Q102829: How to Replace a View in a CMDIChildWnd Window

Article: Q102829
Product(s): Microsoft C Compiler
Version(s): 1.0,1.51,1.52,2.0,2.1,l.5
Operating System(s): 
Keyword(s): kbfile kbDocView kbMFC kbVC100 kbVC150 kbVC200 kbVC210 kbArchitecture
Last Modified: 07-MAY-2001

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++ for Windows, 16-bit edition, versions 1.0, l.5, 1.51, 1.52 
   - Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1 
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There is an equivalent VC4.0 (32-bit) sample available under the name of
VWRPLC32.

SUMMARY
=======

The VWRPLC sample demonstrates how a programmer might write a ReplaceView()
member function for a CMDIChildWnd-derived class.

Download VWRPLC.EXE, a self-extracting file, from the Microsoft Software Library
(MSL) on the following services:

The following file is available for download from the Microsoft Software
Library:

  Vwrplc.exe
  (http://support.microsoft.com/download/support/mslfiles/Vwrplc.exe)

For more information about downloading files from the Microsoft Software Library,
please see the following article in the Microsoft Knowledge Base:

  Q119591 How to Obtain Microsoft Support Files from Online Services


NOTE: Use the -d option when running VWRPLC.EXE to decompress the file and
re-create the proper directory structure.

MORE INFORMATION
================

The core of the sample can be found in FRAME.CPP. You will see the following
function:

     BOOL CFrame::ReplaceView(CRuntimeClass * pViewClass)
     {
      CCreateContext context;
      CView * pCurrentView;

      // If no active view for the frame, return FALSE because this
      // function retrieves the current document from the active view.
      if ((pCurrentView=GetActiveView())==NULL)
         return FALSE;

      // If you're already displaying this kind of view, no need to go
      // further.
      if ((pCurrentView->IsKindOf(pViewClass))==TRUE)
         return TRUE;

       // Get pointer to CDocument object so that it can be used in the
       // creation process of the new view.
       CDocument * pDoc= pCurrentView->GetDocument();

        // Set flag so that document will not be deleted when view is
        // destroyed.
        BOOL bAutoDelete=pDoc->m_bAutoDelete;
         pDoc->m_bAutoDelete=FALSE;
        // Delete existing view
        pCurrentView->DestroyWindow();
        // restore flag
        pDoc->m_bAutoDelete=bAutoDelete;

       // Create new view and redraw.
       context.m_pNewViewClass=pViewClass;
       context.m_pCurrentDoc=pDoc;
       context.m_pNewDocTemplate=NULL;
       context.m_pLastView=NULL;
       context.m_pCurrentFrame=this;

       CView * pNewView = (CView *) pViewClass->CreateObject();

       if (pNewView == NULL)
         {
         TRACE1("Warning: Dynamic create of view type %Fs failed\n",
                        pViewClass->m_lpszClassName);
              return FALSE;
         }

        if (!pNewView->Create(NULL, NULL, AFX_WS_DEFAULT_VIEW,
              CRect(0,0,0,0), this, AFX_IDW_PANE_FIRST, &context))
              {
              TRACE0("Warning: couldn't create view for frame\n");
                 return FALSE; // Programmer can assume FALSE return value
                              // from this function means that there
                              // isn't a view.
              }

       // WM_INITIALUPDATE is define in AFXPRIV.H.
       pNewView->SendMessage(WM_INITIALUPDATE, 0, 0);

       RecalcLayout();

       pNewView->UpdateWindow();

       SetActiveView(pNewView);

       return TRUE;
     }

The function receives a pointer to CRuntimeClass object for the new view that is
desired. It destroys the old view and replaces it with a new view of the same
CDocument. When DestroyWindow() is called for the old view, this causes a
"delete this" in the CView::PostNcDestroy() function. Also, the CView::~CView
destructor calls CView::RemoveView(), which removes the view from the document's
view list.

REFERENCES
==========

For more information, please see the following article in the Microsoft
Knowledge Base:

  Q141499 SAMPLE: VWRPLC32, Replacing a View in a CMDIChildWnd Window

Additional query words:

======================================================================
Keywords          : kbfile kbDocView kbMFC kbVC100 kbVC150 kbVC200 kbVC210 kbArchitecture 
Technology        : kbAudDeveloper kbMFC
Version           : :1.0,1.51,1.52,2.0,2.1,l.5

=============================================================================

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