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拖动时显示 ListView 项目

　　这段代码演示了如何利用 ImageList 函数在拖动 ListView 项目的时候显示被拖动的项目图标（就像在资源管理器中所看到的那样）。

Option Explicit

注释： ==== Private members ====
Private m_lIL As Long
Private m_lWndPrev As Long
Private m_lTimer As Long

注释： ==== API declarations ====

Private Declare Function ImageList_BeginDrag Lib "comctl32" ( _
   ByVal himlTrack As Long, _
   ByVal iTrack As Long, _
   ByVal dxHotspot As Long, _
   ByVal dyHotspot As Long) As Long
   
Private Declare Sub ImageList_EndDrag Lib "comctl32" ()

Private Declare Function ImageList_DragEnter Lib "comctl32" ( _
   ByVal hwndLock As Long, _
   ByVal X As Long, _
   ByVal Y As Long) As Long

Private Declare Function ImageList_DragLeave Lib "comctl32" ( _
   ByVal hwndLock As Long) As Long

Private Declare Function ImageList_DragMove Lib "comctl32" ( _
   ByVal X As Long, _
   ByVal Y As Long) As Long

Private Declare Function ImageList_Destroy Lib "comctl32" ( _
   ByVal himl As Long) As Long

Private Type POINTL
   X As Long
   Y As Long
End Type

Private Declare Function GetCursorPos Lib "user32" ( _
   lpPoint As POINTL) As Long
   
Private Declare Function WindowFromPoint Lib "user32" ( _
   ByVal xPoint As Long, _
   ByVal yPoint As Long) As Long

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" ( _
   ByVal hWnd As Long, _
   ByVal wMsg As Long, _
   ByVal wParam As Long, _
   lParam As Any) As Long

Const LVM_CREATEDRAGIMAGE = &H1000& + 33

Private Type RECT
   Left As Long
   Top As Long
   Right As Long
   Bottom As Long
End Type

Private Declare Function GetWindowRect Lib "user32" ( _
   ByVal hWnd As Long, _
   lpRect As RECT) As Long

Private Declare Function KillTimer Lib "user32" ( _
   ByVal hWnd As Long, _
   ByVal nIDEvent As Long) As Long
   
Private Declare Function SetTimer Lib "user32" ( _
   ByVal hWnd As Long, _
   ByVal nIDEvent As Long, _
   ByVal uElapse As Long, _
   ByVal lpTimerFunc As Long) As Long

注释：
注释： DragComplete
注释：
注释： Removes the drag image
注释：
Public Sub ListViewDragComplete()
   
   注释： Stop the timer
   KillTimer 0, m_lTimer

   注释： End the image dragging
   ImageList_EndDrag
   
   注释： Destroy the ImageList
   ImageList_Destroy m_lIL
   
End Sub

注释：
注释： ListViewStartDrag
注释：
注释： Starts the image dragging
注释：
注释： Parameters:
注释： hWndListView - Window handle of the ListView that
注释：                contains the item to drag
注释： ItemIndex - Index of the item to drag
注释： X, Y - Hot spot coordinates in the image
注释：
Public Sub ListViewStartDrag( _
   ByVal hWndListView As Long, _
   ByVal ItemIndex As Long, _
   Optional ByVal X As Long = 20, _
   Optional ByVal Y As Long = 20)
Dim tPoint As POINTL

   注释： Get a ImageList with
   注释： the drag image
   m_lIL = SendMessage(hWndListView, LVM_CREATEDRAGIMAGE, ItemIndex - 1, tPoint)
   
   注释： Start the image dragging
   ImageList_BeginDrag m_lIL, 0, X, Y
   
   注释： Start the timer
   m_lTimer = SetTimer(0, 0, 1, AddressOf TimerDragMove)

End Sub

Private Sub TimerDragMove( _
   ByVal hWnd As Long, _
   ByVal uMsg As Long, _
   ByVal idEvent As Long, _
   ByVal dwTime As Long)
Dim tPoint As POINTL
Dim tRect As RECT
Dim lWnd As Long
   
   注释： Get the cursor position
   GetCursorPos tPoint
   
   注释： Get the window under
   注释： the cursor
   lWnd = WindowFromPoint(tPoint.X, tPoint.Y)
   
   注释： Check if the cursor has moved
   If lWnd <>  m_lWndPrev Then
   
      注释： Remove the image from
      注释： the previous window
      ImageList_DragLeave m_lWndPrev
      
      注释： Add the image to
      注释： the new window
      ImageList_DragEnter lWnd, 0, 0
      
      注释： Save the current window
      m_lWndPrev = lWnd
      
   End If
   
   注释： Get the window rectangle
   GetWindowRect lWnd, tRect
   
   注释： Convert the screen coordinates
   注释： to window coordinates
   tPoint.X = tPoint.X - tRect.Left
   tPoint.Y = tPoint.Y - tRect.Top
   
   注释： Move the image
   ImageList_DragMove tPoint.X, tPoint.Y
   
End Sub
在 OLEStartDrag 事件代码中调用 ListViewStartDrag：


Private Sub ListView1_OLEStartDrag( _
   Data As ComctlLib.DataObject, _
   AllowedEffects As Long)
   
   ListViewStartDrag ListView1.hWnd, ListView1.SelectedItem.Index

End Sub
同时在 OLECompleteDrag 事件代码中调用 ListViewDragComplete：


Private Sub ListView1_OLECompleteDrag(Effect As Long)
   
   ListViewDragComplete
   
End Sub