[Android] Always create a new cell for GroupHeader when using Recycling (#206)

* [Android] Always create a new cell for GroupHeader when using RecycleElement

* [iOS] Fix uitest iOS

* [Android] Fix test on android

3 files changed, 246 insertions, 1 deletions

diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla40704.cs b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla40704.cs
new file mode 100644
index 00000000..dcae4617
--- /dev/null
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla40704.cs
@@ -0,0 +1,231 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+using System.Text;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+#endif
+
+namespace Xamarin.Forms.Controls
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 40704, "Strange duplication of listview headers when collapsing/expanding sections")]
+	public class Bugzilla40704 : TestContentPage // or TestMasterDetailPage, etc ...
+	{
+		ListView listview;
+		int count = 2;
+
+		protected override void Init()
+		{
+			listview = new ListView(ListViewCachingStrategy.RecycleElement)
+			{
+				AutomationId = "lstMain",
+				IsGroupingEnabled = true,
+				HasUnevenRows = true,
+				GroupHeaderTemplate = new DataTemplate(typeof(GroupHeaderViewCell)),
+				ItemTemplate = new DataTemplate(typeof(ItemTestViewCell))
+			};
+
+			FillPatientsList();
+
+			var button = new Button()
+			{
+				Text = "Collapse",
+				AutomationId = "btnCollappse"
+			};
+			listview.Footer = button;
+			button.Clicked += Button_Clicked;
+			Content = listview;
+		}
+
+		void Button_Clicked(object sender, EventArgs e)
+		{
+			var source = listview.ItemsSource as List<PatientsGroupViewModel>;
+			source[count].Toggle();
+			count--;
+			if (count < 0)
+				count = 2;
+		}
+
+		private void FillPatientsList()
+		{
+			const int groupsNumber = 3;
+			const int patientsNumber = 10;
+
+			var patientGroups = new List<PatientsGroupViewModel>();
+			var random = new Random();
+
+			for (var i = 0; i < groupsNumber; i++)
+			{
+				var patients = new List<PatientViewModel>();
+				for (var j = 0; j < patientsNumber; j++)
+				{
+					var code = string.Format("{0}-{1}", i, j);
+					var length = random.Next(5, 100);
+					var strBuilder = new StringBuilder();
+					for (int z = 0; z < length; z++)
+					{
+						strBuilder.Append(code);
+						if (z % 7 == 0)
+						{
+							strBuilder.Append(' ');
+						}
+					}
+
+					patients.Add(new PatientViewModel(code) { Description = strBuilder.ToString() });
+				}
+
+				patientGroups.Add(new PatientsGroupViewModel(patients)
+				{
+					Title = "Menu - " + i.ToString()
+				});
+
+			}
+
+			listview.ItemsSource = patientGroups;
+		}
+
+		[Preserve(AllMembers = true)]
+		public class GroupHeaderViewCell : ViewCell
+		{
+			TapGestureRecognizer tapGesture;
+
+			public GroupHeaderViewCell()
+			{
+				Height = 40;
+				var grd = new Grid { BackgroundColor = Color.Aqua, Padding = new Thickness(5, 10) };
+				tapGesture = new TapGestureRecognizer();
+				tapGesture.Tapped += HeaderCell_OnTapped;
+				grd.GestureRecognizers.Add(tapGesture);
+				var lbl = new Label { HorizontalOptions = LayoutOptions.FillAndExpand, TextColor = Color.Black, FontSize = 16 };
+				lbl.SetBinding(Label.TextProperty, new Binding("Title"));
+
+				grd.Children.Add(lbl);
+				View = grd;
+			}
+
+			void HeaderCell_OnTapped(object sender, EventArgs e)
+			{
+				var cell = (Layout)sender;
+				var vm = cell.BindingContext as PatientsGroupViewModel;
+
+				if (vm != null)
+				{
+					vm.Toggle();
+				}
+			}
+		}
+
+		[Preserve(AllMembers = true)]
+		public class ItemTestViewCell : ViewCell
+		{
+			public ItemTestViewCell()
+			{
+
+				var grd = new Grid { BackgroundColor = Color.Yellow };
+				var lbl = new Label { HorizontalOptions = LayoutOptions.FillAndExpand, TextColor = Color.Black, FontSize = 16, LineBreakMode = LineBreakMode.WordWrap };
+				lbl.SetBinding(Label.TextProperty, new Binding("Description"));
+				grd.Children.Add(lbl);
+				View = grd;
+			}
+		}
+
+		[Preserve(AllMembers = true)]
+		public class RangeObservableCollection<T> : ObservableCollection<T>
+		{
+			private bool _suppressNotification = false;
+
+			protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
+			{
+				if (!_suppressNotification)
+					base.OnCollectionChanged(e);
+			}
+
+			public void AddRange(IEnumerable<T> list)
+			{
+				if (list == null)
+					throw new ArgumentNullException("list");
+
+				_suppressNotification = true;
+
+				foreach (var item in list)
+				{
+					Add(item);
+				}
+				_suppressNotification = false;
+				OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+			}
+		}
+
+		[Preserve(AllMembers = true)]
+		public class PatientsGroupViewModel : RangeObservableCollection<PatientViewModel>
+		{
+			public bool IsCollapsed { get; private set; }
+
+			public string Title { get; set; }
+
+			private readonly List<PatientViewModel> _patients;
+
+			public PatientsGroupViewModel(List<PatientViewModel> patients)
+			{
+				_patients = patients;
+
+				UpdateCollection();
+			}
+
+			public void Toggle()
+			{
+				IsCollapsed = !IsCollapsed;
+
+				UpdateCollection();
+			}
+
+			private void UpdateCollection()
+			{
+				if (!IsCollapsed)
+				{
+					AddRange(_patients);
+				}
+				else
+				{
+					Clear();
+				}
+			}
+		}
+
+		[Preserve(AllMembers = true)]
+		public class PatientViewModel
+		{
+			public PatientViewModel(string code)
+			{
+				Code = code;
+			}
+
+			public string Code { get; set; }
+
+			public string Description { get; set; }
+		}
+
+
+		#if UITEST
+		[Test]
+		public void Bugzilla40704Test()
+		{
+			RunningApp.ScrollDownTo("btnCollappse", "lstMain", ScrollStrategy.Gesture, 0.8, timeout: TimeSpan.FromMinutes(2));
+			RunningApp.Tap("btnCollappse");
+			RunningApp.ScrollDownTo("btnCollappse", "lstMain", ScrollStrategy.Gesture, 0.8, timeout: TimeSpan.FromMinutes(2));
+			RunningApp.Tap("btnCollappse");
+			RunningApp.ScrollDownTo("btnCollappse", "lstMain", ScrollStrategy.Gesture, 0.8, timeout: TimeSpan.FromMinutes(2));
+			RunningApp.Tap("btnCollappse");
+			RunningApp.WaitForElement("Menu - 2");
+			RunningApp.WaitForElement("Menu - 1");
+			RunningApp.WaitForElement("Menu - 0");
+		}
+#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 991270b6..00fad875 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
@@ -403,6 +403,7 @@
     </Compile>
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla39963.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla39987.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla40704.cs" />
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Bugzilla22229.xaml">
diff --git a/Xamarin.Forms.Platform.Android/Renderers/ListViewAdapter.cs b/Xamarin.Forms.Platform.Android/Renderers/ListViewAdapter.cs
index 81214957..522ff4b2 100644
--- a/Xamarin.Forms.Platform.Android/Renderers/ListViewAdapter.cs
+++ b/Xamarin.Forms.Platform.Android/Renderers/ListViewAdapter.cs
@@ -421,7 +421,20 @@ namespace Xamarin.Forms.Platform.Android
 
 				if (global == position || cells.Count > 0)
 				{
-					cells.Add(group.HeaderContent);
+					if (_listView.CachingStrategy == ListViewCachingStrategy.RecycleElement)
+					{
+						var groupContent = _listView.TemplatedItems.GroupHeaderTemplate.CreateContent(group.ItemsSource, _listView) as Cell;
+						if (groupContent != null)
+						{
+							groupContent.BindingContext = group.ItemsSource;
+							cells.Add(groupContent);
+						}
+					}
+					else
+					{
+						cells.Add(group.HeaderContent);
+					}
+
 					if (cells.Count == take)
 						return cells;
 				}