by Angsuman Banerji (23 Submissions)
Category: Windows API Call/Explanation
Compatability: VB 6.0
Difficulty: Unknown Difficulty
Originally Published: Fri 4th January 2008
Date Added: Mon 8th February 2021
Rating: 
(1 Votes)
Enumerating Windows Using the API
API Declarations
ByVal lpEnumFunc As Long, _
ByVal lparam As Long _
) As Long
Public Declare Function IsWindowVisible Lib "user32" ( _
ByVal hwnd As Long) As Long
Public Declare Function GetWindowText Lib "user32" _
Alias "GetWindowTextA" ( _
ByVal hwnd As Long, _
ByVal lpString As String, _
ByVal cch As Long _
) As Long
Public Declare Function GetWindowTextLength Lib "user32" _
Alias "GetWindowTextLengthA" ( _
ByVal hwnd As Long _
) As Long
Public Declare Function GetClassName Lib "user32" _
Alias "GetClassNameA" ( _
ByVal hwnd As Long, _
ByVal lpClassName As String, _
ByVal nMaxCount As Long _
) As Long
VBcoders
Private m_cSink As IEnumWindowsSink
Private Function EnumWindowsProc( _
ByVal hwnd As Long, _
ByVal lparam As Long _
) As Long
Dim bStop As Boolean
bStop = False
m_cSink.EnumWindow hwnd, bStop
If (bStop) Then
EnumWindowsProc = 0
Else
EnumWindowsProc = 1
End If
End Function
Public Function EnumerateWindows( _
ByRef cSink As IEnumWindowsSink _
) As Boolean
If Not (m_cSink Is Nothing) Then
Exit Function
End If
Set m_cSink = cSink
EnumWindows AddressOf EnumWindowsProc, cSink.Identifier
Set m_cSink = Nothing
End Function
'You are now in a position to use this from any form or class. By telling the
'form/class to implement the IEnumWindowsSink methods, VB will automatically
'put the EnumWindow sub and Identifier Property Get into the code, requiring
'you to code them. Here is a sample showing how to find all the Windows on the
'system from a form. The items are placed into a ListView control called
'lvwWindows with 4 columns:
Implements IEnumWindowsSink
Private Sub IEnumWindowsSink_EnumWindow( _
ByVal hwnd As Long, _
bStop As Boolean _
)
Dim itmX As ListItem
Set itmX = lvwWindows.ListItems.Add(, , WindowTitle(hwnd))
itmX.SubItems(1) = ClassName(hwnd)
itmX.SubItems(2) = hwnd
itmX.SubItems(3) = IsWindowVisible(hwnd)
End Sub
Private Property Get IEnumWindowsSink_Identifier() As Long
IEnumWindowsSink_Identifier = Me.hwnd
End Property
'The definitions of the functions to get a Window's title, class and
'visibility from a hWnd are as follows:
Public Function WindowTitle(ByVal lHwnd As Long) As String
Dim lLen As Long
Dim sBuf As String
' Get the Window Title:
lLen = GetWindowTextLength(lHwnd)
If (lLen > 0) Then
sBuf = String$(lLen + 1, 0)
lLen = GetWindowText(lHwnd, sBuf, lLen + 1)
WindowTitle = Left$(sBuf, lLen)
End If
End Function
Public Function ClassName(ByVal lHwnd As Long) As String
Dim lLen As Long
Dim sBuf As String
lLen = 260
sBuf = String$(lLen, 0)
lLen = GetClassName(lHwnd, sBuf, lLen)
If (lLen <> 0) Then
ClassName = Left$(sBuf, lLen)
End If
End Function
