怎样让GetActiveView以及GetActiveDocument的返回值不为NULL？

[yangsaibing]

我的代码是这样的，自己建立一个基类为CMDIChildWnd的类CMyMDIWnd，里面有这样一些代码：
int CMyMDIWnd::SetLstInfo(int nObjFlag)
{
CDataDoc *pDoc = NULL;
CView *pView = NULL;
CDocument *pDocTemp = NULL;
pView = this->GetActiveView();
pDocTemp = this->GetActiveDocument() ;
if(!pDocTemp) return 0;
if(!pDocTemp->IsKindOf(RUNTIME_CLASS(CDataDoc)))
return 0;

pDoc = (CDataDoc*) pDocTemp;
if(pDoc) {
pDoc->SetViewData(nObjFlag);
return 1;

}
return 0;
}
请问，为什么调用时pView以及pDocTemp里的值总是为空呢？怎样让GetActiveView以及GetActiveDocument的返回值不为NULL？

[蒋晟]

如果使用应用程序向导生成的代码，则不会有这种情况。

[yangsaibing]

请问，如何多个激活View中的一个，请高手帮帮我

[蒋晟]

see VWRPLC sample in MSDN

[蒋晟]

VWRPLC32 Replacing a View in a CMDIChildWnd Window
ID: Q141499


--------------------------------------------------------------------------------
The information in this article applies to:

The Microsoft Foundation Classes (MFC), used with:
Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1, 4.2, 5.0, 6.0

--------------------------------------------------------------------------------
This is the 32-bit version of this sample.

SUMMARY
The VWRPLC32 sample demonstrates how, in a Multidocument Interface (MDI) application, a programmer can write a ReplaceView() member function for a CMDIChildWnd-derived class.

NOTE: The following samples, which also replace various views, exist:

SPLIT32 (SDI)
COLLECT (MDI)
ENROLL (SDI)
VSWAP32 (SDI)
The following files are available for download from the Microsoft Download Center. Click the file names below to download the files:


Vwrplc32.exe

For more information about how to download files from the Microsoft Download Center, please visit the Download Center at the following Web address
http://www.microsoft.com/downloads/search.asp
and then click How to use the Microsoft Download Center.

NOTE: Use the -d option when running VWRPLC32.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
// thisfunction retrieves the current document from the active
// view.
if ((pCurrentView=GetActiveView())==NULL)
return FALSE;

// If we'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 additional information, please see the following article in the Microsoft Knowledge Base:

Q102829 Replacing a View in a CMDIChildWnd Window

Additional query words: MDI

Keywords : kbcode kbfile kbsample kbDocView kbMDI kbMFC kbVC400 kbVC500 kbVC600 kbGrpMFCATL
Version : winnt:4.0,4.1,4.2,5.0,6.0
Platform : winnt
Issue type :
Technology : kbvc


Last Reviewed: March 13, 2000
© 2000 Microsoft Corporation. All rights reserved. Terms of Use.




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[emmai]

GetParentFrame()->SetActiveView();
猜的。

[yangsaibing]

请高手指点