fix(iOS): CommandBar updates on navigation unoplatform#3017

src/Uno.UI/Controls/CommandBarHelper.iOS.cs

@@ -1,4 +1,4 @@
-#if __IOS__
+#if __IOS__
 #nullable enable
 using System;
 using System.Linq;
@@ -101,6 +101,16 @@ public static void PageDidDisappear(UIViewController pageController)
 			}
 		}
 
+		public static void PageWillDisappear(UIViewController pageController)
+		{
+			var topCommandBar = pageController.FindTopCommandBar();
+			if (topCommandBar != null)
+			{
+				// Set the native navigation bar to null so it does not render when the page is not visible
+				SetNavigationBar(topCommandBar, null);
+			}
+		}
+
 		private static CommandBar? FindTopCommandBar(this UIViewController controller)
 		{
 			return (controller.View as Page)?.TopAppBar as CommandBar

src/Uno.UI/Controls/NativeFramePresenter.iOS.cs

@@ -704,6 +704,19 @@ public override void ViewWillAppear(bool animated)
 				}
 			}
 
+			public override void ViewWillDisappear(bool animated)
+			{
+				try
+				{
+					base.ViewWillDisappear(animated);
+					CommandBarHelper.PageWillDisappear(this);
+				}
+				catch (Exception e)
+				{
+					Application.Current.RaiseRecoverableUnhandledException(e);
+				}
+			}
+
 			public override void ViewDidDisappear(bool animated)
 			{
 				try