Merge pull request unoplatform#14616 from TopProgrammer77/TreeView_Dr…

…agItemsCompleted

fix(TreeView): raise DragItemsCompleted when dragging items is completed

src/SamplesApp/SamplesApp.UITests/Windows_UI_Xaml/DragAndDropTests/DragDrop_TreeView_Reorder_Automated.cs

@@ -5,6 +5,7 @@
 using Uno.UITest.Helpers.Queries;
 using System.Linq;
 using System;
+using System.Threading.Tasks;
 
 namespace SamplesApp.UITests.Windows_UI_Xaml.DragAndDropTests
 {
@@ -25,6 +26,10 @@ public void When_Dragging_TreeView_Item()
 			var bt2 = _app.Marked("bt2");
 			var bt3 = _app.Marked("bt3");
 			var focusbt = _app.Marked("focusbt");
+			var radio_disable = _app.Marked("radio_disable");
+
+			_app.WaitForElement(radio_disable);
+			_app.Tap(radio_disable);
 
 			_app.WaitForElement(tv);
 			_app.Tap(bt1);
@@ -64,5 +69,34 @@ public void When_Dragging_TreeView_Item()
 			result = _app.Screenshot("result3");
 			ImageAssert.AreEqual(case3, result);
 		}
+
+		[Test]
+		[AutoRetry]
+		[ActivePlatforms(Platform.Browser)]
+		public void When_OnDragItemsCompleted()
+		{
+			Run("UITests.Windows_UI_Xaml.DragAndDrop.DragDrop_TreeView", skipInitialScreenshot: true);
+			var tv = _app.Marked("tv");
+			var bt0 = _app.Marked("bt0");
+			var radio_enable = _app.Marked("radio_enable");
+			var tb = _app.Marked("tb");
+
+			_app.WaitForElement(tv);
+
+			_app.WaitForElement(radio_enable);
+			_app.Tap(radio_enable);
+			_app.WaitForElement(bt0);
+			_app.Tap(bt0);
+
+			var tvBounds = _app.Query("tv").Single().Rect;
+			float fromX = tvBounds.X + 100;
+			float fromY = tvBounds.Y + _itemHeight * 3 + _offset;
+			float toX = tvBounds.X + 100;
+			float toY = tvBounds.Y + _offset;
+			_app.DragCoordinates(fromX, fromY, toX, toY);
+
+			string text = _app.GetText("tb").Trim();
+			Assert.AreEqual("DragItemsCompleted is triggered", text);
+		}
 	}
 }

src/SamplesApp/UITests.Shared/Windows_UI_Xaml/DragAndDrop/DragDrop_TreeView.xaml

@@ -24,5 +24,8 @@
 		<Button x:Name="bt2" Content="case2"/>
 		<Button x:Name="bt3" Content="case3"/>
 		<Button x:Name="focusbt" Content="focus"/>
+		<RadioButton x:Name="radio_disable" GroupName="radio" Content="Disable TextBox"/>
+		<RadioButton x:Name="radio_enable" GroupName="radio" Content="Enable TextBox"/>
+		<TextBlock x:Name="tb" Visibility="Collapsed"/>
 	</StackPanel>
 </Page>

src/SamplesApp/UITests.Shared/Windows_UI_Xaml/DragAndDrop/DragDrop_TreeView.xaml.cs

@@ -124,6 +124,22 @@ public DragDrop_TreeView()
 				});
 			};
 
+			tv.DragItemsCompleted += (s, e) =>
+			{
+				tb.Text = "DragItemsCompleted is triggered";
+			};
+
+			radio_disable.Checked += (s, e) =>
+			{
+				tb.Visibility = Microsoft.UI.Xaml.Visibility.Collapsed;
+			};
+
+			radio_enable.Checked += (s, e) =>
+			{
+				tb.Visibility = Microsoft.UI.Xaml.Visibility.Visible;
+			};
+
+			radio_disable.IsChecked = true;
 		}
 	}
 }

src/Uno.UI/UI/Xaml/Controls/ListViewBase/ListViewBase.DragDrop.cs

@@ -96,11 +96,9 @@ private static void PrepareContainerForDragDropCore(UIElement itemContainer)
 			// Known issue: the ContainerClearedForItem might not be invoked properly for all items on some platforms.
 			// This patch is acceptable as event handlers are static (so they won't leak).
 			itemContainer.DragStarting -= OnItemContainerDragStarting;
-			itemContainer.DropCompleted -= OnItemContainerDragCompleted;
 
 			itemContainer.CanDrag = true;
 			itemContainer.DragStarting += OnItemContainerDragStarting;
-			itemContainer.DropCompleted += OnItemContainerDragCompleted;
 		}
 
 		private static void ClearContainerForDragDrop(UIElement itemContainer)
@@ -112,7 +110,6 @@ private static void ClearContainerForDragDrop(UIElement itemContainer)
 
 			itemContainer.CanDrag = false;
 			itemContainer.DragStarting -= OnItemContainerDragStarting;
-			itemContainer.DropCompleted -= OnItemContainerDragCompleted;
 
 			itemContainer.DragEnter -= OnReorderDragUpdated;
 			itemContainer.DragOver -= OnReorderDragUpdated;
@@ -124,6 +121,9 @@ private static void OnItemContainerDragStarting(UIElement sender, DragStartingEv
 		{
 			if (ItemsControlFromItemContainer(sender) is ListViewBase that && that.CanDragItems)
 			{
+				// only raise DragItemsCompleted if DragItemsStarting was raised
+				sender.DropCompleted -= OnItemContainerDragCompleted;
+				sender.DropCompleted += OnItemContainerDragCompleted;
 				// The items contains all selected items ONLY if the draggedItem is selected.
 				var draggedItem = that.ItemFromContainer(sender);
 				var items =
@@ -166,6 +166,7 @@ private static void OnItemContainerDragStarting(UIElement sender, DragStartingEv
 					that.ChangeSelectorItemsVisualState(true);
 				}
 			}
+
 		}
 
 		private static void OnItemContainerDragCompleted(UIElement sender, DropCompletedEventArgs innerArgs)
@@ -191,6 +192,7 @@ private static void OnItemContainerDragCompleted(UIElement sender, DropCompleted
 				// (eg if drag was released outside bounds of list)
 				that.CleanupReordering();
 			}
+			sender.DropCompleted -= OnItemContainerDragCompleted;
 		}
 
 		private static void OnReorderDragUpdated(object sender, _DragEventArgs dragEventArgs)