DOCUMENT:Q102829  07-MAY-2001  [visualc]
TITLE   :How to Replace a View in a CMDIChildWnd Window
PRODUCT :Microsoft C Compiler
PROD/VER::1.0,1.51,1.52,2.0,2.1,l.5
OPER/SYS:
KEYWORDS:kbfile kbDocView kbMFC kbVC100 kbVC150 kbVC200 kbVC210 kbArchitecture

======================================================================
-------------------------------------------------------------------------------
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 
-------------------------------------------------------------------------------

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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Copyright Microsoft Corporation 2001.