现象展示：

具体原因：

A button in a CDialogBar object is disabled automatically if the command routing does not contain a command handler function for the button.
To enable a button in a CDialogBar object, the command routing must include a command handler for the button.

NOTE: Because the CDialogBar object is not included in the routing scheme, the ON_BN_CLICKED() or ON_COMMAND() handler must be placed in one of the objects mentioned above that is in the routing scheme and not in the CDialogBar class.

解决办法：

1、如果按钮的消息处理是在CMainFrame中的就不用OnUpdateCmdUI，在其他类的话还是要重载OnUpdateCmdUI的

2、重载CMainFrame::OnCmdMsg函数

BOOL CMainFrame::OnCmdMsg(UINT nID, int nCode, void* pExtra, AFX_CMDHANDLERINFO* pHandlerInfo)

{

    if(m_wndDlgBar.OnCmdMsg(nID, nCode, pExtra, pHandlerInfo))

    {

        return TRUE;

    }

    return CMDIFrameWndEx::OnCmdMsg(nID, nCode, pExtra, pHandlerInfo);

}

3、重载CDialogBar::OnUpdateCmdUI

void CMyDialogBar::OnUpdateCmdUI(CFrameWnd* pTarget, BOOL bDisableIfNoHandler)

{

    CDialogBar::OnUpdateCmdUI(pTarget, FALSE);

}