解决Popup StayOpen=true时，永远置顶的问题

前言

Popup显示时会置顶显示。尤其是 Popup设置了StayOpen=true时，会一直置顶显示，问题更明显。

置顶显示问题现象：

解决方案

怎么解决问题？

获取绑定UserControl所在的窗口，窗口层级变化时，通知更新当前Popup的Tostmost属性。

1. 添加附加属性

在属性变更中，监听Loaded/UnLoaded事件，在加载后处理相应的逻辑。

         private static readonly DependencyProperty TopmostInCurrentWindowProperty = DependencyProperty.RegisterAttached("TopmostInCurrentWindow",
             typeof(bool), typeof(Popup), new FrameworkPropertyMetadata(false, OnTopmostInCurrentWindowChanged));

         public static bool GetTopmostInCurrentWindow(DependencyObject obj)
         {
             return (bool)obj.GetValue(TopmostInCurrentWindowProperty);
         }

         public static void SetTopmostInCurrentWindow(DependencyObject obj, bool value)
         {
             obj.SetValue(TopmostInCurrentWindowProperty, value);
         }

         private static void OnTopmostInCurrentWindowChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
         {
             if (d is Popup popup)
             {
                 _popup = popup;
                 popup.Loaded -= OnPopupLoaded;
                 popup.Unloaded -= OnPopupUnloaded;
                 if ((bool)e.NewValue)
                 {
                     popup.Loaded += OnPopupLoaded;
                     popup.Unloaded += OnPopupUnloaded;
                 }
             }
         }

2. 添加事件监听

• 在Popup.Loaded事件中，监听Popup所在窗口的唤醒事件。同时,Unloaded事件中注销所在窗口的事件监听。
• 在窗口唤醒事件监听逻辑中，设置当前popup选择性的置顶显示
• 添加Popup的MouseDown事件监听，点击Popup的内容后，Popup置顶显示、窗口层级也发相应的变化。

        static void OnPopupLoaded(object sender, RoutedEventArgs e)
         {
             if (!(sender is Popup popup))
                 return;

             popup.Child?.AddHandler(UIElement.PreviewMouseLeftButtonDownEvent, new MouseButtonEventHandler(OnChildPreviewMouseLeftButtonDown), true);

             _parentWindow = Window.GetWindow(popup);
             if (_parentWindow == null)
                 return;

             _parentWindow.Activated -= OnParentWindowActivated;
             _parentWindow.Deactivated -= OnParentWindowDeactivated;
             _parentWindow.Activated += OnParentWindowActivated;
             _parentWindow.Deactivated += OnParentWindowDeactivated;
         }

         static void OnPopupUnloaded(object sender, RoutedEventArgs e)
         {
             if (_parentWindow == null)
                 return;
             _parentWindow.Activated -= OnParentWindowActivated;
             _parentWindow.Deactivated -= OnParentWindowDeactivated;
         }

         private static void OnParentWindowActivated(object sender, EventArgs e)
         {
             SetTopmostState(true);
         }

         private static void OnParentWindowDeactivated(object sender, EventArgs e)
         {
             //Parent Window Deactivated
             if (IsTopmost == false)
             {
                 SetTopmostState(IsTopmost);
             }
         }

         static void OnChildPreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
         {
             SetTopmostState(true);

             if (!_parentWindow.IsActive && IsTopmost == false)
             {
                 _parentWindow.Activate();
             }
         }

3. 选择性置顶显示

• 记录/设置当前Popup的置顶显示状态
• 选择性置顶显示-可以显示在最顶层，也可以只显示在当前窗口的上层。

         private static bool IsTopmost
         {
             get => _isTopmost;
             set
             {
                 _isTopmost = value;
                 SetTopmostState(value);
             }
         }

         private static void SetTopmostState(bool isTop)
         {
             if (_appliedTopMost.HasValue && _appliedTopMost == isTop)
             {
                 return;
             }

             if (_popup?.Child == null)
                 return;

             var hwndSource = (PresentationSource.FromVisual(_popup.Child)) as HwndSource;

             if (hwndSource == null)
                 return;
             var hwnd = hwndSource.Handle;

             RECT rect;

             if (!GetWindowRect(hwnd, out rect))
                 return;

             if (isTop)
             {
                 SetWindowPos(hwnd, HWND_TOPMOST, rect.Left, rect.Top, (int)_popup.Width, (int)_popup.Height, TOPMOST_FLAGS);
             }
             else
             {
                 // 重新激活Topmost，需要bottom->top->notop
                 SetWindowPos(hwnd, HWND_BOTTOM, rect.Left, rect.Top, (int)_popup.Width, (int)_popup.Height, TOPMOST_FLAGS);
                 SetWindowPos(hwnd, HWND_TOP, rect.Left, rect.Top, (int)_popup.Width, (int)_popup.Height, TOPMOST_FLAGS);
                 SetWindowPos(hwnd, HWND_NOTOPMOST, rect.Left, rect.Top, (int)_popup.Width, (int)_popup.Height, TOPMOST_FLAGS);
             }

             _appliedTopMost = isTop;
         }

以下是窗口消息处理、私有字段：

通过user32.dll的GetWindowRect和SetWindowPos函数，处理Popup层级问题

         #region 窗口消息

         [StructLayout(LayoutKind.Sequential)]
         public struct RECT

         {
             public int Left;
             public int Top;
             public int Right;
             public int Bottom;
         }

         [DllImport("user32.dll")]
         [return: MarshalAs(UnmanagedType.Bool)]
         private static extern bool GetWindowRect(IntPtr hWnd, out RECT lpRect);

         [DllImport("user32.dll")]
         private static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, uint uFlags);

         static readonly IntPtr HWND_TOPMOST = new IntPtr(-);
         static readonly IntPtr HWND_NOTOPMOST = new IntPtr(-);
         static readonly IntPtr HWND_TOP = new IntPtr();
         static readonly IntPtr HWND_BOTTOM = new IntPtr();

         private const UInt32 SWP_NOSIZE = 0x0001;
         const UInt32 SWP_NOMOVE = 0x0002;
         const UInt32 SWP_NOREDRAW = 0x0008;
         const UInt32 SWP_NOACTIVATE = 0x0010;

         const UInt32 SWP_NOOWNERZORDER = 0x0200;
         const UInt32 SWP_NOSENDCHANGING = 0x0400;

         //很重要，窗口切换等需要将popup显示层级重新刷新
         const UInt32 TOPMOST_FLAGS =
             SWP_NOACTIVATE | SWP_NOOWNERZORDER | SWP_NOSIZE | SWP_NOMOVE | SWP_NOREDRAW | SWP_NOSENDCHANGING;

         #endregion

         #region private fileds

         private static bool? _appliedTopMost;
         private static bool _alreadyLoaded;
         private static Window _parentWindow;
         private static Popup _popup;
         private static bool _isTopmost;

         #endregion

下载 此Demo

注：也可以通过自定义用户控件Popup实现，逻辑一样：

     /// <summary>
     /// 解决StayOpen=true时，永远置顶的问题
     /// </summary>
     public class MyPopup : Popup
     {
         public static readonly DependencyProperty IsTopmostProperty = DependencyProperty.Register("IsTopmost", typeof(bool), typeof(MyPopup), new FrameworkPropertyMetadata(false, OnIsTopmostChanged));

         private bool? _appliedTopMost;
         private bool _alreadyLoaded;
         private Window _parentWindow;

         public bool IsTopmost
         {
             get { return (bool)GetValue(IsTopmostProperty); }
             set { SetValue(IsTopmostProperty, value); }
         }

         /// <summary>
         /// ctor
         /// </summary>
         public MyPopup()
         {
             Loaded += OnPopupLoaded;
             Unloaded += OnPopupUnloaded;
         }

         void OnPopupLoaded(object sender, RoutedEventArgs e)
         {
             if (_alreadyLoaded)
                 return;

             _alreadyLoaded = true;

             if (Child != null)
             {
                 Child.AddHandler(PreviewMouseLeftButtonDownEvent, new MouseButtonEventHandler(OnChildPreviewMouseLeftButtonDown), true);
             }

             _parentWindow = Window.GetWindow(this);

             if (_parentWindow == null)
                 return;

             _parentWindow.Activated += OnParentWindowActivated;
             _parentWindow.Deactivated += OnParentWindowDeactivated;
         }

         private void OnPopupUnloaded(object sender, RoutedEventArgs e)
         {
             if (_parentWindow == null)
                 return;
             _parentWindow.Activated -= OnParentWindowActivated;
             _parentWindow.Deactivated -= OnParentWindowDeactivated;
         }

         void OnParentWindowActivated(object sender, EventArgs e)
         {
             SetTopmostState(true);
         }

         void OnParentWindowDeactivated(object sender, EventArgs e)
         {
             Debug.WriteLine("Parent Window Deactivated");

             if (IsTopmost == false)
             {
                 SetTopmostState(IsTopmost);
             }
         }

         void OnChildPreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
         {

             SetTopmostState(true);

             if (!_parentWindow.IsActive && IsTopmost == false)
             {
                 _parentWindow.Activate();
             }
         }

         private static void OnIsTopmostChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
         {
             var thisobj = (MyPopup)obj;

             thisobj.SetTopmostState(thisobj.IsTopmost);
         }

         protected override void OnOpened(EventArgs e)
         {
             SetTopmostState(IsTopmost);
             base.OnOpened(e);
         }

         private void SetTopmostState(bool isTop)
         {
             if (_appliedTopMost.HasValue && _appliedTopMost == isTop)
             {
                 return;
             }

             if (Child == null)
                 return;

             var hwndSource = (PresentationSource.FromVisual(Child)) as HwndSource;

             if (hwndSource == null)
                 return;
             var hwnd = hwndSource.Handle;

             RECT rect;

             if (!GetWindowRect(hwnd, out rect))
                 return;

             if (isTop)
             {
                 SetWindowPos(hwnd, HWND_TOPMOST, rect.Left, rect.Top, (int)Width, (int)Height, TOPMOST_FLAGS);
             }
             else
             {
                 // 重新激活Topmost，需要bottom->top->notop
                 SetWindowPos(hwnd, HWND_BOTTOM, rect.Left, rect.Top, (int)Width, (int)Height, TOPMOST_FLAGS);
                 SetWindowPos(hwnd, HWND_TOP, rect.Left, rect.Top, (int)Width, (int)Height, TOPMOST_FLAGS);
                 SetWindowPos(hwnd, HWND_NOTOPMOST, rect.Left, rect.Top, (int)Width, (int)Height, TOPMOST_FLAGS);
             }

             _appliedTopMost = isTop;
         }

         [StructLayout(LayoutKind.Sequential)]
         public struct RECT

         {
             public int Left;
             public int Top;
             public int Right;
             public int Bottom;
         }

         [DllImport("user32.dll")]
         [return: MarshalAs(UnmanagedType.Bool)]
         private static extern bool GetWindowRect(IntPtr hWnd, out RECT lpRect);

         [DllImport("user32.dll")]
         private static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X,
         int Y, int cx, int cy, uint uFlags);

         static readonly IntPtr HWND_TOPMOST = new IntPtr(-);
         static readonly IntPtr HWND_NOTOPMOST = new IntPtr(-);
         static readonly IntPtr HWND_TOP = new IntPtr();
         static readonly IntPtr HWND_BOTTOM = new IntPtr();

         private const UInt32 SWP_NOSIZE = 0x0001;
         const UInt32 SWP_NOMOVE = 0x0002;
         const UInt32 SWP_NOZORDER = 0x0004;
         const UInt32 SWP_NOREDRAW = 0x0008;
         const UInt32 SWP_NOACTIVATE = 0x0010;

         const UInt32 SWP_FRAMECHANGED = 0x0020; /* The frame changed: send WM_NCCALCSIZE */
         const UInt32 SWP_SHOWWINDOW = 0x0040;
         const UInt32 SWP_HIDEWINDOW = 0x0080;
         const UInt32 SWP_NOCOPYBITS = 0x0100;
         const UInt32 SWP_NOOWNERZORDER = 0x0200; /* Don’t do owner Z ordering */
         const UInt32 SWP_NOSENDCHANGING = 0x0400; /* Don’t send WM_WINDOWPOSCHANGING */

         //很重要，窗口切换等需要将popup显示层级重新刷新
         const UInt32 TOPMOST_FLAGS =
         SWP_NOACTIVATE | SWP_NOOWNERZORDER | SWP_NOSIZE | SWP_NOMOVE | SWP_NOREDRAW | SWP_NOSENDCHANGING;
     }

解决方案总结

添加如上附加属性或者用户控件Popup后，能解决置顶问题，Popup只会出现在所在窗口上层。

截图如下：