// The following example toggles two views in an SDI (single document
// interface) frame window. A design decision must be made as to
// whether to leave the inactive view connected to the document,
// such that the inactive view continues to receive OnUpdate
// notifications from the document. It is usually desirable to
// keep the inactive view continuously in sync with the document, even
// though it is inactive. However, doing so incurs a performance cost,
// as well as the programming cost of implementing OnUpdate hints.
// It may be less expensive, in terms of performance and/or programming,
// to re-sync the inactive view with the document only with it is
// reactivated. This example illustrates this latter approach, by
// reconnecting the newly active view and disconnecting the newly
// inactive view, via calls to CDocument::AddView and RemoveView.
BOOL CMainFrame::OnViewChange(UINT nCmdID)
// There is an ON_COMMAND_RANGE message map entry associated with
// OnViewChange:
// ON_COMMAND_RANGE( ID_VIEW_VIEW1, ID_VIEW_VIEW2, OnViewChange)
{
CView* pViewAdd;
CView* pViewRemove;
CDocument* pDoc = GetActiveDocument();
if((nCmdID == ID_VIEW_VIEW1) && (m_currentView == 1))
return;
if((nCmdID == ID_VIEW_VIEW2) && (m_currentView == 2))
return;
if (nCmdID == ID_VIEW_VIEW2)
{
if (m_pView2 == NULL)
{
m_pView1 = GetActiveView();
m_pView2 = new CMyView2;
//Note that if OnSize has been overridden in CMyView2
//and GetDocument() is used in this override it can
//cause assertions and, if the assertions are ignored,
//cause access violation.
m_pView2->Create(NULL, NULL, AFX_WS_DEFAULT_VIEW,
rectDefault, this, AFX_IDW_PANE_FIRST + 1, NULL);
}
pViewAdd = m_pView2;
pViewRemove = m_pView1;
m_currentView= 2;
}
else
{
pViewAdd = m_pView1;
pViewRemove = m_pView2;
m_currentView= 1;
}
// Set the child i.d. of the active view to AFX_IDW_PANE_FIRST,
// so that CFrameWnd::RecalcLayout will allocate to this
// "first pane" that portion of the frame window's client area
// not allocated to control bars. Set the child i.d. of the
// other view to anything other than AFX_IDW_PANE_FIRST; this
// examples switches the child id's of the two views.
int nSwitchChildID = pViewAdd->GetDlgCtrlID();
pViewAdd->SetDlgCtrlID(AFX_IDW_PANE_FIRST);
pViewRemove->SetDlgCtrlID(nSwitchChildID);
// Show the newly active view and hide the inactive view.
pViewAdd->ShowWindow(SW_SHOW);
pViewRemove->ShowWindow(SW_HIDE);
// Connect the newly active view to the document, and
// disconnect the inactive view.
pDoc->AddView(pViewAdd);
pDoc->RemoveView(pViewRemove);
SetActiveView(pViewAdd);
RecalcLayout();
}
