为什么System.Threading.Timer自行停止？ [英] Why does System.Threading.Timer stop on its own?

问题描述

我在做一个小测试项目之前，我在一个Windows服务项目中使用 System.Threading.Timer 。它的工作奇妙，但计时器一两分钟后自行停止

I'm doing a small test project before I use System.Threading.Timer in a Windows Service project. It's working wonderfully, however the timer stops on its own after a minute or two.

的全部源代码的测试项目为：

The full source for the test project is:

using System;
using System.Windows.Forms;
using System.Threading;

namespace studyTimers {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e) {
            TimerCallback timerDelegate = new TimerCallback(tick);
            System.Threading.Timer testTimer = new System.Threading.Timer(timerDelegate, null, 1000, 1000);
        }

        void tick(Object obj) {
            if (label1.InvokeRequired) {
                label1.Invoke(new MethodInvoker(() => tick(obj)));
            } else {
                label1.Text = DateTime.Now.ToString();
            }
        }
    }
}

的

目标显然是要更新与当前时间的标签。我注意到，更新了一下后停止。为什么会这样呢？

The goal is obviously to update a label with the current time. I am noticing that updating stops after a bit. Why would this be?

推荐答案

如果你需要一个Windows窗体上的计时器跌得系统。 Windows.Forms.Timer 到窗体 - 没有理由使用 System.Threading.Timer 除非你需要比55毫秒更好的分辨率

If you need a timer on a Windows Form then drop a System.Windows.Forms.Timer onto the form - there's no reason to use a System.Threading.Timer unless you need better resolution than 55 ms.

计时器停止的原因是因为它被垃圾收集。你允许它走出去的范围在 Form1_Load的方法，因为你只把它声明为一个局部变量。为了保持计时器活着，它需要在表单类，以便GC知道它仍然需要

The reason the timer "stops" is because it's being garbage-collected. You're allowing it to go out of scope in the Form1_Load method because you only declare it as a local variable. In order to keep the timer "alive", it needs to be a private field on the form class so that the GC knows it's still needed.

在换句话说一个私有字段：

In other words:

public partial class Form1 : Form
{
    private System.Threading.Timer testTimer;

    ...

    public void Form1_Load(object sender, EventArgs e)
    {
        TimerCallback timerDelegate = new TimerCallback(tick);
        testTimer = new System.Threading.Timer(timerDelegate, null, 1000, 1000);
    }
}

但同样，在这种情况下，它simplier使用 System.Windows.Forms.Timer ，这是在说你可以拖放到窗体工具箱中的实际组成部分。

But again, in this case it's simplier to use System.Windows.Forms.Timer, which is an actual component in the toolbox that you can just drop onto the form.

的修改的 - 正如现在的注释透露，如果这仅仅是一个测试应用程序和实际应用是一个Windows服务，您的不可以的使用 System.Windows.Forms.Timer 为。只要记住，不要让你的 System.Threading.Timer 走出去的范围。

Edit - As the comments now reveal, if this is just a test app and the real application is in a Windows Service, you cannot use System.Windows.Forms.Timer for that. Just remember not to let your System.Threading.Timer go out of scope.

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