wpf - WPF - 在 AllowDrop = False 时拖放期间跟踪鼠标
问题描述
我正在尝试创建一个在拖放操作期间将跟随鼠标的装饰器。即使鼠标拖动到 AllowDrop 设置为 False 的元素上,它也需要这样做。
问题:
- 在拖放期间不会触发普通鼠标事件(例如 MouseMove)
- 拖放事件(例如 DragOver、GiveFeedback)仅在有效的放置目标上触发(AllowDrop 设置为 true 的元素)
我需要跟踪:
- 鼠标在哪里
- 当鼠标移动时
如果没有上述任何事件,我找不到简单的方法来做到这一点。
我已经通过使用本机 GetCursorPos 方法解决了#1。这可以在我想要的任何时候可靠地获得鼠标的位置。
我剩下的问题是鼠标移动时得到通知。有什么方法可以在拖放操作期间获得鼠标移动通知,即使在将 AllowDrop 设置为 false 的元素上拖动时也是如此?
注意:我不想使用计时器而只是不断刷新位置(如果可以的话),我更愿意使用实际的鼠标输入。
解决方案
哇,没想到这一招这么狠。
我的第一次尝试是尝试绕过 WPF 并直接进入本机窗口消息泵。但事实证明,即使是标准的 WM_MOUSEMOVE 消息也不会在拖放操作期间通过。深入挖掘(通过 ole2.dll 源代码),我发现在拖动过程中创建了一个单独的、不可见的窗口,它吃掉了所有正常的消息,而是直接与放置目标交互(这可能是正常 WPF 鼠标事件的原因首先不要开火)。
我担心这可能会结束,直到我发现了hooks,它可以让你在消息被活动窗口消耗之前获取它们。使用 WH_MOUSE 钩子,我能够拦截 WM_MOUSEMOVE 消息并相应地放置我的 Adorner。
我不会在这里发布 Adorner 的所有代码,但我会给你我用来跟踪鼠标的 P/Invoke 代码:
Module NativeMethods
<DllImport("user32.dll")>
Public Function SetWindowsHookEx(ByVal idHook As HookType, ByVal lpfn As [Delegate], ByVal hInstance As IntPtr, ByVal threadId As Integer) As IntPtr
End Function
<DllImport("user32.dll")>
Public Function CallNextHookEx(ByVal hhk As IntPtr, ByVal nCode As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr
End Function
<DllImport("user32.dll")>
Public Function UnhookWindowsHookEx(ByVal hhk As IntPtr) As Boolean
End Function
<StructLayout(LayoutKind.Sequential)>
Friend Structure Win32Point
Public X As Int32
Public Y As Int32
Public Shared Widening Operator CType(Point As Win32Point) As Drawing.Point
Return New Drawing.Point(Point.X, Point.Y)
End Operator
Public Shared Widening Operator CType(Point As Win32Point) As Windows.Point
Return New Windows.Point(Point.X, Point.Y)
End Operator
End Structure
Const WM_MOUSEMOVE As Integer = 512
Enum HookType As Integer
WH_JOURNALRECORD = 0
WH_JOURNALPLAYBACK = 1
WH_KEYBOARD = 2
WH_GETMESSAGE = 3
WH_CALLWNDPROC = 4
WH_CBT = 5
WH_SYSMSGFILTER = 6
WH_MOUSE = 7
WH_HARDWARE = 8
WH_DEBUG = 9
WH_SHELL = 10
WH_FOREGROUNDIDLE = 11
WH_CALLWNDPROCRET = 12
WH_KEYBOARD_LL = 13
WH_MOUSE_LL = 14
End Enum
Public Delegate Function HookProc(ByVal code As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As Integer
<StructLayout(LayoutKind.Sequential)>
Structure MOUSEHOOKSTRUCT
Public pt As Win32Point
Public hwnd As IntPtr
Public wHitTestCode As UInteger
Public dwExtraInfo As IntPtr
End Structure
End Module
Class MouseTracker
Private HookHandle As IntPtr
Private HookDelegate As New HookProc(AddressOf NativeHook)
Private Sub AddNativeHook()
#Disable Warning BC40000 ' Type or member is obsolete
HookHandle = SetWindowsHookEx(HookType.WH_MOUSE, HookDelegate, IntPtr.Zero, AppDomain.GetCurrentThreadId())
#Enable Warning BC40000 ' Type or member is obsolete
End Sub
Private Sub RemoveNativeHook()
UnhookWindowsHookEx(HookHandle)
End Sub
Private Function NativeHook(code As Integer, wParam As IntPtr, lParam As IntPtr) As Integer
If code >= 0 Then
If wParam = WM_MOUSEMOVE Then
Dim data = Marshal.PtrToStructure(Of MOUSEHOOKSTRUCT)(lParam)
'From here you can use Visual.PointFromScreen(data.pt) to get the coordinates of the mouse relative to any WPF Visual.
'Then you do whatever you want with that!
End If
End If
Return CallNextHookEx(IntPtr.Zero, code, wParam, lParam)
End Function
End Class
如果您需要更多信息,我大量引用:
pinvoke.net:https
://pinvoke.net/default.aspx/user32/SetWindowsHookEx.html
Microsoft docs on hooks:https ://docs.microsoft.com/en-us/ windows/win32/winmsg/about-hooks
推荐阅读
- php - 该函数只处理最后寻找的模式。怎么了?
- python - 哪个是正确的标准差公式Python
- jelastic - Elasticsearch 容器为空
- ios - 如何在tableview中搜索数据?
- mongodb - 在 .FindOne 的 mongo-go-driver 中创建过滤器
- vba - 作为 ByRef 参数的类属性不起作用
- javascript - JS设置HTML元素的属性
- java - 在没有“WRITE_SETTINGS”权限的情况下单击图像时如何自动增加屏幕亮度
- postgrest - 使用 JSON 的 Postgrest OR 查询
- javascript - 针对 Web 开发的特定数据结构的建议