Wait for parent to get set before realizing titleview

src/Controls/samples/Controls.Sample.UITests/Issues/Issue17347.cs

@@ -0,0 +1,65 @@
+using System;
+using Microsoft.Maui.Controls;
+
+namespace Maui.Controls.Sample.Issues
+{
+	[Issue(IssueTracker.Github, 17347, "Setting a new TitleView on an already created page crashes iOS", PlatformAffected.iOS)]
+	public class Issue17347 : TestContentPage
+	{
+		protected override void Init()
+		{
+			var navPage = new NavigationPage(new MainPage());
+			NavigatedTo += Issue16499_NavigatedTo;
+
+			async void Issue16499_NavigatedTo(object sender, NavigatedToEventArgs e)
+			{
+				NavigatedTo -= Issue16499_NavigatedTo;
+
+				await Navigation.PushModalAsync(navPage);
+				await navPage.Navigation.PushAsync(new MainPage());
+				await navPage.Navigation.PushAsync(new MainPage());
+				await navPage.Navigation.PopAsync();
+				await navPage.Navigation.PopAsync();
+			}
+		}
+
+		public partial class MainPage : ContentPage
+		{
+			Label TopView;
+			static int i = 0;
+			protected override void OnAppearing()
+			{
+				Content = new VerticalStackLayout()
+				{
+					new Button()
+					{
+						AutomationId = "PopMeButton",
+						Command = new Command(async () =>
+						{
+							if (Navigation.NavigationStack.Count == 1)
+								await Navigation.PopModalAsync();
+							else
+								await Navigation.PopAsync();
+						}),
+						Text = "Click to Pop This Page If Needed"
+					}
+				};
+
+				var increment = $"{i++}";
+				TopView = new()
+				{
+					AutomationId = "TitleViewLabel" + increment
+				};
+
+				TopView.SetBinding(Label.TextProperty, "AutomationId");
+				TopView.BindingContext = TopView;
+
+				TopView.WidthRequest = App.Current.Windows[0].Page.Width / 2;
+				NavigationPage.SetTitleView(this, TopView);
+				NavigationPage.SetHasNavigationBar(this, true);
+				NavigationPage.SetHasBackButton(this, false);
+				base.OnAppearing();
+			}
+		}
+	}
+}

src/Controls/src/Core/Compatibility/Handlers/NavigationPage/iOS/NavigationRenderer.cs

@@ -1759,14 +1759,40 @@ public Container(View view, UINavigationBar bar) : base(bar.Bounds)
 				if (view != null)
 				{
 					_view = view;
-					var platformView = view.ToPlatform(view.FindMauiContext());
-					_child = (IPlatformViewHandler)view.Handler;
-					AddSubview(platformView);
+
+					if (_view.Parent is null)
+					{
+						_view.ParentSet += OnTitleViewParentSet;
+					}
+					else
+					{
+						SetupTitleView();
+					}
 				}
 
 				ClipsToBounds = true;
 			}
 
+			void OnTitleViewParentSet(object sender, EventArgs e)
+			{
+				if (sender is View view)
+					view.ParentSet -= OnTitleViewParentSet;
+
+				SetupTitleView();
+			}
+
+			void SetupTitleView()
+			{
+				var mauiContext = _view.FindMauiContext();
+				if (_view is not null && mauiContext is not null)
+				{
+					var platformView = _view.ToPlatform(mauiContext);
+					_child = (IPlatformViewHandler)_view.Handler;
+					AddSubview(platformView);
+				}
+
+			}
+
 			public override CGSize IntrinsicContentSize => UILayoutFittingExpandedSize;
 
 			nfloat IconHeight => _icon?.Frame.Height ?? 0;
@@ -1874,6 +1900,11 @@ protected override void Dispose(bool disposing)
 						_child = null;
 					}
 
+					if (_view is not null)
+					{
+						_view.ParentSet -= OnTitleViewParentSet;
+					}
+
 					_view = null;
 
 					_icon?.Dispose();

src/Controls/tests/UITests/Tests/Issues/Issue17347.cs

@@ -0,0 +1,29 @@
+using System.Drawing;
+using Microsoft.Maui.Appium;
+using NUnit.Framework;
+using OpenQA.Selenium.Appium.MultiTouch;
+using TestUtils.Appium.UITests;
+
+namespace Microsoft.Maui.AppiumTests.Issues
+{
+	public class Issue17347 : _IssuesUITest
+	{
+		public Issue17347(TestDevice device) : base(device)
+		{
+		}
+
+		public override string Issue => "Setting a new TitleView on an already created page crashes iOS";
+
+		[Test]
+		public void AppDoesntCrashWhenSettingNewTitleViewOnExistingPage() {
+			try
+			{
+				App.WaitForElement("TitleViewLabel4", timeout: TimeSpan.FromSeconds(4));
+			}
+			finally
+			{
+				App.Tap("PopMeButton");
+			}
+		}
+	}
+}