feat: Implemented SelectedItemsVector and SelectedTreeNodeVector

src/Uno.UI/Microsoft/UI/Xaml/Controls/TreeView/SelectedItemsVector.cs

@@ -0,0 +1,92 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Windows.Foundation.Collections;
+
+namespace Microsoft.UI.Xaml.Controls
+{
+	//// Similiar to SelectedNodesVector above, we need to make decisions before the item is inserted or removed.
+	//// we can't use vector change events because the event already happened when event hander gets called.
+	internal class SelectedItemsVector : ObservableVector<object>
+	{
+		private TreeViewViewModel m_viewModel;
+
+		public void SetViewModel(TreeViewViewModel viewModel)
+		{
+			m_viewModel = viewModel;
+		}
+
+		internal void Append(object item) => InsertAt(Count, item);
+
+		internal void InsertAt(int index, object item)
+		{
+			if (!Contains(item))
+			{
+				GetVectorInnerImpl().Insert(index, item);
+
+				// Keep SelectedNodes and SelectedItems in sync
+				var viewModel = m_viewModel;
+				if (viewModel != null)
+				{
+					var selectedNodes = viewModel.SelectedNodes;
+					if (selectedNodes.Count != Count)
+					{
+						var listControl = viewModel.ListControl;
+						if (listControl != null)
+						{
+							var node = listControl.NodeFromItem(item);
+							if (node != null)
+							{
+								selectedNodes.Insert(index, node);
+							}
+						}
+					}
+				}
+			}
+		}
+
+		internal void SetAt(int index, object item)
+		{
+			RemoveAt(index);
+			InsertAt(index, item);
+		}
+
+		public override void RemoveAt(int index)
+		{
+			GetVectorInnerImpl().RemoveAt(index);
+
+			// Keep SelectedNodes and SelectedItems in sync
+			var viewModel = m_viewModel;
+			if (viewModel != null)
+			{
+				var selectedNodes = viewModel.SelectedNodes;
+				if (Count != selectedNodes.Count)
+				{
+					selectedNodes.RemoveAt(index);
+				}
+			}
+		}
+
+		internal void RemoveAtEnd() => RemoveAt(Count - 1);
+
+		internal void ReplaceAll(IEnumerable<object> items)
+		{
+			Clear();
+
+			foreach (var node in items)
+			{
+				Append(node);
+			}
+		}
+
+		public override void Clear()
+		{
+			while (Count > 0)
+			{
+				RemoveAtEnd();
+			}
+		}
+	}
+}

src/Uno.UI/Microsoft/UI/Xaml/Controls/TreeView/SelectedTreeNodeVector.cs

@@ -0,0 +1,127 @@
+using System.Collections.Generic;
+using Microsoft.UI.Xaml.Controls;
+using Windows.Foundation.Collections;
+
+namespace Microsoft.UI.Xaml.Controls
+{
+	// Need to update node selection states on UI before vector changes.
+	// Listen on vector change events don't solve the problem because the event already happened when the event handler gets called.
+	// i.e. the node is alreay gone when we get to ItemRemoved callback.
+	internal class SelectedTreeNodeVector : ObservableVector<TreeViewNode>
+	{
+		TreeViewViewModel m_viewModel = null;
+
+		private void UpdateSelection(TreeViewNode node, TreeNodeSelectionState state)
+		{
+			if (node.SelectionState != state)
+			{
+				var viewModel = m_viewModel;
+
+				if (viewModel != null)
+				{
+					viewModel.UpdateSelection(node, state);
+					viewModel.NotifyContainerOfSelectionChange(node, state);
+				}
+			}
+		}
+
+		public void SetViewModel(TreeViewViewModel viewModel)
+		{
+			m_viewModel = viewModel;
+		}
+
+		internal void Append(TreeViewNode node) => InsertAt(Count, node);
+
+		public override void Add(TreeViewNode node) => Append(node);
+
+		internal void InsertAt(int index, TreeViewNode node)
+		{
+			if (!Contains(node))
+			{
+				// UpdateSelection will call InsertAtCore
+				UpdateSelection(node, TreeNodeSelectionState.Selected);
+			}
+		}
+
+		public override void Insert(int index, TreeViewNode node) => InsertAt(index, node);
+
+		internal void SetAt(int index, TreeViewNode node)
+		{
+			RemoveAt(index);
+			InsertAt(index, node);
+		}
+
+		public override TreeViewNode this[int index]
+		{
+			get => base[index];
+			set => SetAt(index, value);
+		}
+
+		public override void RemoveAt(int index)
+		{
+			var inner = GetVectorInnerImpl();
+			var oldNode = inner[index];
+			// UpdateNodeSelection will call RemoveAtCore
+			UpdateSelection(oldNode, TreeNodeSelectionState.UnSelected);
+		}
+
+		internal void RemoveAtEnd() => RemoveAt(Count - 1);
+
+		internal void ReplaceAll(IEnumerable<TreeViewNode> nodes)
+		{
+			Clear();
+
+			foreach (var node in nodes)
+			{
+				Append(node);
+			}
+		}
+
+		public override void Clear()
+		{
+			while (Count > 0)
+			{
+				RemoveAtEnd();
+			}
+		}
+
+		// Default write methods will trigger TreeView visual updates.
+		// If you want to update vector content without notifying TreeViewNodes, use "core" version of the methods.
+		internal void InsertAtCore(int index, TreeViewNode node)
+		{
+			GetVectorInnerImpl().Insert(index, node);
+
+			// Keep SelectedItems and SelectedNodes in sync
+			var viewModel = m_viewModel;
+			if (viewModel != null)
+			{
+				var selectedItems = viewModel.SelectedItems;
+				if (selectedItems.Count != Count)
+				{
+					var listControl = viewModel.ListControl;
+					var item = listControl?.ItemFromNode(node);
+					if (item != null)
+					{
+						selectedItems.Insert(index, item);
+					}
+				}
+			}
+		}
+
+		internal void RemoveAtCore(int index)
+		{
+			GetVectorInnerImpl().RemoveAt(index);
+
+			// Keep SelectedItems and SelectedNodes in sync
+			var viewModel = m_viewModel;
+			if (viewModel != null)
+			{
+				var selectedItems = viewModel.SelectedItems;
+				if (Count != selectedItems.Count)
+				{
+					selectedItems.RemoveAt(index);
+				}
+			}
+		}
+	}
+}