Binaryworld - Get the List of all the Active Tasks ... [ VB -> Thread-Process ]

API Declarations

Option Explicit

' API Constants
Const WS_MINIMIZE = &H20000000 ' Style bit 'is minimized'
Const HWND_TOP = 0 ' Move to top of z-order
Const SWP_NOSIZE = &H1 ' Do not re-size window
Const SWP_NOMOVE = &H2 ' Do not reposition window
Const SWP_SHOWWINDOW = &H40 ' Make window visible/active
Const GW_HWNDFIRST = 0 ' Get first Window handle
Const GW_HWNDNEXT = 2 ' Get next window handle
Const GWL_STYLE = (-16) ' Get Window's style bits
Const SW_RESTORE = 9 ' Restore window

' The following constants will be combined to define properties
' of a 'normal' task top-level window. Any window with ' these set will be
' included in the list:
Const WS_VISIBLE = &H10000000 ' Window is not hidden
Const WS_BORDER = &H800000 ' Window has a border
' Other bits that are normally set include:
Const WS_CLIPSIBLINGS = &H4000000 ' can clip windows
Const WS_THICKFRAME = &H40000 ' Window has thick border
Const WS_GROUP = &H20000 ' Window is top of group
Const WS_TABSTOP = &H10000 ' Window has tabstop

' API Functions Definition
Private Declare Function GetWindow Lib "user32.dll" (ByVal hWnd As Long, ByVal wCmd As Long) As Long
Private Declare Function GetWindowWord Lib "user32.dll" (ByVal hWnd As Long, ByVal nIndex As Long) As Integer
Private Declare Function GetWindowLong Lib "user32.dll" Alias "GetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long) As Long
Private Declare Function GetWindowText Lib "user32.dll" Alias "GetWindowTextA" (ByVal hWnd As Long, ByVal lpString As String, ByVal cch As Long) As Long
Private Declare Function GetWindowTextLength Lib "user32.dll" Alias "GetWindowTextLengthA" (ByVal hWnd As Long) As Long
Private Declare Function SetWindowPos Lib "user32.dll" (ByVal hWnd As Long, ByVal hWndInsertAfter As Long, ByVal x As Long, ByVal y As Long, ByVal cx As Long, ByVal cy As Long, ByVal wFlags As Long) As Long
Private Declare Function ShowWindow Lib "user32.dll" (ByVal hWnd As Long, ByVal nCmdShow As Long) As Long

Module

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' Public Task Item Structure
Public Type TASK_STRUCT
  TaskName As String
  TaskID As Long
End Type

'Structure filled by FillTaskList Sub call
Public TaskList(1000) As TASK_STRUCT
Public NumTasks As Long

' Returns if a Process is a Visible Window
Public Function IsTask(hwndTask As Long) As Boolean
  Dim WndStyle As Long
  Const IsTaskStyle = WS_VISIBLE Or WS_BORDER

  WndStyle = GetWindowLong(hwndTask, GWL_STYLE)
  If (WndStyle And IsTaskStyle) = IsTaskStyle Then IsTask = True
End Function

' Fills the Task structure with captions and hWnd of all active programs
Public Sub FillTaskList(hWnd As Long)
  Dim hwndTask As Long
  Dim intLen As Long
  Dim strTitle As String
  Dim cnt As Integer

  cnt = 0
  ' process all top-level windows in master window list
  hwndTask = GetWindow(hWnd, GW_HWNDFIRST) ' get first window
  Do While hwndTask ' repeat for all windows
    If hwndTask <> hWnd And IsTask(hwndTask) Then
      intLen = GetWindowTextLength(hwndTask) + 1 ' Get length
      strTitle = Space(intLen) ' Get caption
      intLen = GetWindowText(hwndTask, strTitle, intLen)
      If intLen > 0 Then ' If we have anything, add it
        TaskList(cnt).TaskName = strTitle
        TaskList(cnt).TaskID = hwndTask
        cnt = cnt + 1
      End If
    End If
    hwndTask = GetWindow(hwndTask, GW_HWNDNEXT)
  Loop
  NumTasks = cnt
End Sub

' Give focus to another Task
Public Sub SwitchTo(hWnd As Long)
  Dim ret As Long
  Dim WStyle As Long ' Window Style bits

' Get style bits for window
  WStyle = GetWindowLong(hWnd, GWL_STYLE)
  ' If minimized do a restore
  If WStyle And WS_MINIMIZE Then
    ret = ShowWindow(hWnd, SW_RESTORE)
  End If
  ' Move window to top of z-order/activate; no move/resize
  ret = SetWindowPos(hWnd, HWND_TOP, 0, 0, 0, 0, SWP_NOMOVE Or SWP_NOSIZE Or SWP_SHOWWINDOW)
End Sub

Usage

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'Make a form with 3 Command buttons: cmdExit, cmdRefresh and cmdSwitch. Add a ListBox named lstApp.
'Place the following code in Form1 code window:
Option Explicit

Sub cmdExit_Click()
  Unload Me
End Sub

Sub cmdRefresh_Click()
  Dim i As Integer

  ' Clear the ListBox
  lstApp.Clear
  ' Fills the Task List Structure
  FillTaskList Me.hWnd
  ' Add items into the ListBox
  For i = 0 To NumTasks - 1
    lstApp.AddItem TaskList(i).TaskName
    lstApp.ItemData(lstApp.NewIndex) = TaskList(i).TaskID
  Next
End Sub

Sub cmdSwitch_Click()
  Dim hWnd As Long

  If lstApp.ListIndex < 0 Then Beep: Exit Sub
  ' Get window handle from listbox array
  hWnd = lstApp.ItemData(lstApp.ListIndex)
  ' Switch to the selected Task
  SwitchTo hWnd
End Sub

Sub Form_Load()
  cmdRefresh.Value = True
End Sub

Sub lstApp_DblClick()
  cmdSwitch.Value = True
End Sub