[Android] Fix NRE When Scrolling ListView and Item With Context Actions Is Selected (#310)

* Fix NRE When Item With Context Actions Selected

* Add UITest

2 files changed, 69 insertions, 0 deletions

diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla42832.cs b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla42832.cs
new file mode 100644
index 00000000..77b98df7
--- /dev/null
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla42832.cs
@@ -0,0 +1,68 @@
+using System;
+using System.Collections.Generic;
+using Xamarin.Forms.Internals;
+using Xamarin.Forms.CustomAttributes;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+    [Preserve(AllMembers = true)]
+    [Issue(IssueTracker.Bugzilla, 42832, "Scrolling a ListView with active ContextAction Items causes NRE", PlatformAffected.Android)]
+    public class Bugzilla42832 : TestContentPage
+	{
+        ListView listview;
+
+        protected override void Init()
+        {
+            var items = new List<string>();
+            for(int i=0; i<20; i++)
+                items.Add($"Item #{i}");
+
+            var template = new DataTemplate(typeof(TestCell));
+            template.SetBinding(TextCell.TextProperty, ".");
+
+            listview = new ListView(ListViewCachingStrategy.RetainElement)
+            {
+                AutomationId = "mainList",
+                ItemsSource = items,
+                ItemTemplate = template
+            };
+
+            Content = listview;
+        }
+
+        [Preserve(AllMembers = true)]
+        public class TestCell : TextCell
+        {
+            public TestCell()
+            {
+                var menuItem = new MenuItem { Text = "Test Item" };
+                ContextActions.Add(menuItem);
+            }
+        }
+
+#if UITEST
+        [Test]
+        public void ContextActionsScrollNRE()
+        {
+            // mark is an icon on android
+            RunningApp.TouchAndHold(q => q.Marked("Item #0"));
+            RunningApp.WaitForElement(q => q.Marked("Test Item"));
+
+            int counter = 0;
+            while(counter < 5)
+            {
+                RunningApp.ScrollDownTo("Item #15", "mainList", ScrollStrategy.Gesture, timeout:TimeSpan.FromMinutes(1));
+                RunningApp.ScrollUpTo("Item #0", "mainList", ScrollStrategy.Gesture, timeout: TimeSpan.FromMinutes(1));
+                counter++;
+            }
+
+            RunningApp.Screenshot("If the app did not crash, then the test has passed.");
+        }
+#endif
+    }
+}
diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
index 224ef47a..debaecca 100644
--- a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
@@ -128,6 +128,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla43516.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla44166.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla44461.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla42832.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)CarouselAsync.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla34561.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla34727.cs" />