Wait...WAIT! Suppose your VB app has to wait

The tip involves making a VB app wait for the completion of some other process outside VB.

Wait...WAIT! Suppose Your VB App Has to Wait

SearchVB reader Derek E. Brown sends in this tip that should be very useful in a number of situations that can arise. The tip involves making a VB app wait for the completion of some other process outside VB. While Derek has a specific purpose in mind for this one, it should be fairly easy to modify for a number of different situations.

I found this to be an extremely useful piece of code for running an application from within VB and having the VB app wait until the outside process is complete. I have a program that has to wait until an uploaded zip file is unzipped before continued processing can take place. The code below involves a few API's, and though it's rather long and involved, I have yet to get an error using it.

'**************************************
'Windows API/Global Declarations for :Un
'zipper
'**************************************
Private Const ZIPSIG = &H4034B50
Private Const ziputil = "c:Program FilesPKUnzipPkzip25.exe"
Private Const SYNCHRONIZE = &H100000
Private Const INFINITE = &HFFFFFFFF
'API's to monitor the status of Pkzip

Private Declare Function OpenProcess Lib "kernel32" (ByVal DesiredAccess As
Long, _ ByVal bInheritHandle As Long, ByVal ProcessId As Long) As Long
Private Declare Function WaitForSingleObject Lib "kernel32" (ByVal hHandle
As Long, _ ByVal Milliseconds As Long) As Long Private Declare Function
CloseHandle Lib "kernel32"
(ByVal hObject As Long) As Long Private Type ZFHeader Signature As Long End Type

***********************************
Function fn_UnZipQReportFile() As Boolean
Dim FileToUnzip As String
Dim int_FilNum As Integer
Dim zhdr As ZFHeader
On Error Goto ErrorHandler:
fn_UnZipQReportFile = False
int_FilNum = 1

FileToUnzip = "C:Test.zip"

If FSO.FileExists(FileToUnzip) Then
Open FileToUnzip For Binary Access Read As #int_FilNum
Get #int_FilNum, , zhdr
If zhdr.Signature = ZIPSIG Then
If Array(int_ArrayCount).Password = "" Then
Err.Description = "No password supplied. File will Not unzip
If password protected. & _ Check database For empty (null) report password."
Goto ErrorHandler Else CmdLine = ziputil & " -ext -pass=" &
Array(int_ArrayCount).Password & " -dir=full -over=all " & FileToUnzip &
" " & Array(int_ArrayCount).Path
End If RetVal = Shell(CmdLine, vbMinimizedNoFocus)
If RetVal <> 0 Then sb_WaitForTemination (RetVal)
fn_UnZipQReportFile = True Else
Err.Description = "Zip file doesn't exist, " & FileToUnzip &
" " Goto ErrorHandler End If Else
Err.Description = "Zip file is empty, " & FileToUnzip & " "
Goto ErrorHandler End If
End If Exit Function
ErrorHandler: Call sub_Error_Log 'A seperate sub to write to an error log.
Resume Next
End Function
*************************************************
Private Sub sb_WaitForTemination(RetVl As Integer)
On Error Goto ErrorHandler:
Dim phnd&
phnd = OpenProcess(SYNCHRONIZE, 0, RetVl)

If phnd <> 0 Then
Call WaitForSingleObject(phnd, INFINITE)
Call CloseHandle(phnd)
End If
Exit Sub
ErrorHandler:
Err.Source = "sb_WaitForTermination in class Unzip in UnZipper"
Call sub_Error_Log
Resume Next
End Sub

Thanks, Derek. We'll be sending you a SearchVB denim shirt as a thank you for your submission. If you have a different solution for this problem, be sure to let us know. You can send your solution to us at tips@searchvb.com.
This was first published in October 2000

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