Microsoft KB Archive/141333

= VSWAP Demos Multiple-View Switching in SDI =

Article ID: 141333

Article Last Modified on 11/21/2006

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APPLIES TO

 Microsoft Foundation Class Library 4.2, when used with:  Microsoft Visual C++ 1.5 Professional Edition

 Microsoft Visual C++ 1.51

 Microsoft Visual C++ 1.52 Professional Edition 

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This article was previously published under Q141333

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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 files are available for download from the Microsoft Download Center:

Vswap.exe

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.

After downloading the file, use the following command to extract the sample and build the appropriate directory structure: <pre class="fixed_text">  VSWAP.EXE -d

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MORE INFORMATION
The most important implementations of this are in: <pre class="fixed_text">  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; }

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