CreateThread function

Hi,

Does anyone know how to use the CreateThread() API
in VB.
I'm trying to use it in my prog. to perform two simultaneous tasks, but it is resulting in a lot
of access violations.

Can anyone help me?

Thanks in advance.
The Beret.

place the below codings in to a class module and impliment your application using that..
'API Declarations
'Creates a new thread
Private Declare Function CreateThread Lib "kernel32" (ByVal lpThreadAttributes As Any, ByVal dwStackSize As Long, ByVal lpStartAddress As Long, lpParameter As Any, ByVal dwCreationFlags As Long, lpThreadID As Long) As Long
'Terminates a thread
Private Declare Function TerminateThread Lib "kernel32" (ByVal hThread As Long, ByVal dwExitCode As Long) As Long
'Sets the priority of a thread
Private Declare Function SetThreadPriority Lib "kernel32" (ByVal hThread As Long, ByVal nPriority As Long) As Long
'Returns the proirity of a thread
Private Declare Function GetThreadPriority Lib "kernel32" (ByVal hThread As Long) As Long
'Enables a disabled Thread
Private Declare Function ResumeThread Lib "kernel32" (ByVal hThread As Long) As Long
'Disables a thread
Private Declare Function SuspendThread Lib "kernel32" (ByVal hThread As Long) As Long
'Returns the handle of the current thread
Private Declare Function GetCurrentThread Lib "kernel32" () As Long
'Returns the ID of the current thread
Private Declare Function GetCurrentThreadId Lib "kernel32" () As Long

'Consts
Private Const MAXLONG = &H7FFFFFFF

'Thread priority consts
Private Const THREAD_BASE_PRIORITY_IDLE = -15
Private Const THREAD_BASE_PRIORITY_LOWRT = 15
Private Const THREAD_BASE_PRIORITY_MAX = 2
Private Const THREAD_BASE_PRIORITY_MIN = -2
Private Const THREAD_PRIORITY_HIGHEST = THREAD_BASE_PRIORITY_MAX
Private Const THREAD_PRIORITY_LOWEST = THREAD_BASE_PRIORITY_MIN
Private Const THREAD_PRIORITY_ABOVE_NORMAL = (THREAD_PRIORITY_HIGHEST - 1)
Private Const THREAD_PRIORITY_BELOW_NORMAL = (THREAD_PRIORITY_LOWEST + 1)
Private Const THREAD_PRIORITY_ERROR_RETURN = (MAXLONG)
Private Const THREAD_PRIORITY_IDLE = THREAD_BASE_PRIORITY_IDLE
Private Const THREAD_PRIORITY_NORMAL = 0
Private Const THREAD_PRIORITY_TIME_CRITICAL = THREAD_BASE_PRIORITY_LOWRT

'Thread creation flags
Private Const CREATE_ALWAYS = 2
Private Const CREATE_NEW = 1
Private Const CREATE_NEW_CONSOLE = &H10
Private Const CREATE_NEW_PROCESS_GROUP = &H200
Private Const CREATE_NO_WINDOW = &H8000000
Private Const CREATE_PROCESS_DEBUG_EVENT = 3
Private Const CREATE_SUSPENDED = &H4
Private Const CREATE_THREAD_DEBUG_EVENT = 2

'Types and Enums
Public Enum ThreadPriority
tpLowest = THREAD_PRIORITY_LOWEST
tpBelowNormal = THREAD_PRIORITY_BELOW_NORMAL
tpNormal = THREAD_PRIORITY_NORMAL
tpAboveNormal = THREAD_PRIORITY_ABOVE_NORMAL
tpHighest = THREAD_PRIORITY_HIGHEST
End Enum

'Vars
Private mThreadHandle As Long
Private mThreadID As Long
Private mPriority As Long
Private mEnabled As Boolean
Private mCreated As Boolean

Public Function CreateNewThread(ByVal cFunction As Long, Optional ByVal cPriority As Long = tpNormal, Optional ByVal cEnabled As Boolean = True)
'Creates a new Thread
Dim mHandle As Long
Dim CreationFlags As Long
Dim lpThreadID As Long

'Look if the thread has already been created
If mCreated = True Then Exit Function

'Look if the thread should be enabled
If cEnabled = True Then
CreationFlags = 0
Else
'Create a disabled thread, can be enabled later with the
''Enabled' property
CreationFlags = CREATE_SUSPENDED
End If

'The CreateThread Function returns the handle of the created thread;
'if the handle is 0, it failed creating the thread
mHandle = CreateThread(ByVal 0&, ByVal 0&, cFunction, ByVal 0&, CreationFlags, lpThreadID)

If mHandle = 0 Then 'Failed creating the thread
'Insert your own error handling
'Debug.Print "InitializeThread Function in clsThreading failed creating a new thread"
Else
mThreadHandle = mHandle
mThreadID = lpThreadID
mCreated = True
End If
End Function

Public Function TerminateCurrentThread()
'Terminates the current thread

'Ignore errors to prevent crashing if no thread has been created
On Error Resume Next
'Terminate the thread to prevent crashing if the app is closed
'and the thread is still running (dangerous!)
Call TerminateThread(mThreadHandle, ByVal 0&)
mCreated = False
End Function

Public Property Get ThreadHandle() As Long
'Returns the Handle of the current Thread
ThreadHandle = mThreadHandle
End Property

Public Property Get ThreadID() As Long
'Returns the ID of the current thread
ThreadID = mThreadID
End Property

Public Property Get Priority() As Long
'Returns a long value because the thread might have other priorities
'than our five in the enum

'Ignore errors to prevent crashing if no thread has been created
On Error Resume Next
Priority = GetThreadPriority(mThreadHandle)
End Property

Public Property Let Priority(ByVal tmpValue As Long)
'Sets the Thread Priority of the actual thread
mPriority = tmpValue
Call SetThreadPriority(mThreadHandle, tmpValue)
End Property

Public Property Get Enabled() As Boolean
'Returns whether the Thread is enabled or not
Enabled = mEnabled
End Property

Public Property Let Enabled(ByVal tmpValue As Boolean)
'Enables/Disables the Thread

'Ignore errors to prevent crashing if no thread has been created
On Error Resume Next
If tmpValue = True Then
'Enable the thread
Call ResumeThread(mThreadHandle)
ElseIf tmpValue = False Then
'Disable the thread
Call SuspendThread(mThreadHandle)
End If
End Property

Private Sub Class_Terminate()
'Terminate the thread to prevent crashing if the app is closed
'and the thread is still running (dangerous!)
Call TerminateCurrentThread
End Sub

This comes from Api-guide, a free tool you can download from
http://www.allapi.net/

'In a form
'Add a command button to the form
private Sub Command1_Click()
'KPD-Team 1999
'URL: http://www.allapi.net/
'E-Mail: [email protected]
'After you click this button, try to move the window
'You will see that the AsyncThread-function was executed asynchronously
hThread = CreateThread(byval 0&, byval 0&, AddressOf AsyncThread, byval 0&, byval 0&, hThreadID)
CloseHandle hThread
End Sub
private Sub Form_Unload(Cancel as Integer)
'If the thread is still running, close it
If hThread <> 0 then TerminateThread hThread, 0
End Sub
'In a module
Declare Sub Sleep Lib "kernel32" (byval dwMilliseconds as Long)
Declare Function CreateThread Lib "kernel32" (lpThreadAttributes as Any, byval dwStackSize as Long, byval lpStartAddress as Long, lpParameter as Any, byval dwCreationFlags as Long, lpThreadID as Long) as Long
Declare Function TerminateThread Lib "kernel32" (byval hThread as Long, byval dwExitCode as Long) as Long
Declare Function CloseHandle Lib "kernel32" (byval hObject as Long) as Long
public hThread as Long, hThreadID as Long
public Sub AsyncThread()
'let this thread sleep for 10 seconds
Sleep 10000
hThread = 0
End Sub




Special thanks to Lothar "the Great" Haensler, Tom Archer, Chris Eastwood, TCartwright, Bruno Paris, Dr_Michael
and all the other wonderful people who made and make Codeguru a great place.
Come back soon, you Gurus.

The Rater