基于对话框程序用ON_UPDATE_COMMAND_UI更新菜单

从命令用户界面处理函数(Command UI handler)改变菜单状态(启用/禁用,选择/取消选择,更改文字)在由对话框处理时没有正常工作。

比如：

void CTestDlg::OnUpdateFileExit(CCmdUI* pCmdUI){    .    pCmdUI->SetCheck(TRUE); // 没有文字前显示选定标记.    pCmdUI->SetRadio(TRUE); // 没有在文字前显示点.    pCmdUI->SetText("Close"); //没有更改菜单文字.} 

原因
在下拉菜单显示的时候, WM_INITMENUPOPUP消息被先发送以显示菜单项。MFC CFrameWnd::OnInitMenuPopup 函数遍历菜单项并为每个菜单项调用更新命令处理函数（如果有的话）.菜单的外观被更新以反映它的状态（启用/禁用,选择/取消选择）
更新用户界面机制在基于对话框的应用程序中不能工作，因为CDialog没有OnInitMenuPopup 处理函数，而使用CWnd's 默认处理函数,该函数没有为菜单项调用更新命令处理函数。

 

解决
适用下列步骤解决此问题

在消息映射中添加ON_WM_INITMENUPOPUP 项: BEGIN_MESSAGE_MAP(CTestDlg, CDialog) //{{AFX_MSG_MAP(CTestDlg)                        ........................                        ........................ //}}AFX_MSG_MAP ON_WM_INITMENUPOPUP()END_MESSAGE_MAP() 在你的对话框类中添加OnInitMenuPopup成员函数且复制下列代码到该函数（注意：代码基本上是从CFrameWnd::OnInitMenuPopup（在WinFrm.cpp中)复制过来的）: void CTestDlg::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;    }} 

 

之后就可以在UI——UPDATE函数中更新了。