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Thread with base class CFormView

Posted on 1998-09-22
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Last Modified: 2013-11-19
How do I create a user-interface thread which has a base class of CFormView (instead of CWnd)?
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Question by:p1
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8 Comments
 
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Expert Comment

by:Norbert
ID: 1322461
User Interface Thread base class is CWinThread it is never a CWnd or CWnd derived Class
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Author Comment

by:p1
ID: 1322462
My question is to implement a project which is MDI based format and
it will contain two different views. We want one thread to be setup for
each view.

Thus we want to use user interface thread because we need to
'postmessage' between the two windows.

Can you list  the procedure needed to do this?
Or can you give me any example/source code?
Thanks

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LVL 3

Expert Comment

by:plaroche
ID: 1322463
"Thus we want to use user interface thread because we need to
 'postmessage' between the two windows. "

What would that really change?  Simple threads can still post messages to other windows.

Could you clarify what the threads would be doing? Maybe a user-interface thread is too much for your use.

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Author Comment

by:p1
ID: 1322464
Let me rephrase my original question again.
How do I create a USER-INTERFACE THREAD WINDOW which has a base class of CFormView (instead of CWnd). That is we like the user-interface thread to have its own window which is of base class CFormView.

I have difficulties in constructing it , and is asking for advices on how to do it.
Becasue I don't know how to combine the multithreading architecture and the CFormView construction code together - all I can do is to create a user-interface thread which has its own window of base class CWnd.

Once again, thank you for your time.

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Accepted Solution

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Norbert earned 100 total points
ID: 1322465
Answer is coming
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LVL 3

Expert Comment

by:Norbert
ID: 1322466
Generate a Class derived from CWinThread
Look into online help to see what you need building an CWinThread derived class
Start the Thread using
            AfxBeginThread(RUNTIME_CLASS(CYourWinThreadDerivedClass));
// have a look into online help for the parameters of AfxBeginThread
Now your Thread is running and AfxBeginThread or one of the functions that are called during the thread initialisation will call
InitInstance of the generated CYourWinThreadDerivedClass Object.
Inside the InitInstance function create a Frame window
and asign it to m_pMainWnd member variable of your CYourWinThreadDerivedClass Object  and create the View:
BOOL CYourWinThreadDerivedClass ::InitInstance()
{
  CCreateContext Context;
  CMenu MyMenu;
  CMainFrame* MyFrame=new CMainFrame;
  m_pMainWnd=MyFrame;
  if (!MyFrame->Create(NULL, _T("Title Of your Window")))
    return FALSE;
  MyMenu.LoadMenu(IDR_MAINFRAME);
  if(MyFrame->GetMenu())            MyFrame->GetMenu()->DestroyMenu();
  MyFrame->SetMenu(&MyMenu);
  MyMenu.Detach();
  Context.m_pNewViewClass=RUNTIME_CLASS(CYourView);
  CYourView* MyView=
         (CYourView*)MyFrame->CreateView(&Context);
   MyFrame->SetActiveView(MyView,TRUE);
  MyView->ShowWindow(SW_SHOW);
  ActivateFrame();
  RecalcLayout(TRUE);

  return true;
}

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Author Comment

by:p1
ID: 1322467
Dear Norbert,

Sorry for replying late!!!
I have tried the method suggested by you but I found that the frame cannot be created.
I think this may due to the problem of the variable m_pMainWnd...each time
I execute my program, error occurs.

I used the debugger to locat the error, the error occurs at:

if (pParentWnd == NULL)
{
    CWnd* pMainWnd = AfxGetThread()->m_pMainWnd;
    ASSERT(pMainWnd != NULL);
    ASSERT_KINDOF(CMDIFrameWnd, pMainWnd);  // error occurs at here
    pParentWnd = (CMDIFrameWnd*)pMainWnd;
}

How can I correct this error?
Thanks
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LVL 3

Expert Comment

by:Norbert
ID: 1322468
if I found the right location the assertion happens inside the CMDIChildWnd::Create(...) function so I will ask some questions:

1.From wich thread do you call the Create function ?
AfxGetThread returns a pointer to the actual running thread. So if you call the Create function from outside the thread you get the wrong pointer.

2.Peece of my suggested code:
CMainFrame* MyFrame=new CMainFrame;
  m_pMainWnd=MyFrame;
  if (!MyFrame->Create(NULL, _T("Title Of your Window")))
    return FALSE;
Is CMainFrame derived from CMDIFrameWnd

If you only want to create a child window of a CMDIFrameWnd inside the thread may be the following will work. But I am absolutely not sure about it because you are crossing threads and I do not know how thread safe the MFC is:
BOOL CYourWinThreadDerivedClass ::InitInstance()
{
  CCreateContext Context;
  CMenu MyMenu;
  CYourMDIChildClass* MyFrame=new CYourMDIChildClass;
  m_pMainWnd=AfxGetApp()->m_pMainWnd;
  if (!MyFrame->Create(NULL, _T("Title Of your Window")))
    return FALSE;
.
rest of InitInstance
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