ew);

       }



       // update frame counts and frame title (may already have been visible)

       if (pDoc != NULL)

              pDoc->UpdateFrameCounts();

       OnUpdateFrameTitle(TRUE);

}

上面的函数中对视图的操作主要是用SetActiveView设置了活动视图，并且调用了视图的OnActivateFrame函数。在CFrameWnd类中维护着一个保护成员：CView* m_pViewActive;，SetAcitveView函数主要就是对它进行操作：

void CFrameWnd::SetActiveView(CView* pViewNew, BOOL bNotify)

{

       CView* pViewOld = m_pViewActive;

       if (pViewNew == pViewOld)

              return;     // do not re-activate if SetActiveView called more than once



       m_pViewActive = NULL;   // no active for the following processing



       // deactivate the old one

       if (pViewOld != NULL)

              pViewOld->OnActivateView(FALSE, pViewNew, pViewOld);



       if (m_pViewActive != NULL)

              return;     // already set

       m_pViewActive = pViewNew;



       // activate

       if (pViewNew != NULL && bNotify)

              pViewNew->OnActivateView(TRUE, pViewNew, pViewOld);

}

CFrameWnd还有另一个函数返回这个成员：

CView* CFrameWnd::GetActiveView() const

{

       ASSERT(m_pViewActive == NULL ||

              m_pViewActive->IsKindOf(RUNTIME_CLASS(CView)));

       return m_pViewActive;

}

CframeWnd还有一个函数能取得当前活动的文档，它是通过活动视图间接得到的：

CDocument* CFrameWnd::GetActiveDocument()

{

       ASSERT_VALID(this);

       CView* pView = GetActiveView();

       if (pView != NULL)

              return pView->GetDocument();

       return NULL;

}

（五）MDI主窗口和子窗口之间的关联：

在MDI子窗口创建的时候，指定了它与MDI之间的关系：

BOOL CMDIChildWnd::Create(LPCTSTR lpszClassName,

       LPCTSTR lpszWindowName, DWORD dwStyle,

       const