[iOS,Android] Fix gap when setting Separator None and recycle element and on Android when using grouping (#949)

* [Controls] Add repo for bugzilla 39802

* [iOS] Make ContextCell hide the gap when we aren't using a separator

* [Controls] Update test

* [iOS] Only fix height if separator is hidden.

* [iOS] Only fix if it's a ListiView

* [Android] Fix separator showing when using Grouping

* Update Bugzilla39802.cs

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla39802.cs

@@ -0,0 +1,100 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+using System.Collections.ObjectModel;
+using System.Collections.Generic;
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 39802, "Gap between ListView cells even if SeparatorVisablity is set to none ", PlatformAffected.iOS)]
+	public class Bugzilla39802 : TestContentPage // or TestMasterDetailPage, etc ...
+	{
+		protected override void Init()
+		{
+			BackgroundColor = Color.Yellow;
+
+			var list = new ObservableCollection<GroupedData>();
+
+			for (int i = 1; i <= 2; i++)
+			{
+				var group = new GroupedData { GroupName = $"Group #{i}" };
+
+				for (int j = 1; j < 30; j++)
+				{
+					var item = new MyItem { Title = $"Item: #{i}-{j}", Color = (j % 2 == 0) ? Color.Blue : Color.Red };
+
+					group.Add(item);
+				}
+				list.Add(group);
+			}
+
+			ListItems = list;
+
+			BindingContext = this;
+			var lst = new ListView(ListViewCachingStrategy.RecycleElement)
+			{
+				BackgroundColor = Color.Transparent,
+				ItemTemplate = new DataTemplate(typeof(ItemTemplate)),
+				GroupHeaderTemplate = new DataTemplate(typeof(GroupHeaderTemplate)),
+				IsGroupingEnabled = true,
+				GroupDisplayBinding = new Binding(nameof(GroupedData.GroupName)),
+				GroupShortNameBinding = new Binding(nameof(GroupedData.GroupName)),
+			};
+			lst.SeparatorVisibility = SeparatorVisibility.None;
+			lst.SeparatorColor = Color.Green;
+			lst.SetBinding(ListView.ItemsSourceProperty, nameof(ListItems));
+			Content = lst;
+		}
+
+		public class ItemTemplate : ViewCell
+		{
+			public ItemTemplate()
+			{
+				var stk = new StackLayout
+				{
+					Padding = new Thickness(15, 0, 0, 0)
+				};
+				stk.SetBinding(VisualElement.BackgroundColorProperty, nameof(MyItem.Color));
+				var lbl = new Label
+				{
+					TextColor = Color.Yellow,
+					VerticalOptions = LayoutOptions.CenterAndExpand
+				};
+				lbl.SetBinding(Label.TextProperty, nameof(MyItem.Title));
+				stk.Children.Add(lbl);
+				View = stk;
+			}
+		}
+		public class GroupHeaderTemplate : ViewCell
+		{
+			public GroupHeaderTemplate()
+			{
+				var title = new Label { TextColor = Color.White, FontSize = 16 };
+				title.SetBinding(Label.TextProperty, new Binding(nameof(GroupedData.GroupName), BindingMode.OneWay));
+
+				View = new StackLayout
+				{
+					Padding = new Thickness(8, 0),
+					VerticalOptions = LayoutOptions.StartAndExpand,
+					BackgroundColor = Color.Pink,
+					Orientation = StackOrientation.Horizontal,
+					Children = { title },
+				};
+			}
+		}
+
+		public ObservableCollection<GroupedData> ListItems { get; set; }
+		public class MyItem
+		{
+			public string Title { get; set; }
+
+			public Color Color { get; set; }
+		}
+
+		[Preserve(AllMembers = true)]
+		public class GroupedData : List<MyItem>
+		{
+			public string GroupName { get; set; }
+		}
+	}
+}

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

@@ -291,6 +291,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)ListViewNRE.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla55745.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla55365.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla39802.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla53179.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla54036.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla40161.cs" />

Xamarin.Forms.Platform.Android/Renderers/ListViewAdapter.cs

@@ -541,7 +541,8 @@ namespace Xamarin.Forms.Platform.Android
 			bline = null;
 			if (cellIsBeingReused)
 				return;
-			var makeBline = _listView.SeparatorVisibility == SeparatorVisibility.Default || isHeader && !nextCellIsHeader;
+			bool isSeparatorVisible = _listView.SeparatorVisibility == SeparatorVisibility.Default;
+			var makeBline = isSeparatorVisible || isHeader && isSeparatorVisible && !nextCellIsHeader;
 			if (makeBline)
 			{
 				bline = new AView(_context) { LayoutParameters = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MatchParent, 1) };

Xamarin.Forms.Platform.iOS/ContextActionCell.cs

@@ -127,7 +127,7 @@ namespace Xamarin.Forms.Platform.iOS
 				((INotifyCollectionChanged)cell.ContextActions).CollectionChanged += OnContextItemsChanged;
 			}
 
-			var height = Frame.Height;
+			var height = Frame.Height + (parentListView != null && parentListView.SeparatorVisibility == SeparatorVisibility.None ? 0.5f : 0f);
 			var width = ContentView.Frame.Width;
 
 			nativeCell.Frame = new RectangleF(0, 0, width, height);