我的 C++ 应用程序有一个无窗口计时器，用于定期清理从未(也永远不会)完全处理的潜在通信数据。问题是永远不会调用回调函数。我的类构造函数在返回之前执行以下代码:

    if ( (this->m_hMsgsThread = ::CreateThread(
        NULL,                           // no security attributes
        0,                              // use default initial stack size
        reinterpret_cast<LPTHREAD_START_ROUTINE>(MessagesThreadFn), // function to execute in new thread
        this,                           // thread parameters
        0,                              // use default creation settings
        NULL                            // thread ID is not needed
        )) == NULL )
    {
        dwError = ::GetLastError();
        TRACE(_T("%s : Failed to create thread.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), _T(__FUNCTION__), dwError, _T(__FILE__), __LINE__);
        continue;
    }

    if ( (s_pCleanupTimerId = ::SetTimer( NULL, 0, MSGS_CLEANUP_PERIOD, CleanupTimerProc )) == NULL )
    {
        dwError = ::GetLastError();
        TRACE(_T("%s : Failed to create timer.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), _T(__FUNCTION__), dwError, _T(__FILE__), __LINE__);
        continue;
    }

这是我对 CleanupTimerProc 的定义:

static void CALLBACK CleanupTimerProc( HWND hwnd, UINT uMsg, UINT_PTR idEvent, DWORD dwTime )
{
    CMsgDesc * pobjMsgDesc = NULL;
    DWORD dwError = ERROR_SUCCESS;
    DWORD dwItem;
    DWORD dwList;
    DWORD dwListItems;
    DWORD dwThen, dwNow;
    const DWORD cMAX_LISTS = MSGS_MAX_EVENTS;

    do
    {
        // Kill off the old timer.
        TRACE(_T("%s : Killing cleanup timer.\r\n"), _T(__FUNCTION__));
        ASSERT(s_pCleanupTimerId == idEvent);
        ::KillTimer( hwnd, idEvent );

        // Start a new timer using the same ID.
        TRACE(_T("%s : Restarting cleanup timer.\r\n"), _T(__FUNCTION__));
        if ( (s_pCleanupTimerId = ::SetTimer( NULL, 0, MSGS_CLEANUP_PERIOD, CleanupTimerProc )) == NULL )
        {
            dwError = ::GetLastError();
            TRACE(_T("%s : Failed to create timer.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), _T(__FUNCTION__), dwError, _T(__FILE__), __LINE__);
            continue;
        }

        // Get the current time.
        dwNow = ::GetTickCount();

        // Search through the message descriptor lists
        // looking for descriptors that haven't been touched in a while.
        TRACE(_T("%s : Deleting old message descriptors.\r\n"), _T(__FUNCTION__));
        ASSERT(s_pInterface != NULL);
        ASSERT(s_pInterface->pobjMessages != NULL);
        ::EnterCriticalSection( &s_pInterface->pobjMessages->m_csMsgDescriptors );
        for ( dwList = 0; dwList < cMAX_LISTS; dwList++ )
        {
            dwListItems = s_pInterface->pobjMessages->m_pobjMsgDescriptors[dwList]->GetItemCount();

            for ( dwItem = 0; dwItem < dwListItems; dwItem++ )
            {
                if ( (pobjMsgDesc = (CMsgDesc *)s_pInterface->pobjMessages->m_pobjMsgDescriptors[dwList]->Peek( NULL, dwItem )) == NULL )
                {
                    dwError = ::GetLastError();
                    TRACE(_T("%s : Failed to peek item from list.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), _T(__FUNCTION__), dwError, _T(__FILE__), __LINE__);
                    continue;
                }

                // Get the last touched time from the descriptor.
                dwThen = pobjMsgDesc->m_dwLastTouched;

                // If the specified time has elapsed, delete the descriptor.
                if ( (dwNow - dwThen) > MSGS_DESC_SHELFLIFE )
                {
                    if ( s_pInterface->pobjMessages->m_pobjMsgDescriptors[dwList]->Remove( NULL, dwItem ) == NULL )
                    {
                        dwError = ::GetLastError();
                        TRACE(_T("%s : Failed to remove item from list.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), _T(__FUNCTION__), dwError, _T(__FILE__), __LINE__);
                        continue;
                    }

                    delete pobjMsgDesc;
                    TRACE(_T("%s : Deleted old message descriptor.\r\n"), _T(__FUNCTION__));
                }
            }
        }
        ::LeaveCriticalSection( &s_pInterface->pobjMessages->m_csMsgDescriptors );
    }
    while ( 0 );
}

关于为什么这个函数没有被调用有什么想法吗？我需要在线程内创建计时器吗？

最佳答案

我可能记错了....

然而，计时器仍然需要 Windows 消息泵。如果您希望该计时器在给定线程中触发，则该线程需要发送消息，否则它永远不会被调用。

同样，在我看来，您正在创建一个进入无限循环的计时器回调。该函数需要退出，否则永远无法调用下一个计时器。

关于c++ - 永远不会调用 SetTimer 回调，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/7250034/