feat: Replace Page with correct type when reloaded

Create an instance of the same type as the element being reloaded, and replace the old element in the visual tree rather than nesting inside of it.

src/Uno.UI.RemoteControl/HotReload/ClientHotReloadProcessor.Xaml.cs

@@ -11,6 +11,7 @@
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
 using Windows.UI.Xaml.Markup;
+using Windows.UI.Xaml.Media;
 
 namespace Uno.UI.RemoteControl.HotReload
 {
@@ -39,11 +40,11 @@ private async Task ReloadFile(FileReload fileReload)
                         {
 #if __IOS__
 						case UserControl userControl:
-							userControl.Content = XamlReader.Load(fileReload.Content) as UIKit.UIView;
+							userControl.Content = XamlReader.LoadUsingXClass(fileReload.Content) as UIKit.UIView;
 							break;
 #endif
                             case ContentControl content:
-                                content.Content = XamlReader.LoadUsingXClass(fileReload.Content);
+                                SwapViews(content, XamlReader.LoadUsingXClass(fileReload.Content) as ContentControl);
                                 break;
                         }
 					}
@@ -119,5 +120,32 @@ IEnumerable<IEnumerable<UIElement>> Dig()
 				}
 			}
 		}
+
+		private static void SwapViews(FrameworkElement oldView, FrameworkElement newView)
+		{
+			var parentAsContentControl = oldView.Parent as ContentControl;
+			parentAsContentControl = parentAsContentControl ?? (oldView.Parent as ContentPresenter)?.FindFirstParent<ContentControl>();
+
+			if (parentAsContentControl?.Content == oldView)
+			{
+				parentAsContentControl.Content = newView;
+			}
+			else
+			{
+				VisualTreeHelper.SwapViews(oldView, newView);
+			}
+
+			PropagateProperties(oldView, newView);
+		}
+
+		private static void PropagateProperties(FrameworkElement oldView, FrameworkElement newView)
+		{
+			newView.BaseUri = oldView.BaseUri;
+
+			if (oldView is Page oldPage && newView is Page newPage)
+			{
+				newPage.Frame = oldPage.Frame;
+			}
+		}
 	}
 }

src/Uno.UI/UI/Xaml/Media/VisualTreeHelper.Android.cs

@@ -0,0 +1,41 @@
+#nullable enable
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Android.Views;
+using Uno.Extensions;
+using Uno.UI;
+
+namespace Windows.UI.Xaml.Media
+{
+	public partial class VisualTreeHelper
+	{
+		internal static void SwapViews(UIElement oldView, UIElement newView)
+		{
+			var parentViewGroup = oldView?.Parent as ViewGroup;
+			var currentPosition = parentViewGroup?.GetChildren().IndexOf(oldView);
+
+			if (parentViewGroup != null && currentPosition != null && currentPosition.Value != -1)
+			{
+				parentViewGroup.RemoveViewAt(currentPosition.Value);
+
+				var unoViewGroup = parentViewGroup as UnoViewGroup;
+
+				if (unoViewGroup != null)
+				{
+					var newContentAsFrameworkElement = newView as IFrameworkElement;
+					if (newContentAsFrameworkElement != null)
+					{
+						newContentAsFrameworkElement.TemplatedParent = (unoViewGroup as IFrameworkElement)?.TemplatedParent;
+					}
+					unoViewGroup.AddView(newView, currentPosition.Value);
+				}
+				else
+				{
+					parentViewGroup.AddView(newView, currentPosition.Value);
+				}
+			}
+		}
+	}
+}

src/Uno.UI/UI/Xaml/Media/VisualTreeHelper.iOSmacOS.cs

@@ -0,0 +1,28 @@
+#nullable enable
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Uno.Extensions;
+
+namespace Windows.UI.Xaml.Media
+{
+	public partial class VisualTreeHelper
+	{
+		internal static void SwapViews(UIElement oldView, UIElement newView)
+		{
+			var currentPosition = oldView?.Superview?.Subviews.IndexOf(oldView) ?? -1;
+
+			if (currentPosition != -1) { 
+				var currentSuperview = oldView?.Superview;
+				oldView?.RemoveFromSuperview();
+
+#if __IOS__
+				currentSuperview?.InsertSubview(newView, currentPosition);
+#elif __MACOS__
+				currentSuperview.AddSubview(newView, NSWindowOrderingMode.Above, currentSuperview.Subviews[Math.Max(0, currentPosition-1)]);
+#endif
+		}
+	}
+	}
+}

src/Uno.UI/UI/Xaml/Media/VisualTreeHelper.netstd.cs

@@ -0,0 +1,27 @@
+#nullable enable
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Uno.Extensions;
+
+namespace Windows.UI.Xaml.Media
+{
+	public partial class VisualTreeHelper
+	{
+		internal static void SwapViews(UIElement oldView, UIElement newView)
+		{
+			if ((oldView as FrameworkElement)?.Parent is FrameworkElement parentElement)
+			{
+				var currentPosition = parentElement.GetChildren().IndexOf(oldView);
+
+				if (currentPosition != -1)
+				{
+					parentElement.RemoveChild(oldView);
+
+					parentElement.AddChild(newView, currentPosition);
+				}
+			}
+		}
+	}
+}