VB Forum / Win API / September 2003

Here is some sample code in which the
waitformultipleobjects does continuous notifications. I
created the example as a standard module.

Option Explicit

Public Const WAIT_FAILED = &HFFFF
Public Const FILE_NOTIFY_CHANGE_ALL = &H4 Or &H2 Or &H1
Or &H8 Or &H10 Or &H100
Public Const INFINITE = &HFFFF
Public Const WAIT_OBJECT_0 = &H0
Public Declare Function FindFirstChangeNotification
Lib "kernel32" Alias "FindFirstChangeNotificationA"
(ByVal lpPathName As String, ByVal bWatchSubtree As Long,
ByVal dwNotifyFilter As Long) As Long
Public Declare Function FindNextChangeNotification
Lib "kernel32" (ByVal hChangeHandle As Long) As Long
Public Declare Function WaitForSingleObject
Lib "kernel32" (ByVal hHandle As Long, ByVal
dwMilliseconds As Long) As Long
Public Declare Function WaitForMultipleObjects
Lib "kernel32" ( _
   ByVal nCount As Long, lpHandles As Long, ByVal
bWaitAll _
   As Long, ByVal dwMilliseconds As Long) As Long

Sub Main()

 Dim strTgtDir1 As String, strTgtDir2 As String,
varRtnCode, lngNumNotifyDirs As Long
 Dim lngNotificationHandle(), lngDirToProcess As Long
 
 strTgtDir1 = "C:\Documents and Settings\All
Users\Documents\My Pictures"
 strTgtDir2 = "C:\Documents and Settings\All
Users\Documents\My Music"

 'Setup initial notifications
 lngNumNotifyDirs = 0
 ReDim Preserve lngNotificationHandle(lngNumNotifyDirs +
1)
 lngNotificationHandle(0) = FindFirstChangeNotification
(strTgtDir1, True, FILE_NOTIFY_CHANGE_ALL)
 lngNumNotifyDirs = lngNumNotifyDirs + 1
 ReDim Preserve lngNotificationHandle(lngNumNotifyDirs +
1)
 lngNotificationHandle(1) = FindFirstChangeNotification
(strTgtDir2, True, FILE_NOTIFY_CHANGE_ALL)
 
 'When one of the objects becomes signalled the wait
function
 'returns with the index of the array element that
changed.
 '
RestartScan:
 Do
   lngDirToProcess = WaitForMultipleObjects
(lngNumNotifyDirs, lngNotificationHandle(1), False,
INFINITE)
   If varRtnCode = WAIT_FAILED Then GoTo Finished
   lngDirToProcess = lngDirToProcess - WAIT_OBJECT_0
   If lngDirToProcess >= 0 Then
     'Go process the directory
     Exit Do
   End If
   'Pause before looping again
   varRtnCode = WaitForSingleObject(lngNotificationHandle
(1), 500&)
   DoEvents
   DoEvents
   DoEvents
 Loop

 'Copy files to a backup drive
 'Call sf_DirProcessFiles(strSearchSpec, strScanCmd,
colFileNames)

 'Start notification check for next time around
 varRtnCode = FindNextChangeNotification
(lngNotificationHandle(lngDirToProcess))
 GoTo RestartScan

Finished:

End Sub