让对话框对UPDATE_COMMAND_UI生效

问题：一般情况下我们用UPDATE_COMMAND_UI来修改菜单的状态(enable/disable, check/uncheck, change text)，但这个方法在一个基于对话框上的菜单却没有效果。
void CTestDlg::OnUpdateFileExit(CCmdUI* pCmdUI)
{
     pCmdUI->Enable(FALSE);
     pCmdUI->SetCheck(TRUE);
     pCmdUI->SetRadio(TRUE);
     pCmdUI->SetText("Close");
//以上方法在MDI、SDI程序中都能起作用，在对话框中却没有效果,根本没有调用这个函数。
}
 
原因分析：当显示一个下拉的菜单的时候，在显示菜单前会发送WM_INITMENUPOPUP消息。而CFrameWnd::OnInitMenuPopup函数会刷新这个菜单项，同时如果有UPDATE_COMMAND_UI响应函数，则调用它。通过它来更新反应每个菜单的外观效果(enabled/disabled, checked/unchecked).
在一个基于对话框的程序中，因为没有OnInitMenuPopup函数，所以不会调用UPDATE_COMMAND_UI响应函数，而是使用了CWnd类的默认处理, 这种处理没有调用UPDATE_COMMAND_UI响应函数。

解决方法如下：
第一步：
在对话框类的.cpp文件，添加一个ON_WM_INITMENUPOPUP入口到消息映射里面
BEGIN_MESSAGE_MAP(CTestDlg, CDialog)
//}}AFX_MSG_MAP
ON_WM_INITMENUPOPUP()
END_MESSAGE_MAP()
第二步：
在对话框类的.h文件添加消息函数声明。
// Generated message map functions
//{{AFX_MSG(CDisableDlgMenuDlg)
afx_msg void OnInitMenuPopup(CMenu *pPopupMenu, UINT nIndex,BOOL bSysMenu);
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
第三步：
在对话框类的.cpp文件添加如下函数代码(大部分代码取自WinFrm.cpp文件的函数CFrameWnd::OnInitMenuPopup):
void C******Dlg::OnInitMenuPopup(CMenu *pPopupMenu, UINT nIndex,BOOL bSysMenu)
{
     ASSERT(pPopupMenu != NULL);
    // Check the enabled state of various menu items.

    CCmdUI state;
    state.m_pMenu = pPopupMenu;
    ASSERT(state.m_pOther == NULL);
    ASSERT(state.m_pParentMenu == NULL);

    // Determine if menu is popup in top-level menu and set m_pOther to
    // it if so (m_pParentMenu == NULL indicates that it is secondary popup).
    HMENU hParentMenu;
    if (AfxGetThreadState()->m_hTrackingMenu == pPopupMenu->m_hMenu)
         state.m_pParentMenu = pPopupMenu;??? // Parent == child for tracking popup.
   else if ((hParentMenu = ::GetMenu(m_hWnd)) != NULL)
   {
       CWnd* pParent = this;
       // Child windows don't have menus--need to go to the top!
       if (pParent != NULL &&
(hParentMenu = ::GetMenu(pParent->m_hWnd)) != NULL)
      {
           int nIndexMax = ::GetMenuItemCount(hParentMenu);
          for (int nIndex = 0; nIndex < nIndexMax; nIndex++)
         {
             if (::GetSubMenu(hParentMenu, nIndex) == pPopupMenu->m_hMenu)
             {
                // When popup is found, m_pParentMenu is containing menu.
                state.m_pParentMenu = CMenu::FromHandle(hParentMenu);
                break;
             }
         }
    }
}

  state.m_nIndexMax = pPopupMenu->GetMenuItemCount();
  for (state.m_nIndex = 0; state.m_nIndex < state.m_nIndexMax;
  state.m_nIndex++)
  {
      state.m_nID = pPopupMenu->GetMenuItemID(state.m_nIndex);
      if (state.m_nID == 0)
          continue; // Menu separator or invalid cmd - ignore it.

      ASSERT(state.m_pOther == NULL);
      ASSERT(state.m_pMenu != NULL);
      if (state.m_nID == (UINT)-1)
      {
          // Possibly a popup menu, route to first item of that popup.
          state.m_pSubMenu = pPopupMenu->GetSubMenu(state.m_nIndex);
          if (state.m_pSubMenu == NULL ||
 (state.m_nID = state.m_pSubMenu->GetMenuItemID(0)) == 0 ||
state.m_nID == (UINT)-1)
       {
              continue;    // First item of popup can't be routed to.
       }
       state.DoUpdate(this, TRUE);?? // Popups are never auto disabled.
      }
      else
     {
          // Normal menu item.
          // Auto enable/disable if frame window has m_bAutoMenuEnable
          // set and command is _not_ a system command.
         state.m_pSubMenu = NULL;
         state.DoUpdate(this, FALSE);
      }

      // Adjust for menu deletions and additions.
      UINT nCount = pPopupMenu->GetMenuItemCount();
      if (nCount < state.m_nIndexMax)
        {
                   state.m_nIndex -= (state.m_nIndexMax - nCount);
                   while (state.m_nIndex < nCount &&
                  pPopupMenu->GetMenuItemID(state.m_nIndex) == state.m_nID)
           {
            state.m_nIndex++;
            }
       }
        state.m_nIndexMax = nCount;
   }
}

更详细的信息可参考
http://support.microsoft.com/default.aspx?scid=kb;en-us;242577