[iOS] Fixes for RefreshControl with iOS11 LargeTitles (#1984) fixes #1950

* [Controls] Add repo for #1905

* [iOS] Update refresh control to handle large titles

* [iOS] Update refresh control to handle large titles

[iOS] Update refresh control to handle large titles

[iOS] Delay setting refreshcontrol hidden to true

[iOS] Better fix, manually animate

Fix animation not showing

fix

* [iOS] Update refresh control to handle large titles

* [iOS] Be safe on UIRefreshcontrol changes

* [iOS] Force the Refresh to show when using large titles

* [iOS] Just trigger if we really pull to refresh

* [iOS] More fixes to refreshcontrol

* [iOS] Only force scroll if in Portrait and large titles

* Update ListViewRenderer.cs

Xamarin.Forms.Platform.iOS/Extensions/ViewExtensions.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 
 namespace Xamarin.Forms.Platform.iOS
 {
@@ -16,5 +17,24 @@ namespace Xamarin.Forms.Platform.iOS
 
 			return result;
 		}
+
+		internal static T FindParentOfType<T>(this VisualElement element)
+		{
+			var navPage = element.GetParentsPath()
+										.OfType<T>()
+										.FirstOrDefault();
+			return navPage;
+		}
+
+		internal static IEnumerable<Element> GetParentsPath(this VisualElement self)
+		{
+			Element current = self;
+
+			while (!Application.IsApplicationOrNull(current.RealParent))
+			{
+				current = current.RealParent;
+				yield return current;
+			}
+		}
 	}
 }

Xamarin.Forms.Platform.iOS/Renderers/ListViewRenderer.cs

@@ -33,6 +33,7 @@ namespace Xamarin.Forms.Platform.iOS
 		ITemplatedItemsView<Cell> TemplatedItemsView => Element;
 		public override UIViewController ViewController => _tableViewController;
 		bool _disposed;
+		bool _usingLargeTitles;
 
 		protected UITableViewRowAnimation InsertRowsAnimation { get; set; } = UITableViewRowAnimation.Automatic;
 		protected UITableViewRowAnimation DeleteRowsAnimation { get; set; } = UITableViewRowAnimation.Automatic;
@@ -211,10 +212,13 @@ namespace Xamarin.Forms.Platform.iOS
 			{
 				if (Control == null)
 				{
-					_tableViewController = new FormsUITableViewController(e.NewElement);
+					if (Forms.IsiOS11OrNewer)
+					{
+						var parentNav = e.NewElement.FindParentOfType<NavigationPage>();
+						_usingLargeTitles = (parentNav != null && parentNav.OnThisPlatform().PrefersLargeTitles());
+					}
+					_tableViewController = new FormsUITableViewController(e.NewElement, _usingLargeTitles);
 					SetNativeControl(_tableViewController.TableView);
-					if (Forms.IsiOS9OrNewer)
-						Control.CellLayoutMarginsFollowReadableWidth = false;
 
 					_insetTracker = new KeyboardInsetTracker(_tableViewController.TableView, () => Control.Window, insets => Control.ContentInset = Control.ScrollIndicatorInsets = insets, point =>
 					{
@@ -983,10 +987,9 @@ namespace Xamarin.Forms.Platform.iOS
 					throw new NotSupportedException("Header cells do not support context actions");
 
 				var renderer = (CellRenderer)Internals.Registrar.Registered.GetHandlerForObject<IRegisterable>(cell);
-
 				view = new HeaderWrapperView { Cell = cell };
 				view.AddSubview(renderer.GetCell(cell, null, tableView));
-
+        
 				return view;
 			}
 
@@ -1100,7 +1103,14 @@ namespace Xamarin.Forms.Platform.iOS
 			public override void Scrolled(UIScrollView scrollView)
 			{
 				if (_isDragging && scrollView.ContentOffset.Y < 0)
+				{
 					_uiTableViewController.UpdateShowHideRefresh(true);
+				}
+
+				if (_isDragging && scrollView.ContentOffset.Y < -10f && _uiTableViewController._usingLargeTitles && Device.Info.CurrentOrientation.IsPortrait())
+				{
+					_uiTableViewController.ForceRefreshing();				
+				}					
 			}
 
 			public override string[] SectionIndexTitles(UITableView tableView)
@@ -1291,12 +1301,17 @@ namespace Xamarin.Forms.Platform.iOS
 
 		bool _refreshAdded;
 		bool _disposed;
+		internal bool _usingLargeTitles;
+		bool _isRefreshing;
 
-		public FormsUITableViewController(ListView element)
+		public FormsUITableViewController(ListView element, bool usingLargeTitles)
 		{
 			if (Forms.IsiOS9OrNewer)
 				TableView.CellLayoutMarginsFollowReadableWidth = false;
-			_refresh = new UIRefreshControl();
+
+			_usingLargeTitles = usingLargeTitles;
+
+			_refresh = new FormsRefreshControl(_usingLargeTitles);
 			_refresh.ValueChanged += OnRefreshingChanged;
 			_list = element;
 		}
@@ -1315,6 +1330,10 @@ namespace Xamarin.Forms.Platform.iOS
 				{
 					_refresh.BeginRefreshing();
 
+					//hack: On iOS11 with large titles we need to adjust the scroll offset manually 
+					//since our UITableView is not the first child of the UINavigationController
+					UpdateContentOffset(TableView.ContentOffset.Y - _refresh.Frame.Height);
+
 					//hack: when we don't have cells in our UITableView the spinner fails to appear
 					CheckContentSize();
 
@@ -1323,8 +1342,14 @@ namespace Xamarin.Forms.Platform.iOS
 			}
 			else
 			{
+				if (RefreshControl == null)
+					return;
+				
 				_refresh.EndRefreshing();
 
+				UpdateContentOffset(-1);
+
+				_isRefreshing = false;
 				if (!_list.IsPullToRefreshEnabled)
 					RemoveRefresh();
 			}
@@ -1351,6 +1376,19 @@ namespace Xamarin.Forms.Platform.iOS
 			//   5. We end up here; A refresh is in progress while being asked to disable pullToRefresh
 		}
 
+		//hack: Form some reason UIKit isn't allowing to scroll negative values with largetitles 
+		public void ForceRefreshing()
+		{
+			if (!_list.IsPullToRefreshEnabled)
+				return;
+			if (!_refresh.Refreshing && !_isRefreshing)
+			{
+				_isRefreshing = true;
+				UpdateContentOffset(TableView.ContentOffset.Y - _refresh.Frame.Height, _refresh.BeginRefreshing);
+				_list.SendRefreshing();
+			}
+		}
+
 		public void UpdateShowHideRefresh(bool shouldHide)
 		{
 			if (_list.IsPullToRefreshEnabled)
@@ -1407,6 +1445,8 @@ namespace Xamarin.Forms.Platform.iOS
 		{
 			if (_refresh.Refreshing)
 				_list.SendRefreshing();
+
+			_isRefreshing = _refresh.Refreshing;
 		}
 
 		void RemoveRefresh()
@@ -1414,11 +1454,55 @@ namespace Xamarin.Forms.Platform.iOS
 			if (!_refreshAdded)
 				return;
 
-			if (_refresh.Refreshing)
+			if (_refresh.Refreshing || _isRefreshing)
 				_refresh.EndRefreshing();
 
 			RefreshControl = null;
 			_refreshAdded = false;
+			_isRefreshing = false;
+		}
+
+		void UpdateContentOffset(nfloat offset, Action completed = null)
+		{
+			if (!_usingLargeTitles)
+				return;
+
+			UIView.Animate(0.2, () => TableView.ContentOffset = new CoreGraphics.CGPoint(TableView.ContentOffset.X, offset), completed);
+		}
+	}
+
+
+	public class FormsRefreshControl : UIRefreshControl
+	{
+		bool _usingLargeTitles;
+
+		public FormsRefreshControl(bool usingLargeTitles)
+		{
+			_usingLargeTitles = usingLargeTitles;
+		}
+
+		public override bool Hidden
+		{
+			get
+			{
+				return base.Hidden;
+			}
+			set
+			{
+				//hack: ahahah take that UIKit! 
+				//when using pull to refresh with Large tiles sometimes iOS tries to hide the UIRefreshControl
+				if (_usingLargeTitles && value && Refreshing)
+					return;
+				base.Hidden = value;
+			}
+		}
+
+		public override void BeginRefreshing()
+		{
+			base.BeginRefreshing();
+			if (!_usingLargeTitles)
+				return;
+			Hidden = false;
 		}
 	}
 }