模态对话框启动时的延迟显示

 在网上搜索了一下，似乎没有完整的解决方案。

本人经过查看MFC源代码，找到了一个解决方案。

 

1、首先，在资源中，将对话框的WS_VISIBLE属性去掉。

2、重载DoModal以及RunModalLoop函数。具体代码如下：

int CTestDlgDlg::DoModal() {  // TODO: Add your specialized code here and/or call the base class    // can be constructed with a resource template or InitModalIndirect  ASSERT(m_lpszTemplateName != NULL || m_hDialogTemplate != NULL ||   m_lpDialogTemplate != NULL);    // load resource as necessary  LPCDLGTEMPLATE lpDialogTemplate = m_lpDialogTemplate;  HGLOBAL hDialogTemplate = m_hDialogTemplate;  HINSTANCE hInst = AfxGetResourceHandle();  if (m_lpszTemplateName != NULL)  {   hInst = AfxFindResourceHandle(m_lpszTemplateName, RT_DIALOG);   HRSRC hResource = ::FindResource(hInst, m_lpszTemplateName, RT_DIALOG);   hDialogTemplate = LoadResource(hInst, hResource);  }  if (hDialogTemplate != NULL)   lpDialogTemplate = (LPCDLGTEMPLATE)LockResource(hDialogTemplate);    // return -1 in case of failure to load the dialog template resource  if (lpDialogTemplate == NULL)   return -1;    // disable parent (before creating dialog)  HWND hWndParent = PreModal();  AfxUnhookWindowCreate();  BOOL bEnableParent = FALSE;  if (hWndParent != NULL && ::IsWindowEnabled(hWndParent))  {   ::EnableWindow(hWndParent, FALSE);   bEnableParent = TRUE;  }    TRY  {   // create modeless dialog   AfxHookWindowCreate(this);   if (CreateDlgIndirect(lpDialogTemplate,    CWnd::FromHandle(hWndParent), hInst))   {    if (m_nFlags & WF_CONTINUEMODAL)    {     // enter modal loop     DWORD dwFlags = MLF_SHOWONIDLE;     if (GetStyle() & DS_NOIDLEMSG)      dwFlags |= MLF_NOIDLEMSG;     VERIFY(MyRunModalLoop(dwFlags) == m_nModalResult);    }        // hide the window before enabling the parent, etc.    if (m_hWnd != NULL)     SetWindowPos(NULL, 0, 0, 0, 0, SWP_HIDEWINDOW|     SWP_NOSIZE|SWP_NOMOVE|SWP_NOACTIVATE|SWP_NOZORDER);   }  }  CATCH_ALL(e)  { #ifndef DELETE_EXCEPTION #define DELETE_EXCEPTION(e) do { e->Delete(); } while (0) #endif   DELETE_EXCEPTION(e);   m_nModalResult = -1;  }  END_CATCH_ALL      if (bEnableParent)    ::EnableWindow(hWndParent, TRUE);   if (hWndParent != NULL && ::GetActiveWindow() == m_hWnd)    ::SetActiveWindow(hWndParent);      // destroy modal window   DestroyWindow();   PostModal();      // unlock/free resources as necessary   if (m_lpszTemplateName != NULL || m_hDialogTemplate != NULL)    UnlockResource(hDialogTemplate);   if (m_lpszTemplateName != NULL)    FreeResource(hDialogTemplate);      return m_nModalResult; }

int CTestDlgDlg::MyRunModalLoop(DWORD dwFlags) {  ASSERT(::IsWindow(m_hWnd)); // window must be created  ASSERT(!(m_nFlags & WF_MODALLOOP)); // window must not already be in modal state    // for tracking the idle time state  BOOL bIdle = TRUE;  LONG lIdleCount = 0;  BOOL bShowIdle = (dwFlags & MLF_SHOWONIDLE) && !(GetStyle() & WS_VISIBLE);  HWND hWndParent = ::GetParent(m_hWnd);  m_nFlags |= (WF_MODALLOOP|WF_CONTINUEMODAL);  MSG* pMsg = &AfxGetThread()->m_msgCur;    // acquire and dispatch messages until the modal state is done  for (;;)  {   ASSERT(ContinueModal());      // phase1: check to see if we can do idle work   while (bIdle &&    !::PeekMessage(pMsg, NULL, NULL, NULL, PM_NOREMOVE))   {    ASSERT(ContinueModal());        // show the dialog when the message queue goes idle    if (m_bShowModal)    {     ShowWindow(SW_SHOWNORMAL);     UpdateWindow();     m_bShowModal = FALSE;    }        // call OnIdle while in bIdle state    if (!(dwFlags & MLF_NOIDLEMSG) && hWndParent != NULL && lIdleCount == 0)    {     // send WM_ENTERIDLE to the parent     ::SendMessage(hWndParent, WM_ENTERIDLE, MSGF_DIALOGBOX, (LPARAM)m_hWnd);    }    if ((dwFlags & MLF_NOKICKIDLE) ||     !SendMessage(WM_KICKIDLE, MSGF_DIALOGBOX, lIdleCount++))    {     // stop idle processing next time     bIdle = FALSE;    }   }      // phase2: pump messages while available   do   {    ASSERT(ContinueModal());        // pump message, but quit on WM_QUIT    if (!AfxGetThread()->PumpMessage())    {     AfxPostQuitMessage(0);     return -1;    }        // show the window when certain special messages rec'd    if (m_bShowModal &&     (pMsg->message == 0x118 || pMsg->message == WM_SYSKEYDOWN))    {     OutputDebugString(_T("Show2"));     ShowWindow(SW_SHOWNORMAL);     UpdateWindow();     m_bShowModal = FALSE;    }        if (!ContinueModal())     goto ExitModal;        // reset "no idle" state after pumping "normal" message    if (AfxGetThread()->IsIdleMessage(pMsg))    {     bIdle = TRUE;     lIdleCount = 0;    }       } while (::PeekMessage(pMsg, NULL, NULL, NULL, PM_NOREMOVE));  }   ExitModal:  m_nFlags &= ~(WF_MODALLOOP|WF_CONTINUEMODAL);  return m_nModalResult;

}

注意红字部分，定义了m_bShowModal变量，默认为FALSE。

经过以上代码，启动对话框后，是不会显示出来的。若想显示对话框，可以通过调用

  m_bShowModal = TRUE;   PostMessage(WM_NULL);

以上代码，只要有一些MFC基础的人，都可以看懂。