Call RootViewChanged when setting ContentView to null (#20052)

* Call RootViewChanged when setting ContentView to null

* When switching RootView, Reinitialize VisualDiagnosticsLayer

---------

Co-authored-by: Shane Neuville <shneuvil@microsoft.com>

src/Controls/src/Core/Compatibility/Handlers/Shell/Android/ShellRenderer.cs

@@ -214,9 +214,6 @@ protected virtual void OnElementSet(Shell shell)
 			((IShellController)shell).AddAppearanceObserver(this, shell);
 
 			SwitchFragment(FragmentManager, _frameLayout, shell.CurrentItem, false);
-
-			var rootManager = _mauiContext.GetNavigationRootManager();
-			rootManager?.OnWindowContentPlatformViewCreated();
 		}
 
 		IShellItemRenderer _currentView;

src/Core/src/Handlers/Window/WindowHandler.Android.cs

@@ -73,7 +73,12 @@ private protected override void OnDisconnectHandler(object platformView)
 		void OnRootViewChanged(object? sender, EventArgs e)
 		{
 			if (VirtualView.VisualDiagnosticsOverlay != null && _rootManager?.RootView is ViewGroup)
+			{
+				if (VirtualView.VisualDiagnosticsOverlay.IsPlatformViewInitialized)
+					VirtualView.VisualDiagnosticsOverlay.Deinitialize();
+
 				VirtualView.VisualDiagnosticsOverlay.Initialize();
+			}
 		}
 
 		// This is here to try and ensure symmetry with disconnect code between test handler

src/Core/src/Platform/Android/Navigation/NavigationRootManager.cs

@@ -95,7 +95,7 @@ internal void Connect(IView view, IMauiContext? mauiContext = null)
 		// this is called after the Window.Content is created by
 		// the fragment. We can't just create views on demand
 		// need to let the fragments fall
-		internal void OnWindowContentPlatformViewCreated()
+		void OnWindowContentPlatformViewCreated()
 		{
 			RootViewChanged?.Invoke(this, EventArgs.Empty);
 
@@ -155,6 +155,8 @@ void SetContentView(IView? view)
 
 				if (FragmentManager.IsDestroyed(context))
 					_viewFragment = null;
+
+				RootViewChanged?.Invoke(this, EventArgs.Empty);
 			}
 			else
 			{