为什么我用GetActiveView却得不到View呢

为什么我用GetActiveView却得不到View呢？
看一下这段代码！void CMainFrame::OnViewSwitch(int iChangeView)
{
static CView* pOldView = GetActiveView();
ASSERT_VALID(pOldView);
static CView* pNewView = NULL; if(iChangeView == 0)
{
pNewView = (CView*)new CHtmView;
}
else
{
pNewView = (CView*)new CMyView;
} ASSERT_VALID(pNewView);
CCreateContext context;
context.m_pCurrentDoc = pOldView->GetDocument();
pNewView->Create(NULL, NULL, WS_BORDER|WS_CHILD, CFrameWnd::rectDefault,this, iChangeView ,&context);
pNewView->OnInitialUpdate(); SetActiveView(pNewView);
pNewView->ShowWindow(SW_SHOW);
pOldView->ShowWindow(SW_HIDE); delete pOldView;
RecalcLayout();
}