[iOS/Critical] Fix ListView memory leaks (#524)

* fix memory leaks

added sample code

changed page name

Changed page title

add screen instructions

fix copy paste error

change subview dispose logic

Fix context action memory leak

add sample code

change custom page names

Revert "change custom page names"

This reverts commit 7aaab2625d9526080ca5c51c02e909f09ee3f610.

changed class names

changes

UI test for 32206

update ui test

fix whitespace

UITests done

* run UI tests on iOS only

* fix code style

* dispose prototype

* fix child renderer issue

* add null check

2 files changed, 28 insertions, 6 deletions

diff --git a/Xamarin.Forms.Platform.iOS/Cells/CellTableViewCell.cs b/Xamarin.Forms.Platform.iOS/Cells/CellTableViewCell.cs
index e32e86cd..b42f69f4 100644
--- a/Xamarin.Forms.Platform.iOS/Cells/CellTableViewCell.cs
+++ b/Xamarin.Forms.Platform.iOS/Cells/CellTableViewCell.cs
@@ -7,8 +7,8 @@ namespace Xamarin.Forms.Platform.iOS
 	public class CellTableViewCell : UITableViewCell, INativeElementView
 	{
 		Cell _cell;
-
 		public Action<object, PropertyChangedEventArgs> PropertyChanged;
+		bool _disposed;
 
 		public CellTableViewCell(UITableViewCellStyle style, string key) : base(style, key)
 		{
@@ -95,5 +95,21 @@ namespace Xamarin.Forms.Platform.iOS
 
 			return nativeCell;
 		}
+
+		protected override void Dispose(bool disposing)
+		{
+			if (_disposed)
+				return;
+
+			if (disposing)
+			{
+				PropertyChanged = null;
+				_cell = null;
+			}
+
+			_disposed = true;
+
+			base.Dispose(disposing);
+		}
 	}
 }
\ No newline at end of file
diff --git a/Xamarin.Forms.Platform.iOS/Cells/ViewCellRenderer.cs b/Xamarin.Forms.Platform.iOS/Cells/ViewCellRenderer.cs
index 8f8a92ce..30c17234 100644
--- a/Xamarin.Forms.Platform.iOS/Cells/ViewCellRenderer.cs
+++ b/Xamarin.Forms.Platform.iOS/Cells/ViewCellRenderer.cs
@@ -48,9 +48,12 @@ namespace Xamarin.Forms.Platform.iOS
 		internal class ViewTableCell : UITableViewCell, INativeElementView
 		{
 			WeakReference<IVisualElementRenderer> _rendererRef;
-
 			ViewCell _viewCell;
 
+			Element INativeElementView.Element => ViewCell;
+			internal bool SupressSeparator { get; set; }
+			bool _disposed;
+
 			public ViewTableCell(string key) : base(UITableViewCellStyle.Default, key)
 			{
 			}
@@ -66,10 +69,6 @@ namespace Xamarin.Forms.Platform.iOS
 				}
 			}
 
-			Element INativeElementView.Element => ViewCell;
-
-			internal bool SupressSeparator { get; set; }
-
 			public override void LayoutSubviews()
 			{
 				//This sets the content views frame.
@@ -115,6 +114,9 @@ namespace Xamarin.Forms.Platform.iOS
 
 			protected override void Dispose(bool disposing)
 			{
+				if (_disposed)
+					return;
+
 				if (disposing)
 				{
 					IVisualElementRenderer renderer;
@@ -126,8 +128,12 @@ namespace Xamarin.Forms.Platform.iOS
 
 						_rendererRef = null;
 					}
+
+					_viewCell = null;
 				}
 
+				_disposed = true;
+
 				base.Dispose(disposing);
 			}