[iOS] Fixed NRE removing cells on ListView

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue11381.xaml

@@ -0,0 +1,56 @@
+<?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.Issue11381"
+    Title="Issue 11381">
+    <Grid RowDefinitions="Auto,Auto, *">
+        <Label
+            Grid.Row="0"
+            Padding="12"
+            BackgroundColor="Black"
+            TextColor="White"
+            Text="Tap on image with red background to remove a cell. Repeat for all cells. Without crash, the test has passed."/>
+        <Label
+            Grid.Row="1"
+            AutomationId="ResultId"
+            x:Name="ItemsCount"/>
+        <ListView
+            Grid.Row="2"
+            AutomationId="ListViewId" 
+            x:Name="Issue11381ListView"
+            GroupDisplayBinding="{Binding LongName}"
+            GroupShortNameBinding="{Binding ShortName}"
+            HasUnevenRows="True"
+            IsGroupingEnabled="true">
+            <ListView.ItemTemplate>
+                <DataTemplate>
+                    <ViewCell>
+                        <ViewCell.View>
+                            <StackLayout>
+                                <Label
+                                    FontSize="Large"
+                                    Text="{Binding Name}" />
+                                <Label
+                                    Text="{Binding Comment}" />
+                                <Image
+                                    Aspect="AspectFit"
+                                    BackgroundColor="Red"
+                                    HeightRequest="40"
+                                    Source="https://img-prod-cms-rt-microsoft-com.akamaized.net/cms/api/am/imageFileData/RE1Mu3b?ver=5c31" />
+                                <StackLayout.GestureRecognizers>
+                                    <TapGestureRecognizer
+                                        Tapped="OnTapGestureRecognizerTapped" />
+                                </StackLayout.GestureRecognizers>
+                            </StackLayout>
+                        </ViewCell.View>
+                    </ViewCell>
+                </DataTemplate>
+            </ListView.ItemTemplate>
+        </ListView>
+    </Grid>
+</controls:TestContentPage>

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue11381.xaml.cs

@@ -0,0 +1,112 @@
+using System;
+using System.Collections.ObjectModel;
+using System.Threading.Tasks;
+using System.Windows.Input;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+using System.Linq;
+
+#if UITEST
+using Xamarin.Forms.Core.UITests;
+using Xamarin.UITest;
+using NUnit.Framework;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+#if UITEST
+	[Category(UITestCategories.ListView)]
+#endif
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 11381, "[Bug] [iOS] NRE on grouped ListView when removing cells with gesture recognizers",
+		PlatformAffected.iOS)]
+	public partial class Issue11381 : TestContentPage
+	{
+		public Issue11381()
+		{
+#if APP
+			InitializeComponent();
+
+			grouped = new ObservableCollection<GroupedIssue11381Model> ();
+
+			var g1Group = new GroupedIssue11381Model () { LongName = "Group1", ShortName="g1" };
+			var g2Group = new GroupedIssue11381Model () { LongName = "Group2", ShortName = "g2" };
+
+			g1Group.Add (new Issue11381Model () { Name = "G1I1", IsReallyAVeggie = true, Comment = "Lorem ipsum dolor sit amet" });
+			g1Group.Add (new Issue11381Model () { Name = "G1I2", IsReallyAVeggie = false, Comment = "Lorem ipsum dolor sit amet" });
+			g1Group.Add (new Issue11381Model () { Name = "G1I3", IsReallyAVeggie = true, Comment = "Lorem ipsum dolor sit amet" });
+			g1Group.Add (new Issue11381Model () { Name = "G1I4", IsReallyAVeggie = true, Comment = "Lorem ipsum dolor sit amet" });
+
+			g2Group.Add (new Issue11381Model () {Name = "G2I1", IsReallyAVeggie = false,Comment = "Lorem ipsum dolor sit amet" });
+			g2Group.Add (new Issue11381Model () {Name = "G2I2", IsReallyAVeggie = false,Comment = "Lorem ipsum dolor sit amet" });
+
+			grouped.Add (g1Group); grouped.Add (g2Group);
+
+			Issue11381ListView.ItemsSource = grouped;
+#endif
+		}
+
+		public ObservableCollection<GroupedIssue11381Model> grouped { get; set; }
+
+		protected override void Init()
+		{
+
+		}
+
+#if APP
+		void OnTapGestureRecognizerTapped(object sender, EventArgs e)
+		{
+			if (sender is View view && view.BindingContext is Issue11381Model model)
+			{
+				var group = grouped.FirstOrDefault(g => g.Contains(model));
+
+				if (group != null)
+				{
+					group.Remove(model);
+
+					if (!group.Any())
+					{
+						grouped.Remove(group);
+					}
+
+					ItemsCount.Text = $"{grouped.Count} groups";
+				}
+			}
+		}
+#endif
+
+#if UITEST
+		[Test]
+		public void Issue11381RemoveListViewGroups()
+		{
+			RunningApp.WaitForElement("ListViewId", "Timed out waiting for the ListView.");
+
+			RunningApp.Tap(x => x.Marked("G1I1"));
+			RunningApp.Tap(x => x.Marked("G1I2"));
+			RunningApp.Tap(x => x.Marked("G1I3"));
+			RunningApp.Tap(x => x.Marked("G1I4"));
+			RunningApp.Tap(x => x.Marked("G2I1"));
+			RunningApp.Tap(x => x.Marked("G2I2"));
+
+			RunningApp.WaitForElement("ResultId");
+			Assert.AreEqual("0 groups", RunningApp.WaitForElement("ResultId")[0].ReadText());
+		}
+#endif
+	}
+
+	[Preserve(AllMembers = true)]
+	public class Issue11381Model
+	{
+		public string Name { get; set; }
+		public string Comment { get; set; }
+		public bool IsReallyAVeggie { get; set; }
+		public string Image { get; set; }
+	}
+
+	[Preserve(AllMembers = true)]
+	public class GroupedIssue11381Model : ObservableCollection<Issue11381Model>
+	{
+		public string LongName { get; set; }
+		public string ShortName { get; set; }
+	}
+}

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

@@ -1655,6 +1655,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Issue8988.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue12084.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue12512.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue11381.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue12685.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue12642.cs" />
   </ItemGroup>
@@ -2005,6 +2006,9 @@
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue12084.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue11381.xaml">
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Bugzilla27417Xaml.xaml">

Xamarin.Forms.Platform.iOS/EventTracker.cs

@@ -594,7 +594,7 @@ void LoadRecognizers()
 					continue;
 
 				var nativeRecognizer = GetNativeRecognizer(recognizer);
-				if (nativeRecognizer != null)
+				if (nativeRecognizer != null && _handler != null)
 				{
 #if __MOBILE__
 					nativeRecognizer.ShouldReceiveTouch = _shouldReceiveTouch;