To fully understand what follows, some previous knowledge is required, namely how MFC creates documents, frame windows and views using document templates and how their relationship is maintained in the program. A previous article showing how to replace views in non-OLE applications is a recommended reading.
First of all, let's understand how the framework creates OLE frames. When a server object is inserted in a container, a document, a frame window and a view contained within it (or multiple views, if it is a splitter) are first constructed, following common document-template procedures. After that, in response to the OLEIVERB_SHOW
OLE verb, the COleServerDoc::ActivateInPlace
function is called. If there is no previous OLE frame (i.e. it is the first time it will be activated), the OLE frame is created, calling the COleServerDoc::CreateInPlaceFrame
function. Here, not only the OLE frame is created (using the CDocTemplate::CreateOleFrame
function), but also the view in the previously constructed frame window is "connected" to the newly created OLE frame. If the original frame was a splitter, then the view in the first pane is used. The "connection" process consists on changing the view's parent window to the new frame. It is performed calling the COleServerDoc::ConnectView
function. The active view on the original frame window is kept (using the m_pActiveView
member), because some controls continue to send notification messages to their original parent window. These notification messages should be handled in the original frame window. Once the OLE frame is created and a view is "connected" to it, then it is activated.
Now, if we want to replace a view in an OLE frame, we have to replace it in 2 frame windows: the OLE frame and the original frame. The current active view should be destroyed, a new view should be created within the original frame and be later connected to the OLE frame. The active views should be set to NULL
first, so no Windows message could be sent by the framework to a non-valid view stored in the m_pActiveView
member of the frame windows.
To perform this, we need a method in our document class, which should receive the new view type as a parameter and return a success flag. The advantage of having this method in the document class becomes obvious when there are several document types each of which can have different view types. Note that the document should be a COleServerDoc
descendant. This is how it is done:
BOOL CMyDoc::InPlaceSwitchToView ( CRuntimeClass *pNewViewClass )
{
CFrameWnd* pFrame = (CFrameWnd *)m_pOrigParent;
View* pOldActiveView = m_pInPlaceFrame->GetActiveView();
if (pOldActiveView->IsKindOf(pNewViewClass))
return TRUE;
pFrame->SetActiveView(NULL);
m_pInPlaceFrame->SetActiveView(NULL);
BOOL bAutoDelete = m_bAutoDelete;
m_bAutoDelete = FALSE;
pOldActiveView->DestroyWindow();
m_bAutoDelete = bAutoDelete;
CView* pNewView = (CView *)pNewViewClass->CreateObject();
if (pNewView == NULL)
{
TRACE1("Warning: Dynamic create of view type %Fs failed\n",
pNewViewClass->m_lpszClassName);
return FALSE;
}
CCreateContext context;
context.m_pNewViewClass = pNewViewClass;
context.m_pCurrentDoc = this;
context.m_pNewDocTemplate = NULL;
context.m_pLastView = NULL;
context.m_pCurrentFrame = pFrame;
if (!pNewView->Create(NULL, NULL, AFX_WS_DEFAULT_VIEW, CRect(0, 0, 0, 0),
pFrame, AFX_IDW_PANE_FIRST, &context))
{
TRACE0("Warning: couldn't create view for frame\n");
delete pNewView;
return FALSE;
}
pFrame->SetActiveView(pNewView);
ConnectView(m_pInPlaceFrame, pNewView);
pNewView->ModifyStyleEx(WS_EX_CLIENTEDGE, 0, SWP_DRAWFRAME);
pNewView->SendMessage(WM_INITIALUPDATE, 0, 0);
pNewView->UpdateWindow();
return TRUE;
}
Now that we have a method in our document class that will replace the current view in an OLE frame, let's use it. The new view type should be decided (in response to a menu selection, for instance), and the function must be called as follows:
CRuntimeClass* pNewViewClass = RUNTIME_CLASS(CMyView);
if (!InPlaceSwitchToView(pNewViewClass))
else
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