Re: Using threads in a dialog based MFC app in C++
Jeffro wrote:
I'm trying to learn threads so I started a C++ MFC app in Visual Studio
2008. It's a single dialog based app with an Edit control, a Run button
and an Exit button. The Run button sends updates to the edit control in
a continual loop. How do I get the program to respond to events? That
is, to close when I press the Exit button? Do I even need a thread in
this situation? Even if threads aren't necessary, please show me how it
would be done (with threads).
If you want to learn about threads Joe's site is highly recommended.
But you don't have to use a thread. You can use the printing loop
method. Add this:
// ................................................................
bool bGlbAbort= false;
//Returns non zerro if continue.
BOOL CALLBACK _RAAbortProc( HDC, int )
{
MSG msg;
while( ::PeekMessage( &msg, NULL, NULL, NULL, PM_NOREMOVE ) )
{
if( ! AfxPumpMessage( ) )
return FALSE;
}
return ! bGlbAbort;
}
What ever button needs to stop the loop should set a flag so that
GetIsCancel( ) returns true. I have never tried this beyond a progress
dialog with a cancel button, but I don't see why it won't work with an
app dialog. I use it while building a report object then hand it to the
dc for the printing loop. So the bGlbAbort is not necessary.
Your buttons are dead because you are blocking the message pump. So,
somewhere in your blocking code:
void CThreadPracticeDlg::OnBnClickedRun()
{
int i = 0;
while (1) {
if (i >= 10) {
i = 0;
}
if( GetIsCancel( ) )
//Post quit, return, whatever....
char intString[2];
_itoa(i,intString,10);
CString msg = CString(intString);
m_edit1.SetWindowTextW(msg);
i++;
//Not sure that this will mess catching the button press
//If you are going to be gone for extended times you may
//be better off with a second thread.
Sleep(500);
}
}
void CThreadPracticeDlg::OnBnClickedExit()
{
exit(0);
}
Also, you don't need itoa and the char array.
CString strT;
strT.Format( _T("%d"), i );
Once you have used threads a few times they are not that bad. Worker
threads are very easy to use. But you will need to post a message to the
GUI thread and use a semaphore to share the data rather than alter the
window directly.
See Joe's site:
http://www.flounder.com/mvp_tips.htm
Best, Dan.