编写拖放装饰器的辅助方法

DeedyDesigner/Deedy.Activity/ActionViewer.cs

@@ -729,14 +729,7 @@ namespace Deedy.Activity
             if (eventSource is not ActionViewer && eventSource is DependencyObject dobj && this == dobj.FindAncestor<ActionViewer>()) result = true;
             return result;
         }
-        protected virtual void RemoveDragAdorner()
+
-        {
-            //TODO：移除拖拽装饰器
-        }
-        protected virtual void UpdateDragAdorner(Dock? dock)
-        {
-            //TODO：更新拖拽装饰器
-        }
         #region 订阅的交互事件
         protected override void OnDragEnter(DragEventArgs e)
         {
@@ -904,7 +897,7 @@ namespace Deedy.Activity
         /// 节点被选中
         /// </summary>
 		/// <remarks>
-        /// 节点被选中：当视图节点被选中时发生
+        /// 当视图节点被选中时发生
         /// </remarks>
         public static readonly RoutedEvent SelectedEvent = EventManager.RegisterRoutedEvent("Selected", RoutingStrategy.Bubble,
             typeof(EventHandler<RoutedEventArgs>), typeof(ActionViewer));

DeedyDesigner/Deedy.Activity/Adorner/DragPlacementAdorner.cs

@@ -0,0 +1,71 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Documents;
+using System.Windows.Media;
+
+namespace Deedy.Activity
+{
+    public class DragPlacementAdorner : Adorner
+    {
+        private static readonly Pen _PrevPen;
+        private static readonly Pen _NextPen;
+        private static readonly Pen _PartPen;
+        public Dock? Position { get; private set; }
+
+        static DragPlacementAdorner()
+        {
+            // 定义装饰器的画笔
+            _PrevPen = new Pen(Brushes.Red, 5.0);
+            _PrevPen.Freeze();
+            _NextPen = new Pen(Brushes.Red, 5.0);
+            _NextPen.Freeze();
+            _PartPen = new Pen(Brushes.Blue, 3.0);
+            _PartPen.Freeze();
+        }
+
+        public DragPlacementAdorner(UIElement adornedElement, Dock? dock) : base(adornedElement)
+        {
+            this.Position = dock;
+            IsHitTestVisible = false;
+        }
+
+        protected override void OnRender(DrawingContext drawingContext)
+        {
+            var adornedElementRect = new Rect(AdornedElement.RenderSize);
+
+            // 根据位置信息绘制不同的视觉效果
+            switch (this.Position)
+            {
+                case Dock.Top:
+                    drawingContext.DrawLine(_PrevPen,
+                        new Point(0, 0),
+                        new Point(adornedElementRect.Right, 0));
+                    break;
+                case Dock.Bottom:
+                    drawingContext.DrawLine(_NextPen,
+                        new Point(0, adornedElementRect.Bottom),
+                        new Point(adornedElementRect.Right, adornedElementRect.Bottom));
+                    break;
+                case Dock.Left:
+                    drawingContext.DrawLine(_PrevPen,
+                        new Point(0, 0),
+                        new Point(0, adornedElementRect.Bottom));
+                    break;
+                case Dock.Right:
+                    drawingContext.DrawLine(_NextPen,
+                        new Point(adornedElementRect.Right, 0),
+                        new Point(adornedElementRect.Right, adornedElementRect.Bottom));
+                    break;
+                case null:
+                    drawingContext.DrawRectangle(null, _PartPen, adornedElementRect);
+                    break;
+                default: break;
+            }
+        }
+    }
+}

DeedyDesigner/Deedy.Activity/Helper.cs

@@ -7,6 +7,9 @@ using System.Threading.Tasks;
 using System.Windows.Media;
 using System.Windows;
 using System.Runtime.CompilerServices;
+using System.Windows.Controls;
+using System.Windows.Documents;
+using System.Collections.Concurrent;
 
 namespace Deedy.Activity
 {
@@ -299,5 +302,51 @@ namespace Deedy.Activity
         }
         [UnsafeAccessor(UnsafeAccessorKind.Method, Name = "set_ParentElement")]
         private static extern void ActionSetter_ParentElement(BasalAction action, IElement? value);
+        /// <summary>
+        /// 拖放装饰层的集合
+        /// </summary>
+        private readonly static ConcurrentDictionary<UIElement, AdornerLayer> AdornerLayers = new();
+        /// <summary>
+        /// 拖放装饰器的集合
+        /// </summary>
+        private readonly static ConcurrentDictionary<UIElement, DragPlacementAdorner> DragAdorners = new();
+        /// <summary>
+        /// 移除一个「UIElement」上的拖放装饰器
+        /// </summary>
+        /// <param name="viewer">目标「UIElement」对象</param>
+        public static void RemoveDragAdorner(this UIElement viewer)
+        {
+            if (viewer is null) return;
+            AdornerLayers.Remove(viewer, out var _AdornerLayer);
+            DragAdorners.Remove(viewer, out var _DragAdorner);
+
+            if (_AdornerLayer != null && _DragAdorner != null)
+                _AdornerLayer.Remove(_DragAdorner);
+
+            if (_AdornerLayer != null) _AdornerLayer = null;
+            if (_DragAdorner != null) _DragAdorner = null;
+        }
+        /// <summary>
+        /// 更新一个「UIElement」上的拖放装饰器
+        /// </summary>
+        /// <param name="viewer">目标「UIElement」对象</param>
+        /// <param name="dock">画线位置，「null」表示画4面框线</param>
+        public static void UpdateDragAdorner(this UIElement viewer, Dock? dock)
+        {
+            if (viewer is null) return;
+            AdornerLayers.Remove(viewer, out var _AdornerLayer);
+            DragAdorners.Remove(viewer, out var _DragAdorner);
+
+            if (_AdornerLayer != null && _DragAdorner != null)
+                _AdornerLayer.Remove(_DragAdorner);
+
+            _AdornerLayer ??= AdornerLayer.GetAdornerLayer(viewer);
+            if (_AdornerLayer is null) return;
+            _DragAdorner = new DragPlacementAdorner(viewer, dock);
+            _AdornerLayer.Add(_DragAdorner);
+
+            AdornerLayers.TryAdd(viewer, _AdornerLayer);
+            DragAdorners.TryAdd(viewer, _DragAdorner);
+        }
     }
 }