[Android] Eagerly dispose children of ListViews to prevent ObjectDisposed exception (#1063)

* Add repro for 57910

* [Android] Dispose cells explicitly

* [Android] Add default constructors to prevent crash on dispose

* [Android] Don't try to dispose headers and footers

1 files changed, 53 insertions, 2 deletions

diff --git a/Xamarin.Forms.ControlGallery.Android/CustomRenderers.cs b/Xamarin.Forms.ControlGallery.Android/CustomRenderers.cs
index 33310332..e219b82c 100644
--- a/Xamarin.Forms.ControlGallery.Android/CustomRenderers.cs
+++ b/Xamarin.Forms.ControlGallery.Android/CustomRenderers.cs
@@ -31,6 +31,8 @@ using Xamarin.Forms.Controls.Issues;
 [assembly: ExportRenderer(typeof(Bugzilla42000._42000NumericEntryNoDecimal), typeof(EntryRendererNoDecimal))]
 [assembly: ExportRenderer(typeof(Bugzilla42000._42000NumericEntryNoNegative), typeof(EntryRendererNoNegative))]
 //[assembly: ExportRenderer(typeof(AndroidHelpText.HintLabel), typeof(HintLabel))]
+[assembly: ExportRenderer(typeof(Bugzilla57910QuickCollectNavigationPage), typeof(QuickCollectNavigationPage))]
+
 
 [assembly: ExportRenderer(typeof(Xamarin.Forms.Controls.Issues.NoFlashTestNavigationPage), typeof(Xamarin.Forms.ControlGallery.Android.NoFlashTestNavigationPage))]
 
@@ -523,7 +525,6 @@ namespace Xamarin.Forms.ControlGallery.Android
 		}
 	}
 
-
 	//public class HintLabel : Xamarin.Forms.Platform.Android.AppCompat.LabelRenderer
 	//{
 	//	public HintLabel()
@@ -531,7 +532,7 @@ namespace Xamarin.Forms.ControlGallery.Android
 	//		Hint = AndroidHelpText.HintLabel.Success;
 	//	}
  // }
-
+ 
 	public class NoFlashTestNavigationPage : Xamarin.Forms.Platform.Android.AppCompat.NavigationPageRenderer
 	{
 		protected override void SetupPageTransition(global::Android.Support.V4.App.FragmentTransaction transaction, bool isPush)
@@ -539,5 +540,55 @@ namespace Xamarin.Forms.ControlGallery.Android
 			transaction.SetTransition((int)FragmentTransit.None);
 		}
 	}
+
+	public class QuickCollectNavigationPage : Xamarin.Forms.Platform.Android.AppCompat.NavigationPageRenderer
+	{
+		bool _disposed;
+		NavigationPage _page;
+
+		protected override void OnElementChanged(ElementChangedEventArgs<NavigationPage> e)
+		{
+			base.OnElementChanged(e);
+
+			if (e.NewElement == null)
+			{
+				if (e.OldElement != null)
+				{
+					((IPageController)e.OldElement).InternalChildren.CollectionChanged -= OnInternalPageCollectionChanged;
+				}
+
+				return;
+			}
+
+			((IPageController)e.NewElement).InternalChildren.CollectionChanged += OnInternalPageCollectionChanged;
+		}
+
+		private void OnInternalPageCollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
+		{
+			if (e.OldItems != null)
+			{
+				// Force a collection on popped to simulate the problem.
+				GC.Collect();
+			}
+		}
+
+		protected override void Dispose(bool disposing)
+		{
+			if (_disposed)
+			{
+				return;
+			}
+
+			_disposed = true;
+
+			if (disposing && _page != null)
+			{
+				_page.InternalChildren.CollectionChanged -= OnInternalPageCollectionChanged;
+				_page = null;
+			}
+
+			base.Dispose(disposing);
+		}
+	}
 }