更新处理函数在对话框的菜单中不能工作

症状

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。

void CTestDlg::OnUpdateFileExit(CCmdUI* pCmdUI { pCmdUI->Enable(FALSE); //没有显示为禁用. 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 

1. 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()

 

1. 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; } }