MFC 如何启用/禁用菜单（返灰/不可点击状态）

1、为页面（窗口）添加一个菜单栏和子菜单

2、在XXDlg.h文件中定义一个菜单栏变量和bool变量

CMenu m_Menu;	//菜单变量
bool m_EnableMenu;//菜单栏中某个子菜单禁用/启用（变灰）的控制变量

3、在OnInitDialog函数中进行初始化：（即将菜单栏植入主界面）

m_Menu.LoadMenu(IDR_MENU_MAIN);//菜单栏的ID
SetMenu(&m_Menu);//添加入到界面
m_EnableMenu =false;//初始化为禁用子菜单

4、添加菜单ID的ON_UPDATE_COMMAND_UI消息，点击菜单，在子菜单上右键点击，添加事件处理程序，选择你的对话框类，在左边的消息类型中选择UPDATE_COMMAND_UI添加如下代码：

void CXXDlg::OnUpdateDisconnectAll(CCmdUI *pCmdUI)
{
	pCmdUI->Enable(m_EnableMenu); //m_EnableMenu的值对应禁用和启用，1是启用，0是禁用
} 

根据网上资料，对于视图文档类MFC程序，在主框架类CMainFrame的构造函数中把成员变量m_bAutoMenuEnable=FALSE就可以解决问题了。但是基于对话框的MFC应用程序没有m_bAutoMenuEnable变量。解决方法：

5、在对话框类的消息中加入OnInitMenuPopup（）消息：

消息函数内重载如下：

void CXXXDlg::OnInitMenuPopup(CMenu* pPopupMenu, UINT nIndex, BOOL bSysMenu)
{
     CDialog::OnInitMenuPopup(pPopupMenu, nIndex, bSysMenu);

   	// TODO: 在此处添加消息处理程序代码
   
	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;
	}
}

如果想在其他程序中改变菜单的启用/禁用属性，改变m_EnableMenu的值即可实现。