SAMPLE: VSWAP Demos Multiple-View Switching in SDI

ID: Q141333

The information in this article applies to:

SUMMARY

VSWAP demonstrates methods of switching between multiple views on a single document in a single-document interface (SDI) application. VSWAP displays two form views and a normal view that displays the list of data collected in the two form views.

NOTE: This is the 16-bit version of this sample. There is an equivalent 32-bit sample available under the name VSWAP32.

This sample application demonstrates using DDX/DDV (dialog data exchange/dialog data validation), with correct document updating and data validation when switching between views. It also correctly catches unsaved/unvalidated data when the application is closed.

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

Vswap.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
After downloading the file, use the following command to extract the sample and build the appropriate directory structure: 

   VSWAP.EXE -d


MORE INFORMATION

The most important implementations of this are in: 


   CVswapApp::InitInstance
   CVswapApp::SwitchView
   CVswapApp::SaveActiveViewsData
The standard InitInstance code creates an initial frame, document, and view during the call to OnFileNew. The code added to the end of the InitInstance in this sample creates the view objects for the extra views used in this application and stores their pointers in a CVswapApp member array. It then cycles through a loop which creates the windows for the view objects. Each view window is created with a unique child window ID and a CCreateContext object that associates each view with the same CDocument object, which was created by OnFileNew. Finally, the sample code triggers the OnInitialUpdate for the extra views.

The SwitchView function created in this sample swaps the current view with a previously hidden view. It accomplishes this by first switching their child window IDs. This is necessary because MFC relies on the standard view pane having the child window ID of AFX_IDW_PANE_FIRST. The rest of the code hides the current view and tells MFC to repaint and begin using the new view.

The SaveActiveViewsData is used to save the information from the active view to the document object. It is called by SwitchView whenever a view is switched. SaveActiveViewsData subsequently calls the view's SetToDoc, which actually updates the data from the form view to the document by calling UpdateData with an argument of TRUE. This function uses the DDX/DDV functions specified in the view's DoDataExchange.

Sample Code


   The SwitchView function is included here as a reference.

   CView* CVswapApp::SwitchView( UINT nIndex )
   {
       ASSERT( nIndex >=0 && nIndex < NUMVIEWS );

       CView* pNewView = m_pViews[nIndex];

       CView* pActiveView =
       ((CFrameWnd*) m_pMainWnd)->GetActiveView();

       if ( !pActiveView )    // No currently active view
           return NULL;

       if ( pNewView == pActiveView )    // Already there
           return pActiveView;

       // Update Doc's data if needed
       // Don't change view if data valiation fails
       if ( ! SaveActiveViewsData() )
       {
           return pActiveView;
       }

       m_nCurView = nIndex;    // Store the new current view's index

       // exchange view window IDs so RecalcLayout() works
       UINT temp = ::GetWindowWord(pActiveView->m_hWnd, GWW_ID);
       ::SetWindowWord(pActiveView->m_hWnd, GWW_ID,
             ::GetWindowWord(pNewView->m_hWnd, GWW_ID));
       ::SetWindowWord(pNewView->m_hWnd, GWW_ID, temp);

       // Display and update the new current view - hide the old one
       pActiveView->ShowWindow(SW_HIDE);
       pNewView->ShowWindow(SW_SHOW);
       ((CFrameWnd*) m_pMainWnd)->SetActiveView(pNewView);
       ((CFrameWnd*) m_pMainWnd)->RecalcLayout();
       pNewView->Invalidate();
       return pActiveView;
   }


REFERENCES

For examples of other applications that switch views, please refer to the following SAMPLES: 


   COLLECT (SDI)
   ENROLL  (SDI)
   VWRPLC  (MDI)
   SPLIT   (Splitter).
For more information on DDX and DDV routines, please see Technical Note 26: DDX and DDV Routines in the Microsoft Development Library.

For additional information, please see the following article(s) in the Microsoft Knowledge Base:
Q99562 Switching Views in a Single Document Interface Program

Additional query words: VSWAP VSWAP32 


Keywords          : kbcode kbsample kbDocView kbMFC kbVC 
Version           : 1.0 1.5 1.51 1.52 2.0 2.1 2.52
Platform          : WINDOWS 
Issue type        :

Last Reviewed: August 8, 1999