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CWinThread and CDialog - getting them work together

Posted on 2008-06-25
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Last Modified: 2013-12-14
Hello,

I have created a new thread - that works perfect. Now I want to display a CDialog in this thread. In a Thread Montor a new thread with the name of the dialog is shown but i can not see the dialog. I have called the dialog without a thread - that worked. That have I done wrong?

Below some code which may help.

Greedings Sonja
// Call of the thread
//--------------------
 
  CMyThread * MyThread = new CMyThread();
  MyThread ->CreateThread(CREATE_SUSPENDED);
  MyThread ->m_Parameter = Parameter;
  MyThread ->m_pDialog = pDialog;
  MyThread ->ResumeThread();
 
// MyThread.cpp - class CMyThread : public CWinThread
//--------------
 
int MyThread::Run()
{
  //pDialog initialized to NULL in the constructor of CMyWnd class
   CMyDialog* pDialog = new CMyDialog();
   //Check if new succeeded and we got a valid pointer to a dialog object
   if(pDialog != NULL)
   {
      BOOL ret = pDialog->Create(IDD_MYDIALOG,NULL); // <- In the debugger it stops here
      if(!ret)   //Create failed.
         AfxMessageBox("Error creating Dialog");
      pDialog->ShowWindow(SW_SHOW);
   }
   else
      AfxMessageBox("Error Creating Dialog Object");
  return 0;
}

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Question by:Sonja_M
7 Comments
 
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Expert Comment

by:alb66
ID: 21866855
You should avoid to open a dialog in a different thread
0
 
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Expert Comment

by:AndyAinscow
ID: 21867022
There are two types of thread.  A worker thread (does NOT support windows) and a UI thread (does support windows).
Which type are you using?  I suspect the first.
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Expert Comment

by:mrwad99
ID: 21873986
>> int MyThread::Run()

Don't forget that when Run() returns, the thread ends.  So your thread will only be around for a split second.  

Generally it is a good idea not to override CWinThread::Run().  A better place to put your code is in InitInstance().  Add this function to your class and move the code to create the dialog into it.  This should resolve the problem.

HTH
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LVL 19

Expert Comment

by:mrwad99
ID: 21874527
OK this works.  The key is in setting CWinThread::m_pMainWnd to be your dialog:

BOOL MyThread::InitInstance()
{
	CMyDialog* pDialog = new CMyDialog();
	BOOL ret = pDialog->Create(IDD_MYDIALOG,NULL); 
 
	m_pMainWnd = pDialog;
	
	m_pMainWnd->UpdateWindow();
	m_pMainWnd->ShowWindow( SW_SHOW );
 
	return CWinThread::InitInstance();
}

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Accepted Solution

by:
mrwad99 earned 499 total points
ID: 21874798
>> The key is in setting CWinThread::m_pMainWnd to be your dialog:

Sorry but that is not true, I made a mistake.  The key is in returning TRUE (not CWinThread::InitInstance(), which returns FALSE, thereby shutting down the thread) from InitInstance().  You don't have to do anything with m_pMainWnd.

Revised code follows.
BOOL MyThread::InitInstance()
{
        CMyDialog* pDialog = new CMyDialog();
        BOOL ret = pDialog->Create(IDD_MYDIALOG,NULL); 
        
        pDialog->UpdateWindow();
        pDialog->ShowWindow( SW_SHOW );
 
        return TRUE;
}

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Author Closing Comment

by:Sonja_M
ID: 31470621
Thank you! Now it is working! Problem solved.
0
 
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Expert Comment

by:mrwad99
ID: 21876669
Glad to help.
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