How to Replace a View in a CMDIChildWnd Window

ID: Q102829

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

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
Version : winnt:1.0,2.0,2.1
Platform : winnt
Issue type :