windows - 了解 MsgWaitForMultipleObjects

Question

我有一个主要的 gui 线程，我想在后台线程执行某些任务时保持对用户操作的响应，例如移动对话框、调整大小等。过去，我使用带有超时的 WaitForSingleObject 来处理 gui 事件，同时等待后台线程完成。我最近读到有关 MsgWaitForMultipleObjects 的信息，它看起来正在解决我的问题，让我变得更干净一些。

有人能告诉我以下代码中的错误以及我哪里出错了吗？当我单击按钮启动线程时，GUI 没有响应。我制作了一个带有在主 ui 线程上播放的 avi 的对话框应用程序。我有一个按钮来启动线程并使用 MsgWaitForMultipleObjects 等待线程句柄，但允许处理所有消息，最终在线程完成/发出信号时中断。

谢谢。

UINT MyThreadProc( LPVOID pParam )
{
    ThreadData* pObject = (ThreadData*)pParam;

    if (pObject == NULL ||
        !pObject->IsKindOf(RUNTIME_CLASS(ThreadData)))
    return 1;   

    // Do some processing.
    int x = 0; 
    while (x++ < 5000)
    {
        for (int i=0; i<50000; i++)
            double sum = sqrt((double)i+1) * sqrt((double)i+2); 
    }

    return 0;
}

按钮处理程序

void Cmsgwait_demoDlg::OnBnClickedBtnStartThread()
{
    m_pThreadData = new ThreadData;
    CWinThread* pWorkThread = AfxBeginThread(MyThreadProc, m_pThreadData);

    m_status.SetWindowText("Status: Waiting for thread to complete."); 

    HANDLE handles[] = { pWorkThread->m_hThread }; 
    DWORD ret = 0; 

    do 
    {
        ret = MsgWaitForMultipleObjects(1, handles, FALSE, INFINITE, QS_ALLINPUT); 
        if (ret == WAIT_OBJECT_0)
        {
            m_status.SetWindowText("Status: Thread completed."); 
        }
        else if (WAIT_IO_COMPLETION)
        {
            m_status.SetWindowText("Status: User mode APC queued."); 
        }
        else if (WAIT_FAILED)
        {
            m_status.SetWindowText("Status: Wait failed"); 
        }
    }
    while (ret != WAIT_OBJECT_0 && ret != WAIT_FAILED);
}

Answer 1

您没有处理 UI 线程的传入消息，取 look at Raymond's blog (另见 here )示例。

  while (true) {
    switch (MsgWaitForMultipleObjects(1, &h,
                         FALSE, INFINITE, QS_ALLINPUT)) {
    case WAIT_OBJECT_0:
      DoSomethingWith(h); // event has been signalled
      break;
    case WAIT_OBJECT_0+1:
      // we have a message - peek and dispatch it
      while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
        // TODO:  must handle WM_QUIT; see Raymond's blog for details
        TranslateMessage(&msg);
        DispatchMessage(&msg);
      }
      break;
    default:
      return FALSE; // unexpected failure
    }
  }