[iOS] Fix issue disposing the EmptyView

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue12374.xaml

@@ -0,0 +1,87 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<controls:TestContentPage
+    xmlns="http://xamarin.com/schemas/2014/forms"
+    xmlns:controls="clr-namespace:Xamarin.Forms.Controls"
+    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.Issues.Issue12374"
+    Title="Issue 12374">
+    <Grid RowDefinitions="Auto,Auto,*">
+        <Label
+            Grid.Row="0"
+            AutomationId = "TestReady"
+            Padding="12"
+            BackgroundColor="Black"
+            TextColor="White"
+            Text="Tap each item to remove them and view the EmptyView. Then, tap the AddItems button. Without crash, the test has passed."/>
+        <StackLayout
+            Grid.Row="1"
+            Orientation="Horizontal"
+            HorizontalOptions="Center"
+            Margin="20">
+            <Button
+                AutomationId="AddItems"
+                Text="Add Items"
+                Clicked="AddItemsButton_Clicked" />
+            <Button
+                AutomationId="RemoveItems"
+                Text="Remove Items"
+                Clicked="RemoveItemsButton_Clicked" />
+        </StackLayout>
+        <RefreshView
+            Grid.Row="2"
+            x:Name="MainRefreshView"
+            IsRefreshing="{Binding IsRefreshing}"
+            Command="{Binding RefreshCommand}">
+            <CollectionView
+                Grid.Row="1"
+                ItemsSource="{Binding Items}"
+                SelectionMode="Single"
+                SelectionChanged="CollectionView_SelectionChanged">
+                <CollectionView.EmptyView>
+                    <Grid>
+                        <Label
+                            Text="Empty View"
+                            HorizontalOptions="Center"
+                            VerticalOptions="Center" />
+                    </Grid>
+                </CollectionView.EmptyView>
+                <!--
+                <CollectionView.EmptyViewTemplate>
+                    <DataTemplate>
+                        <Grid>
+                            <Label Text="Empty Template View" HorizontalOptions="Center" VerticalOptions="Center" />
+                        </Grid>
+                    </DataTemplate>
+                </CollectionView.EmptyViewTemplate>
+                -->
+                <CollectionView.ItemTemplate>
+                    <DataTemplate>
+                        <!--
+                        <SwipeView>
+                            <SwipeView.RightItems>
+                                <SwipeItems>
+                                    <SwipeItem Text="Delete" BackgroundColor="Red" Invoked="Item_SwipeInvoked" />
+                                </SwipeItems>
+                            </SwipeView.RightItems>
+                            <Grid HeightRequest="40" Padding="10" BackgroundColor="{Binding Color}">
+                                <Label Text="{Binding Name}" VerticalOptions="Center" />
+                            </Grid>
+                        </SwipeView>
+                        -->
+                        <Grid
+                            HeightRequest="40"
+                            Padding="10"
+                            BackgroundColor="{Binding Color}">
+                            <Label
+                                Text="{Binding Name}"
+                                VerticalOptions="Center" />
+                        </Grid>
+                    </DataTemplate>
+                </CollectionView.ItemTemplate>
+            </CollectionView>
+        </RefreshView>
+    </Grid>
+</controls:TestContentPage>

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue12374.xaml.cs

@@ -0,0 +1,140 @@
+using System;
+using System.Collections.ObjectModel;
+using System.Threading.Tasks;
+using System.Windows.Input;
+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, 12374, "[Bug] [iOS] CollectionView EmptyView causes the application to crash",
+		PlatformAffected.iOS)]
+	public partial class Issue12374 : TestContentPage
+    {
+        int _itemNumber = 0;
+        bool _isRefreshing;
+
+        public Issue12374()
+		{
+#if APP
+			InitializeComponent();
+
+            AddItems();
+
+            BindingContext = this;
+#endif
+        }
+
+		protected override void Init()
+		{
+
+		}
+
+        public bool IsRefreshing
+        {
+            get { return _isRefreshing; }
+            set
+            {
+                _isRefreshing = value;
+                OnPropertyChanged();
+            }
+        }
+
+        public ObservableCollection<Issue12374Model> Items { get; private set; } = new ObservableCollection<Issue12374Model>();
+
+        public ICommand RefreshCommand => new Command(async () => await RefreshItemsAsync());
+
+        async Task RefreshItemsAsync()
+        {
+            IsRefreshing = true;
+            await Task.Delay(TimeSpan.FromSeconds(1));
+            AddItems();
+            IsRefreshing = false;
+        }
+
+        void AddItems()
+        {
+            var random = new Random();
+            for (int i = 0; i < 2; i++)
+            {
+                Items.Add(new Issue12374Model()
+                {
+                    Guid = Guid.NewGuid(),
+                    Color = Color.FromRgb(random.Next(0, 255), random.Next(0, 255), random.Next(0, 255)),
+                    Name = $"Item {_itemNumber++}"
+                });
+            }
+        }
+
+#if APP
+        public void Item_SwipeInvoked(object sender, EventArgs e)
+        {
+            if (sender is SwipeItem swipeItem && swipeItem.BindingContext is Issue12374Model item)
+            {
+                Items.Remove(item);
+            }
+        }
+
+        void AddItemsButton_Clicked(object sender, EventArgs e)
+        {
+            AddItems();
+        }
+
+        void RemoveItemsButton_Clicked(object sender, EventArgs e)
+        {
+            Items.Clear();
+        }
+
+        void CollectionView_SelectionChanged(object sender, SelectionChangedEventArgs e)
+        {
+            if (e.CurrentSelection.Count == 0)
+                return;
+
+            if (sender is CollectionView collectionView)
+            {
+                collectionView.SelectedItems = null;
+            }
+
+            if (e.CurrentSelection[0] is Issue12374Model item)
+            {
+                Items.Remove(item);
+            }
+        }
+#endif
+
+#if UITEST 
+        [Test]
+        public void Issue12374Test()
+        {
+            RunningApp.WaitForElement("TestReady");
+            RunningApp.Tap("RemoveItems");
+  		    RunningApp.Tap("AddItems");
+            RunningApp.Tap("RemoveItems");
+            RunningApp.Screenshot("CollectionViewWithEmptyView");
+        }
+#endif
+    }
+
+    [Preserve(AllMembers = true)]
+    public class Issue12374Model : IEquatable<Issue12374Model>
+    {
+        public Guid Guid { get; set; }
+        public string Name { get; set; }
+        public Color Color { get; set; }
+
+        public bool Equals(Issue12374Model other)
+        {
+            return other.Guid.Equals(Guid);
+        }
+    }
+}

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

@@ -1624,6 +1624,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Issue11081.xaml.cs">
       <DependentUpon>Issue11081.xaml</DependentUpon>
     </Compile>
+    <Compile Include="$(MSBuildThisFileDirectory)Issue12374.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue12222.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue11911.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue11691.xaml.cs" />
@@ -1954,6 +1955,9 @@
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue11081.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue12374.xaml">
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue11911.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>

Xamarin.Forms.Platform.iOS/CollectionView/ItemsViewController.cs

@@ -289,15 +289,20 @@ internal void UpdateEmptyView()
 		protected virtual CGRect DetermineEmptyViewFrame() 
 		{
 			return new CGRect(CollectionView.Frame.X, CollectionView.Frame.Y,
-					CollectionView.Frame.Width, CollectionView.Frame.Height);
+				CollectionView.Frame.Width, CollectionView.Frame.Height);
 		}
 
 		void LayoutEmptyView()
 		{
-			var frame = DetermineEmptyViewFrame();	
+			if (_emptyUIView == null)
+			{
+				UpdateEmptyView();
+				return;
+			}
+
+			var frame = DetermineEmptyViewFrame();
 
-			if (_emptyUIView != null)
-				_emptyUIView.Frame = frame;
+			_emptyUIView.Frame = frame;
 
 			if (_emptyViewFormsElement != null && ItemsView.LogicalChildren.Contains(_emptyViewFormsElement))
 				_emptyViewFormsElement.Layout(frame.ToRectangle());
@@ -387,6 +392,9 @@ void UpdateEmptyViewVisibility(bool isEmpty)
 				if (_emptyViewDisplayed)
 				{
 					_emptyUIView.RemoveFromSuperview();
+					_emptyUIView.Dispose();
+					_emptyUIView = null;
+
 					ItemsView.RemoveLogicalChild(_emptyViewFormsElement);
 				}