VB Forum / Win API / March 2008

Good Evening,

I'm developing a Visual Basic program to control another program
written in Visual C++.
The Visual C++ program is composed of four SysListView32 objects.
I can retrieve the handles of these controls and many messages works
greatly except the LVM_SETITEMSTATE one.
When I use this kind of message the Visual C++ application randomly
returns a fatal error about the file COMCTL32.OCX and hangs up! In the
same folder of Visual C++ executable file there is a file named
COMCTL32.OCX .
I said "randomly" because in other cases nothing happens but I don't
get the fatal error and in a very little number of cases I can select
all the elements of only one SysListView of four.

The code:

Type LVITEM
   mask As Long
   iItem As Long
   iSubItem As Long
   state As Long
   stateMask As Long
   pszText As Long
   cchTextMax As Long
   iImage As Long
   lParam As Long
   iIndent As Long
End Type

Private Const LVM_FIRST = &H1000
Private Const LVM_SETITEMSTATE = (LVM_FIRST + 43)
Private Const LVIS_SELECTED = &H2
Private Const LVIF_STATE = &H8

Public hSysListView32(3) As Long 'handles of SysListView32
Public SysListAttrib(3) As LVITEM

Sub TestButton()
   hFound = FindWindowEx(0, 0, vbNullString, "Visual C++ Program")

   If hFound > 0 Then
       result = EnumChildWindows(hFound, AddressOf EnumChildProc,
ByVal 0&)
   End If
End Sub

Public Function EnumChildProc(ByVal hwnd As Long, ByVal lParam As
Long) As Long
   Dim sClass As String
   Dim ret&

   Static i As Integer

   sClass = Space$(64)
   ret = GetClassName(hwnd, sClass, 64)

   If InStr(Left(sClass, ret), "SysListView32") Then

           hSysListView32(i) = hwnd

       i = i + 1
   End If

   EnumChildProc = 1
End Function

Sub Select() 'called by a button on the form

   Dim x

   For x = 0 To 3

       SysListAttrib(x).mask = LVIF_STATE
       SysListAttrib(x).state = True
       SysListAttrib(x).stateMask = LVIS_SELECTED

           Call SendMessage(hSysListView32(x), LVM_SETITEMSTATE, -1,
SysListAttrib(x))
           Call UpdateWindow(hSysListView32(x))
   Next x

End Sub

Thank you so much, Emilio.