Use propagation method

Author: kubaflo

src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellFlyoutContentRenderer.cs

@@ -17,7 +17,6 @@ public class ShellFlyoutContentRenderer : UIViewController, IShellFlyoutContentR
 		UIContainerView _headerView;
 		UIContainerView _footerView;
 		View _footer;
-		View _header;
 		ShellTableViewController _tableViewController;
 		ShellFlyoutLayoutManager _shellFlyoutContentManager;
 		UIView[] _uIViews;
@@ -97,18 +96,8 @@ void UpdateFlyoutHeader()
 				_headerView.Dispose();
 			}
 
-			if (_header is not null)
-			{
-				_header.MeasureInvalidated += OnHeaderMeasureInvalidated;
-			}
-
-			_header = header;
-
 			if (header is not null)
-			{
 				_headerView = new ShellFlyoutHeaderContainer(((IShellController)_shellContext.Shell).FlyoutHeader);
-				_header.MeasureInvalidated += OnHeaderMeasureInvalidated;
-			}
 			else
 				_headerView = null;
 
@@ -133,7 +122,6 @@ void UpdateFlyoutFooter(View view)
 				var oldRenderer = (IPlatformViewHandler)_footer.Handler;
 				var oldFooterView = _footerView;
 				_tableViewController.FooterView = null;
-				_footer.MeasureInvalidated -= OnFooterMeasureInvalidated;
 				_footerView?.Disconnect();
 				_footerView = null;
 				_uIViews[FooterIndex] = null;
@@ -198,13 +186,6 @@ void AddViewInCorrectOrder(UIView newView, int previousIndex)
 			View.AddSubview(newView);
 		}
 
-		void OnHeaderMeasureInvalidated(object sender, System.EventArgs e)
-		{
-			var size = _headerView?.SizeThatFits(new CGSize(View.Frame.Width, double.PositiveInfinity));
-			if (size is not null)
-				_headerView.Frame = new CoreGraphics.CGRect(_headerView.Frame.X, _headerView.Frame.Y, size.Value.Width, size.Value.Height);
-		}
-
 		void OnFooterMeasureInvalidated(object sender, System.EventArgs e)
 		{
 			ReMeasureFooter();

src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellFlyoutHeaderContainer.cs

@@ -1,9 +1,10 @@
 #nullable disable
+using CoreGraphics;
 using UIKit;
 
 namespace Microsoft.Maui.Controls.Platform.Compatibility
 {
-	internal class ShellFlyoutHeaderContainer : UIContainerView
+	internal class ShellFlyoutHeaderContainer : UIContainerView, IPlatformMeasureInvalidationController
 	{
 		Thickness _safearea = Thickness.Zero;
 
@@ -34,6 +35,14 @@ public override Thickness Margin
 			}
 		}
 
+		void IPlatformMeasureInvalidationController.InvalidateAncestorsMeasuresWhenMovedToWindow() { }
+
+		void IPlatformMeasureInvalidationController.InvalidateMeasure(bool isPropagating)
+		{
+			var size = SizeThatFits(new CGSize(Superview.Frame.Width, double.PositiveInfinity));
+			Frame = new CGRect(Frame.X, Frame.Y, size.Width, size.Height);
+		}
+
 		public override void LayoutSubviews()
 		{
 			if (!UpdateSafeAreaMargin())