WaitForSingleObject 立即发出信号

Question

我正在尝试唤醒我的电脑以防它进入睡眠模式。我在某个网站上找到了这段代码片段，但我在最后添加的 Messagebox 总是立即 returns。

我还在我的系统中启用了电源选项中的唤醒定时器。

[DllImport("kernel32.dll")]
    public static extern IntPtr CreateWaitableTimer(IntPtr lpTimerAttributes,
    bool bManualReset, string lpTimerName);

    [DllImport("kernel32.dll")]
    public static extern bool SetWaitableTimer(IntPtr hTimer, [In] ref long
    pDueTime, int lPeriod, IntPtr pfnCompletionRoutine, IntPtr
    lpArgToCompletionRoutine, bool fResume);

    [DllImport("kernel32", SetLastError = true, ExactSpelling = true)]
    public static extern Int32 WaitForSingleObject(IntPtr handle, uint
    milliseconds);

    static IntPtr handle;

    private void SetWaitForWakeUpTime()
    {
        long duetime = 1200000000;
        handle = CreateWaitableTimer(IntPtr.Zero, true, "MyWaitabletimer");
        SetWaitableTimer(handle, ref duetime, 0, IntPtr.Zero, IntPtr.Zero, true);
        uint INFINITE = 0xFFFFFFFF;
        int ret = WaitForSingleObject(handle, INFINITE);
        MessageBox.Show("wake up !");
    }

我这样称呼它：

private void buttonTest_Click(object sender, EventArgs e)
    {
        SetWaitForWakeUpTime();
    }

理论上这应该只在 2 分钟后发出信号，对吧？为什么立即发出信号，我该如何纠正？

Answer 1

SetWaitableTimer() 可以在绝对时间和增量时间上触发。来自 MSDN 文章：

pDueTime [in]
The time after which the state of the timer is to be set to signaled, in 100 nanosecond intervals. Use the format described by the FILETIME structure. Positive values indicate absolute time. Be sure to use a UTC-based absolute time, as the system uses UTC-based time internally. Negative values indicate relative time. The actual timer accuracy depends on the capability of your hardware. For more information about UTC-based time, see System Time.

现在您使用了一个正值，所以您指定了 1600 年的日期，它总是立即完成。看起来你的实际意图是使用 2 分钟 interval 所以你必须使用负值，-1200000000.

可能的真实意图是让它在时钟的特定时间醒来，给定使用场景，使用DateTime.ToUniversalTime().ToFileTime()

WaitForSingleObject 立即发出信号

WaitForSingleObject signalled immediately

c#

wakeup

winforms

sleep-mode