CWnd::GetActiveWindow
Retrieves a pointer to the active window.
static CWnd* PASCAL GetActiveWindow( );
CFrameWnd::GetActiveView CMainFrame独有的函数。
Call this member function to obtain a pointer to the active view (if any) attached to a frame window (CFrameWnd).
CView* GetActiveView( ) const;
via:http://msdn.microsoft.com/en-US/library/zs0t7t34(v=VS.80).aspx