Add new xplat event to to propagate FlyoutItemsChanged events to the …

…platforms (#13195) fixes #11214

* Add new xplat event to update FlyoutItems from

* - always send flyout item changes

* - fix flyout changed propagation

* - add additional scenario for Sending Flyout Items Changed Event

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue11214.cs

@@ -0,0 +1,104 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Text;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UITests;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 11214, "When adding FlyoutItems during Navigating only first one is shown",
+		PlatformAffected.iOS)]
+#if UITEST
+	[NUnit.Framework.Category(Core.UITests.UITestCategories.Github10000)]
+	[NUnit.Framework.Category(UITestCategories.Shell)]
+#endif
+	public class Issue11214 : TestShell
+	{
+		FlyoutItem _itemexpanderItems;
+		protected override void Init()
+		{
+			_itemexpanderItems = new FlyoutItem()
+			{
+				Title = "Expando Magic",
+				FlyoutDisplayOptions = FlyoutDisplayOptions.AsMultipleItems
+			};
+
+			ContentPage contentPage = new ContentPage()
+			{
+				Content = new StackLayout()
+				{
+					Children =
+					{
+						new Label()
+						{
+							Text = "Open the Flyout",
+							AutomationId = "PageLoaded"
+						}
+					}
+				}
+			};
+
+			AddFlyoutItem(contentPage, "Top Item");
+
+			var flyoutItem = AddFlyoutItem("Click Me and You Should see 2 Items show up");
+			flyoutItem.Route = "ExpandMe";
+			flyoutItem.AutomationId = "ExpandMe";
+			Items.Add(_itemexpanderItems);
+		}
+
+		protected override void OnNavigating(ShellNavigatingEventArgs args)
+		{
+			base.OnNavigating(args);
+
+			if(!args.Target.FullLocation.ToString().Contains("ExpandMe"))
+			{
+				return;
+			}
+
+			args.Cancel();
+
+			if (_itemexpanderItems.Items.Count == 0 ||
+				_itemexpanderItems.Items[0].Items.Count == 0)
+			{
+				for (int i = 0; i < 2; i++)
+				{
+					_itemexpanderItems.Items.Add(new ShellContent()
+					{
+						Title = $"Some Item: {i}",
+						Content = new ContentPage()
+					});
+				}
+			}
+			else
+			{
+				_itemexpanderItems.Items.Clear();
+			}
+		}
+
+#if UITEST
+		[Test]
+		public void FlyoutItemChangesPropagateCorrectlyToPlatformForShellElementsNotCurrentlyActive()
+		{
+			RunningApp.WaitForElement("PageLoaded");
+			TapInFlyout("ExpandMe", makeSureFlyoutStaysOpen: true);
+
+			for (int i = 0; i < 2; i++)
+				RunningApp.WaitForElement($"Some Item: {i}");
+
+			TapInFlyout("ExpandMe", makeSureFlyoutStaysOpen: true);
+
+			for (int i = 0; i < 2; i++)
+				RunningApp.WaitForNoElement($"Some Item: {i}");
+		}
+#endif
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -10,6 +10,7 @@
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="$(MSBuildThisFileDirectory)CollectionViewGroupTypeIssue.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue11214.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue13109.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue4720.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue10897.xaml.cs">
@@ -2607,4 +2608,4 @@
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
   </ItemGroup>
-</Project>
+</Project>

Xamarin.Forms.Core/Shell/IShellController.cs

@@ -19,6 +19,7 @@ public interface IFlyoutBehaviorObserver
 	public interface IShellController : IPageController
 	{
 		event EventHandler StructureChanged;
+		event EventHandler FlyoutItemsChanged;
 
 		View FlyoutHeader { get; }
 

Xamarin.Forms.Core/Shell/Shell.cs

@@ -65,7 +65,7 @@ static void OnFlyoutItemIsVisibleChanged(BindableObject bindable, object oldValu
 			if (bindable is Element element)
 				element
 					.FindParentOfType<Shell>()
-					?.SendStructureChanged();
+					?.SendFlyoutItemsChanged();
 		}
 
 		public static readonly BindableProperty TabBarIsVisibleProperty =
@@ -294,6 +294,14 @@ event EventHandler IShellController.StructureChanged
 
 		event EventHandler _structureChanged;
 
+		event EventHandler IShellController.FlyoutItemsChanged
+		{
+			add { _flyoutItemsChanged += value; }
+			remove { _flyoutItemsChanged -= value; }
+		}
+
+		event EventHandler _flyoutItemsChanged;
+
 		View IShellController.FlyoutHeader => FlyoutHeaderView;
 		View IShellController.FlyoutFooter => FlyoutFooterView;
 
@@ -570,6 +578,7 @@ void Initialize()
 			{
 				SetCurrentItem();
 				SendStructureChanged();
+				SendFlyoutItemsChanged();
 			};
 
 			async void SetCurrentItem()
@@ -814,8 +823,23 @@ protected override void OnBindingContextChanged()
 			if (FlyoutFooterView != null)
 				SetInheritedBindingContext(FlyoutFooterView, BindingContext);
 		}
+
+
+		internal void SendFlyoutItemsChanged()
+		{
+			if (UpdateFlyoutGroupings())
+				_flyoutItemsChanged?.Invoke(this, EventArgs.Empty);
+		}
 
 		List<List<Element>> IShellController.GenerateFlyoutGrouping()
+		{
+			if(_currentFlyoutViews == null)
+				UpdateFlyoutGroupings();
+
+			return _currentFlyoutViews;
+		}
+
+		bool UpdateFlyoutGroupings()
 		{
 			// The idea here is to create grouping such that the Flyout would
 			// render correctly if it renderered each item in the groups in order
@@ -926,11 +950,11 @@ List<List<Element>> IShellController.GenerateFlyoutGrouping()
 				}
 
 				if (!hasChanged)
-					return _currentFlyoutViews;
+					return false;
 			}
 
 			_currentFlyoutViews = result;
-			return result;
+			return true;
 
 			bool ShowInFlyoutMenu(BindableObject bo)
 			{

Xamarin.Forms.Core/Shell/ShellGroupItem.cs

@@ -1,9 +1,16 @@
-namespace Xamarin.Forms
+using System;
+
+namespace Xamarin.Forms
 {
 	public class ShellGroupItem : BaseShellItem
 	{
 		public static readonly BindableProperty FlyoutDisplayOptionsProperty =
-			BindableProperty.Create(nameof(FlyoutDisplayOptions), typeof(FlyoutDisplayOptions), typeof(ShellItem), FlyoutDisplayOptions.AsSingleItem, BindingMode.OneTime);
+			BindableProperty.Create(nameof(FlyoutDisplayOptions), typeof(FlyoutDisplayOptions), typeof(ShellGroupItem), FlyoutDisplayOptions.AsSingleItem, BindingMode.OneTime, propertyChanged: OnFlyoutDisplayOptionsPropertyChanged);
+
+		static void OnFlyoutDisplayOptionsPropertyChanged(BindableObject bindable, object oldValue, object newValue)
+		{
+			((Element)bindable).FindParentOfType<Shell>()?.SendFlyoutItemsChanged();
+		}
 
 		public FlyoutDisplayOptions FlyoutDisplayOptions
 		{

Xamarin.Forms.Core/Shell/ShellItem.cs

@@ -164,9 +164,12 @@ public ShellSection CurrentItem
 
 		internal void SendStructureChanged()
 		{
-			if (Parent is Shell shell && IsVisibleItem)
+			if (Parent is Shell shell)
 			{
-				shell.SendStructureChanged();
+				if (IsVisibleItem)
+					shell.SendStructureChanged();
+
+				shell.SendFlyoutItemsChanged();
 			}
 		}
 

Xamarin.Forms.Core/Shell/ShellSection.cs

@@ -622,9 +622,12 @@ bool IsNavigationAnimated(BindableObject bo)
 
 		internal void SendStructureChanged()
 		{
-			if (Parent?.Parent is Shell shell && IsVisibleSection)
+			if (Parent?.Parent is Shell shell)
 			{
-				shell.SendStructureChanged();
+				if (IsVisibleSection)
+					shell.SendStructureChanged();
+
+				shell.SendFlyoutItemsChanged();
 			}
 		}
 

Xamarin.Forms.Platform.Android/Renderers/ShellFlyoutRecyclerAdapter.cs

@@ -25,7 +25,7 @@ public ShellFlyoutRecyclerAdapter(IShellContext shellContext, Action<Element> se
 		{
 			_shellContext = shellContext;
 
-			ShellController.StructureChanged += OnShellStructureChanged;
+			ShellController.FlyoutItemsChanged += OnFlyoutItemsChanged;
 
 			_listItems = GenerateItemList();
 			_selectedCallback = selectedCallback;
@@ -197,7 +197,7 @@ protected virtual List<AdapterListItem> GenerateItemList()
 			return result;
 		}
 
-		protected virtual void OnShellStructureChanged(object sender, EventArgs e)
+		protected virtual void OnFlyoutItemsChanged(object sender, EventArgs e)
 		{
 			var newListItems = GenerateItemList();
 
@@ -217,7 +217,7 @@ protected override void Dispose(bool disposing)
 
 			if (disposing)
 			{
-				((IShellController)Shell).StructureChanged -= OnShellStructureChanged;
+				((IShellController)Shell).FlyoutItemsChanged -= OnFlyoutItemsChanged;
 
 				_elementViewHolder?.Dispose();
 

Xamarin.Forms.Platform.UAP/Shell/ShellRenderer.cs

@@ -1,6 +1,8 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.ComponentModel;
+using System.Linq;
 using Windows.Foundation.Metadata;
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
@@ -32,6 +34,7 @@ public class ShellRenderer : Microsoft.UI.Xaml.Controls.NavigationView, IVisualE
 		List<List<Element>> _flyoutGrouping;
 		ShellItemRenderer ItemRenderer { get; }
 		IShellController ShellController => (IShellController)_shell;
+		ObservableCollection<object> FlyoutItems = new ObservableCollection<object>();
 
 		public ShellRenderer()
 		{
@@ -43,6 +46,7 @@ public ShellRenderer()
 			Content = ItemRenderer = CreateShellItemRenderer();
 			MenuItemTemplateSelector = CreateShellFlyoutTemplateSelector();
 			Style = (Windows.UI.Xaml.Style)Windows.UI.Xaml.Application.Current.Resources["ShellNavigationView"];
+			MenuItemsSource = FlyoutItems;
 		}
 
 		async void OnBackRequested(Microsoft.UI.Xaml.Controls.NavigationView sender, Microsoft.UI.Xaml.Controls.NavigationViewBackRequestedEventArgs args)
@@ -317,7 +321,7 @@ protected virtual void OnElementSet(Shell shell)
 			ShellController.AddFlyoutBehaviorObserver(this);
 			ShellController.AddAppearanceObserver(this, shell);
 			ShellController.ItemsCollectionChanged += OnItemsCollectionChanged;
-			ShellController.StructureChanged += OnStructureChanged;
+			ShellController.FlyoutItemsChanged += OnFlyoutItemsChanged;
 			UpdateFlyoutBackgroundColor();
 
 			_shell.Navigated += OnShellNavigated;
@@ -370,7 +374,7 @@ void UpdateToolBar()
 			}
 		}
 
-		void OnStructureChanged(object sender, EventArgs e)
+		void OnFlyoutItemsChanged(object sender, EventArgs e)
 		{
 			UpdateMenuItemSource();
 		}
@@ -386,17 +390,31 @@ void UpdateMenuItemSource()
 			if (_flyoutGrouping != newGrouping)
 			{
 				_flyoutGrouping = newGrouping;
-				MenuItemsSource = IterateItems(newGrouping);
+				var newItems = IterateItems(newGrouping).ToList();
+
+				foreach (var item in newItems)
+				{
+					if (!FlyoutItems.Contains(item))
+						FlyoutItems.Add(item);
+				}
+
+				for (var i = FlyoutItems.Count - 1; i >= 0; i--)
+				{
+					var item = FlyoutItems[i];
+					if (!newItems.Contains(item))
+						FlyoutItems.RemoveAt(i);
+				}
 			}
 		}
 
 		IEnumerable<object> IterateItems(List<List<Element>> groups)
 		{
+			int separatorNumber = 0;
 			foreach (var group in groups)
 			{
 				if (group.Count > 0 && group != groups[0])
 				{
-					yield return new MenuFlyoutSeparator(); // Creates a separator
+					yield return new FlyoutItemMenuSeparator(separatorNumber++); // Creates a separator
 				}
 				foreach (var item in group)
 				{
@@ -405,6 +423,19 @@ IEnumerable<object> IterateItems(List<List<Element>> groups)
 			}
 		}
 
+		class FlyoutItemMenuSeparator : MenuFlyoutSeparator
+		{
+			public FlyoutItemMenuSeparator(int separatorNumber)
+			{
+				Id = separatorNumber;
+			}
+
+			public int Id { get; set; }
+			public override int GetHashCode() => Id.GetHashCode();
+			public override bool Equals(object obj) =>
+				obj is FlyoutItemMenuSeparator fim && fim.Id == Id;
+		}
+
 		void SwitchShellItem(ShellItem newItem, bool animate = true)
 		{
 			SelectedItem = newItem;

Xamarin.Forms.Platform.iOS/Renderers/ShellTableViewController.cs

@@ -33,7 +33,7 @@ public ShellTableViewController(IShellContext context, Action<Element> onElement
 			_source = CreateShellTableViewSource();
 			_source.ScrolledEvent += OnScrolled;
 
-			ShellController.StructureChanged += OnStructureChanged;
+			ShellController.FlyoutItemsChanged += OnFlyoutItemsChanged;
 			_context.Shell.PropertyChanged += OnShellPropertyChanged;
 		}
 
@@ -90,7 +90,7 @@ void OnHeaderFooterSizeChanged(object sender, EventArgs e)
 			LayoutParallax();
 		}
 
-		void OnStructureChanged(object sender, EventArgs e)
+		void OnFlyoutItemsChanged(object sender, EventArgs e)
 		{
 			_source.ClearCache();
 			TableView.ReloadData();
@@ -181,8 +181,8 @@ protected override void Dispose(bool disposing)
 
 			if (disposing)
 			{
-				if ((_context?.Shell as IShellController) != null)
-					((IShellController)_context.Shell).StructureChanged -= OnStructureChanged;
+				if (ShellController != null)
+					ShellController.FlyoutItemsChanged -= OnFlyoutItemsChanged;
 
 				if (_source != null)
 					_source.ScrolledEvent -= OnScrolled;