基于对话框的MFC应用程序实现菜单的勾选功能

操作系统： Windows7/Windows10 64位

运行环境： Visual Studio 10

文件编码： Unicode

背景：

    在基于对话框的MFC应用程序中，给对话框建立一个菜单，让菜单选中后，对应的菜单项前显示“对勾”，但无法用ON_UPDATE_COMMAND_UI更新菜单。从命令用户界面处理函数(Command UIhandler)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。

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。MFCCFrameWnd::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的默认处理函数,该函数没有为菜单项调用更新命令处理函数。

解决办法：

          微软官方解决办法，点击打开链接：https://support.microsoft.com/en-us/kb/242577

在消息映射中添加消息：ON_WM_INITMENUPOPUP

BEGIN_MESSAGE_MAP(CTestDlg, CDialog)
//{{AFX_MSG_MAP(CTestDlg)
........................
........................
//}}AFX_MSG_MAP

ON_WM_INITMENUPOPUP()
END_MESSAGE_MAP()

在对话框类中添加OnInitMenuPopup成员函数，函数体复制下列代码即可

void CXXXDlg::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;
}
}

添加两个事件处理程序：消息类型分别是：COMMAND、UPDATE_COMMAND_UI 


实现两个消息处理程序

//ON_UPDATE_COMMAND_UI消息处理程序
void CXXXAppDlg::OnUpdateAutostartMenu(CCmdUI *pCmdUI)
{
// TODO: 在此添加命令更新用户界面处理程序代码
// 根据布尔类型成员变量设置菜单前是否显示选定标记.
pCmdUI->SetCheck(m_uCheckState);
}

//ON_COMMAND消息处理程序
void CXXXDlg::OnAutostartMenu()
{
// TODO: 在此添加命令处理程序代码
//单击菜单调用此函数，改变布尔类型成员变量的状态
m_uCheckState = !m_uCheckState;

//其它代码，菜单实现的功能
}

参考文章：

                                     
点击打开链接：在基于对话框的ＭＦＣ应用应用程序中，自己给对话框建立一个菜单，想让菜单选中后，对应的菜单项前显示