C / C++ / MFC

18-Feb-03 16:42

let say i had created a thread by

hThread = CreateThread(
NULL, // default security attributes
0, // use default stack size
ThreadFunc, // thread function
&lpVoid // argument to thread function
0, // use default creation flags
&dwThreadId); // returns the thread identifier

with thread function

unsigned long __stdcall CProjectv1Dlg::ThreadFunc(void* lpVoid)
{//let say again
while(1){
if(int a == 1)
m_result += " success";
}
return 0;
}

i oso created an editbox with a Cstring variable m_result.

now, my question is how can i update the editbox through the m_result variable?

thks for all the advice and help Smile | :)

regards,

afender

Chintan18-Feb-03 18:30

18-Feb-03 18:30

You can pass dialog class's address as the parameter of the thread function and then through that pointer you can access variables and functions of your dialog class.

C.R.Naik

Chintan18-Feb-03 18:34

18-Feb-03 18:34

You can do it by passing dialog class's address as the parameter to the thread function and then access dialog class's variable through that pointer.

C.R.Naik

Anonymous18-Feb-03 19:33

Anonymous

18-Feb-03 19:33

how can i pass the dialog class's address..as in how should i write on the third argument of the createThread()

sorry to trouble again

Regards

afender

Hans Ruck19-Feb-03 3:54

Hans Ruck

19-Feb-03 3:54

Anonymous wrote:
on the third argument of the createThread()

If you're using MFC inside of the worker thread then call AfxBeginThread to start it. It's the only way you can make MFC objects to acquire correctly the TLS data they use.

rechi

Chintan19-Feb-03 22:10

19-Feb-03 22:10

Simply by putting second parameter of AfxBeginThread as "this". For further process...please refere following replies for this question.

C.R.Naik

afender18-Feb-03 19:55

18-Feb-03 19:55

hi
below are the code i had modified

unsigned long __stdcall CProjectv1Dlg::ThreadFunc(void* lpvoid)
{
CProjectv1Dlg *myThis = (CProjectv1Dlg *)lpvoid;
while(1){
if( a == 0){
myThis->myThis = "read success";
myThis->UpdateData(FALSE);

}
}

}
now my problem lies on the myThis->UpdateData(FALSE), it seems i cannot directly use this function. Any other way to update the data?

thks again

afender

Chintan19-Feb-03 22:00

19-Feb-03 22:00

I supposed that ID of your dialog's Edit Box is IDC_EDIT_MYTHIS, then your problem can be solved by the following code :

unsigned long __stdcall CProjectv1Dlg::ThreadFunc(void* lpvoid)
{
CProjectv1Dlg *myThis = (CProjectv1Dlg *)lpvoid;
while(1){
if( a == 0){
//myThis->myThis = "read success";
//myThis->UpdateData(FALSE);
::SetWindowText(::GetDlgItem(myThis->m_hWnd, IDC_EDIT_MYTHIS), "read success");
}
}

}

Welcome

C.R.Naik

afender18-Feb-03 19:57

18-Feb-03 19:57

hi
below are the code i had modified

unsigned long __stdcall CProjectv1Dlg::ThreadFunc(void* lpvoid)
{
CProjectv1Dlg *myThis = (CProjectv1Dlg *)lpvoid;
while(1){
if( a == 0){
myThis->m_result = "read success";
myThis->UpdateData(FALSE);

}
}

}
now my problem lies on the myThis->UpdateData(FALSE), it seems i cannot directly use this function. Any other way to update the data?

thks again

afender

HENDRIK R18-Feb-03 22:04

HENDRIK R

18-Feb-03 22:04

The problem should be that UpdateData is protected and can not be accessed from without the class. Thus you could add a public function to your dialog which calls UpdateData and changes the value of your member variable.

afender9919-Feb-03 4:08

afender99

19-Feb-03 4:08

unsigned long __stdcall CProjectv1Dlg::ThreadFunc(void* lpvoid) <br />
{<br />
CProjectv1Dlg *myThis = (CProjectv1Dlg *)lpvoid;<br />
while(1){<br />
if( a == 0){<br />
myThis->display(); <br />
           }<br />
        }<br />
}<br />
<br />
void CProjectv1Dlg::display()<br />
{<br />
UpdateData(FALSE);<br />
}

is this what u means?

regards

afender

Joe Woodbury19-Feb-03 9:50

Joe Woodbury

19-Feb-03 9:50

(This post has been edited to correct a stupid mistake on my part. See later follow-up for more information.)

Never update a window directly from a worker thread. You should also avoid using SendMessage from a worker thread to a window. Instead, use PostMessage and use a user defined message (WM_USER + x.)

In your example, you'll either need to pass a discrete value, which the dialog will then use to obtain the string itself and pass that as one of the parameters of the user message. Or put a critical section around any reading/writing of m_result.

afender19-Feb-03 15:41

19-Feb-03 15:41

i still not quite understand on how to do it.

ok, let say i put the PostThreadMessage() in the worker thread as follow

unsigned long __stdcall CProjectv1Dlg::ThreadFunc(void* lpVoid)
{
CProjectv1Dlg *myThis = (CProjectv1Dlg *)lpVoid;
while(1){
if(count == 0){
m_result += "success";
PostThreadMessage(myThis->TID, WM_USER + 0x10, 0, 0);
}
}
return 0;
}

where i use the

TID = GetCurrentThreadId();

so now the question is,

let say i want to update the edit box, how to determine the WM_USER + x? or just simply put a value in the specific range.

regards

afender

Joe Woodbury19-Feb-03 19:37

Joe Woodbury

19-Feb-03 19:37

Unfortunately, I mixed two solutions together and blundered. You shouldn't use PostThreadMessage, but rather call the PostMessage of the dialog from the thread. (i.e. mythis->PostMessage(WM_USER + 0x10....)

The value for your user message can be anything, just make sure it's unique (I've made that mistake before.)

You then need to make a custom handler for the Dialog for that specific user message. To make the dialog flexible, in the past I've passed and IDS_ define as the WPARAM (or LPARAM) and then the message handler simply loads that string and updates the edit control. (If you know that only the thread will be setting m_result, then you can get away without a critical section, but that may come back to haunt you someday.)

Here's a link to help explain that.

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclib/html/_MFCNOTES_TN006.asp[^]

afender20-Feb-03 2:41