platformView);
+		}
 	}
 }

src/Controls/src/Core/PublicAPI/net-ios/PublicAPI.Unshipped.txt

@@ -14,4 +14,5 @@ virtual Microsoft.Maui.Controls.BindableProperty.CreateDefaultValueDelegate<TDec
 ~virtual Microsoft.Maui.Controls.BindableProperty.ValidateValueDelegate<TPropertyType>.Invoke(Microsoft.Maui.Controls.BindableObject bindable, TPropertyType value) -> bool
 ~virtual Microsoft.Maui.Controls.CollectionSynchronizationCallback.Invoke(System.Collections.IEnumerable collection, object context, System.Action accessMethod, bool writeAccess) -> void
 ~virtual Microsoft.Maui.Controls.Internals.EvaluateJavaScriptDelegate.Invoke(string script) -> System.Threading.Tasks.Task<string>
-~virtual Microsoft.Maui.Controls.PropertyChangingEventHandler.Invoke(object sender, Microsoft.Maui.Controls.PropertyChangingEventArgs e) -> void
+~virtual Microsoft.Maui.Controls.PropertyChangingEventHandler.Invoke(object sender, Microsoft.Maui.Controls.PropertyChangingEventArgs e) -> void
+~override Microsoft.Maui.Controls.Handlers.Items2.CollectionViewHandler2.DisconnectHandler(UIKit.UIView platformView) -> void

src/Controls/src/Core/PublicAPI/net-maccatalyst/PublicAPI.Unshipped.txt

@@ -14,4 +14,5 @@ virtual Microsoft.Maui.Controls.BindableProperty.CreateDefaultValueDelegate<TDec
 ~virtual Microsoft.Maui.Controls.BindableProperty.ValidateValueDelegate<TPropertyType>.Invoke(Microsoft.Maui.Controls.BindableObject bindable, TPropertyType value) -> bool
 ~virtual Microsoft.Maui.Controls.CollectionSynchronizationCallback.Invoke(System.Collections.IEnumerable collection, object context, System.Action accessMethod, bool writeAccess) -> void
 ~virtual Microsoft.Maui.Controls.Internals.EvaluateJavaScriptDelegate.Invoke(string script) -> System.Threading.Tasks.Task<string>
-~virtual Microsoft.Maui.Controls.PropertyChangingEventHandler.Invoke(object sender, Microsoft.Maui.Controls.PropertyChangingEventArgs e) -> void
+~virtual Microsoft.Maui.Controls.PropertyChangingEventHandler.Invoke(object sender, Microsoft.Maui.Controls.PropertyChangingEventArgs e) -> void
+~override Microsoft.Maui.Controls.Handlers.Items2.CollectionViewHandler2.DisconnectHandler(UIKit.UIView platformView) -> void

src/Controls/tests/TestCases.HostApp/Issues/Issue27666.cs

@@ -0,0 +1,56 @@
+using System.Collections.ObjectModel;
+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 27666, "Vertical list and Vertical grid pages have different abnormal behaviors when clicking Update after changing the spacing value", PlatformAffected.iOS | PlatformAffected.macOS)]
+
+public class Issue27666_NavigationPage : TestNavigationPage
+{
+	protected override void Init()
+	{
+		var root = CreateRootContentPage();
+		PushAsync(root);
+	}
+
+	ContentPage CreateRootContentPage()
+	{
+		ContentPage ContentPage = new ContentPage();
+
+		VerticalStackLayout rootLayout = new VerticalStackLayout
+		{
+			Spacing = 10,
+			Padding = new Thickness(10),
+		};
+
+		Button collectionViewButton = new Button
+		{
+			Text = "Navigate to VerticalList CollectionView",
+			AutomationId = "NavigationButton"
+		};
+		collectionViewButton.Clicked += (s, e) => Navigation.PushAsync(new Issue27666());
+
+		rootLayout.Add(collectionViewButton);
+		ContentPage.Content = rootLayout;
+		return ContentPage;
+	}
+}
+
+public partial class Issue27666 : ContentPage
+{
+	ObservableCollection<string> items;
+
+	public Issue27666()
+	{
+		InitializeComponent();
+		items = new ObservableCollection<string>(Enumerable.Range(1, 30).Select(i => $"Item {i}"));
+		collectionView.ItemsSource = items;
+	}
+
+	private void OnItemSpacingButtonClicked(object sender, EventArgs e)
+	{
+		if (collectionView.ItemsLayout is LinearItemsLayout layout)
+		{
+			layout.ItemSpacing = layout.ItemSpacing == 0 ? 50 : 20;
+		}
+	}
+}

src/Controls/tests/TestCases.HostApp/Issues/Issue27666.xaml

@@ -0,0 +1,32 @@
+<?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.Issue27666">
+
+  <Grid RowSpacing="5">
+    <Grid.RowDefinitions>
+      <RowDefinition Height="Auto"/>
+      <RowDefinition Height="*"/>
+    </Grid.RowDefinitions>
+
+    <Button Grid.Row="0"
+            Text="Update ItemSpacing"
+            AutomationId="UpdateItemSpacingButton"
+            Clicked="OnItemSpacingButtonClicked"/>
+
+    <CollectionView x:Name="collectionView"
+                    Grid.Row="1"
+                    AutomationId="ItemsLayoutCollectionView"
+                    ItemsLayout="HorizontalList">
+      <CollectionView.ItemTemplate>
+        <DataTemplate>
+          <Border Padding="10"
+              Margin="5"
+              BackgroundColor="LightGray">
+            <Label Text="{Binding .}"/>
+          </Border>
+        </DataTemplate>
+      </CollectionView.ItemTemplate>
+    </CollectionView>
+  </Grid>
+</ContentPage>

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue27666.cs

@@ -0,0 +1,30 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue27666 : _IssuesUITest
+{
+	public override string Issue => "Vertical list and Vertical grid pages have different abnormal behaviors when clicking Update after changing the spacing value";
+	const string UpdateItemSpacingButton = "UpdateItemSpacingButton";
+	const string ItemsLayoutCollectionView = "ItemsLayoutCollectionView";
+	const string NavigationButton = "NavigationButton";
+	public Issue27666(TestDevice device) : base(device) { }
+
+	[Test]
+	[Category(UITestCategories.CollectionView)]
+	public void VerifySpacingUpdateInItemsLayout()
+	{
+		App.WaitForElement(NavigationButton);
+		App.Tap(NavigationButton);
+		App.WaitForElement(ItemsLayoutCollectionView);
+		App.Tap(UpdateItemSpacingButton);
+		App.TapBackArrow();
+		App.WaitForElement(NavigationButton);
+		App.Tap(NavigationButton);
+		App.WaitForElement(ItemsLayoutCollectionView);
+		App.Tap(UpdateItemSpacingButton);
+		App.WaitForElement(ItemsLayoutCollectionView);
+	}
+}