c++ - 使用 CreateTimerQueueTimer、Visual Studio 2012、C++ 创建计时器，定期运行

Question

我正在尝试使用 CreateTimerQueueTimer(...) 每隔一段时间运行一个函数。

我正在使用来自 MSDN 的示例，主要是这一行与我有关:

CreateTimerQueueTimer( &hTimer, hTimerQueue,(WAITORTIMERCALLBACK)TimerRoutine, &arg , 50,100, 0)

语法是:

BOOL WINAPI CreateTimerQueueTimer(
  _Out_     PHANDLE phNewTimer,
  _In_opt_  HANDLE TimerQueue,
  _In_      WAITORTIMERCALLBACK Callback,
  _In_opt_  PVOID Parameter,
  _In_      DWORD DueTime,
  _In_      DWORD Period,
  _In_      ULONG Flags
);

倒数第二个参数状态

Period [in]

The period of the timer, in milliseconds. If this parameter is zero, the timer is signaled once. If this parameter is greater than zero, the timer is periodic. A periodic timer automatically reactivates each time the period elapses, until the timer is canceled.

正如您在我的代码中看到的那样，我将到期时间设置为 50，将周期设置为 100。当我运行它时，它不会重复 触发计时器。有人可以帮我解决这个问题吗？

完整代码如下:

#include "stdafx.h"
#include <string>
#include <iostream>
#include <thread>
#include <Windows.h>
#include <stdio.h>

using namespace std;

HANDLE gDoneEvent;

VOID CALLBACK TimerRoutine(PVOID lpParam, BOOLEAN TimerOrWaitFired)
{
    if (lpParam == NULL)
    {
        printf("TimerRoutine lpParam is NULL\n");
    }
    else
    {
        // lpParam points to the argument; in this case it is an int

        printf("Timer routine called. Parameter is %d.\n", 
                *(int*)lpParam);
        if(TimerOrWaitFired)
        {
            printf("The wait timed out.\n");
        }
        else
        {
            printf("The wait event was signaled.\n");
        }
    }

    SetEvent(gDoneEvent);
}

int main()
{
    HANDLE hTimer = NULL;
    HANDLE hTimerQueue = NULL;
    int arg = 123,x;


    // Use an event object to track the TimerRoutine execution
    gDoneEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
    if (NULL == gDoneEvent)
    {
        printf("CreateEvent failed (%d)\n", GetLastError());
        return 1;
    }

    // Create the timer queue.
    hTimerQueue = CreateTimerQueue();
    if (NULL == hTimerQueue)
    {
        printf("CreateTimerQueue failed (%d)\n", GetLastError());
        return 2;
    }

    // Set a timer to call the timer routine in 10 seconds.
    if (!CreateTimerQueueTimer( &hTimer, hTimerQueue,(WAITORTIMERCALLBACK)TimerRoutine, &arg , 50,100, 0))
    {
        printf("CreateTimerQueueTimer failed (%d)\n", GetLastError());
        return 3;
    }

    // TODO: Do other useful work here 

    printf("Call timer routine in 10 seconds...\n");

    // Wait for the timer-queue thread to complete using an event 
    // object. The thread will signal the event at that time.

    if (WaitForSingleObject(gDoneEvent, INFINITE) != WAIT_OBJECT_0)
        printf("WaitForSingleObject failed (%d)\n", GetLastError());

    CloseHandle(gDoneEvent);

    // Delete all timers in the timer queue.
    if (!DeleteTimerQueue(hTimerQueue))
        printf("DeleteTimerQueue failed (%d)\n", GetLastError());
    cin>>x;
    return 0;
}

谢谢

Answer 1

事件 gDoneEvent 在函数 TimerRoutine() 退出之前发出信号。对于回调函数的重复调用，在函数 TimerRoutine() 被调用所需次数后，向事件 gDoneEvent 发出信号。

可以包含以下代码行。

static int count = 0;

VOID CALLBACK TimerRoutine(PVOID lpParam, BOOLEAN TimerOrWaitFired)
{
    ......
    count++;
    if(count == 100)
    {
         SetEvent(gDoneEvent);
    }
}