c# - 简单线程，为什么会这样？ (C# 窗体)

Question

我目前正在探索 C# WinForms 中的线程实现，我创建了这个简单的应用程序:

我只是想知道为什么这个应用程序的内存使用量在我启动、停止、启动和再次停止应用程序后不断增长。我在想，当我按下停止按钮时，我的线程实例并没有真正终止或中止。请在下面考虑我的代码，我们将不胜感激任何帮助或建议。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;

namespace ThreadingTest
{
    public partial class Form1 : Form
    {
        private delegate void TickerDelegate(string s);
        bool stopThread = false;
        TickerDelegate tickerDelegate1;
        Thread thread1;

        public Form1()
        {
            InitializeComponent();
            tickerDelegate1 = new TickerDelegate(SetLeftTicker);
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            thread1 = new Thread(new ThreadStart(disp));
            thread1.Start();
        }

        void disp()
        {
            while (stopThread == false)
            {
                listBox1.Invoke(tickerDelegate1, new object[] { DateTime.Now.ToString() });
                Thread.Sleep(1000);
            }
        }

        private void SetLeftTicker(string s)
        {
            listBox1.Items.Add(s);
        }

        private void btnStop_Click(object sender, EventArgs e)
        {
            stopThread = true;
            if (thread1.IsAlive)
            {
                thread1.Abort();
            }
        }

        private void btnStart_Click(object sender, EventArgs e)
        {
            stopThread = false;
            thread1 = new Thread(new ThreadStart(disp));
            thread1.Start();
        }

        private void btnCheck_Click(object sender, EventArgs e)
        {
            if (thread1.IsAlive)
            {
                MessageBox.Show("Is Alive!");
            }
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            listBox1.Items.Clear();
        }
    }
}

Answer 1

OK，有几个建议:

使用可变标志

使您的标志可变...如果您不这样做，则线程可能永远不会看到对标志的更新。

volatile bool stopThread = false;

设置为背景

将 IsBackground 属性设置为 true:如果应用程序退出，它会强制终止线程，否则您可能会得到一个即使在应用程序关闭后仍然存在的“幽灵线程”。

thread1.IsBackground = true;
thread1.Start();

如果线程刚刚开始休眠，那么你甚至会在它有机会读取标志之前中止它......此外你不想使用 Abort 因为:

...if one thread calls Abort on another thread, the abort interrupts whatever code is running. There is a chance the thread could abort while a finally block is running, in which case the finally block is aborted. There is also a chance that a static constructor could be aborted. In rare cases, this might prevent instances of that class from being created in that application domain.

使用中断代替中止

因此，我建议您调用 Interrupt 并在线程内处理异常，而不是使用 abort:

private void btnStop_Click(object sender, EventArgs e)
{
    // have another method for re-use
    StopThread();
}

private void StopThread()
{
    stopThread = true;

    // the time out is 100 ms longer than the thread sleep
    thread1.Join(1100);

    // if the thread is still alive, then interrupt it
    if(thread1.IsAlive)
    {
        thread1.Interrupt();
    }
}

不要“泄漏”线程

每次单击“开始”按钮时都会泄漏线程...如果 thread1 已经分配了一个线程并且您为它分配了另一个线程，那么前一个一个将继续存在。在开始另一个线程之前，您需要停止上一个线程。

private void btnStart_Click(object sender, EventArgs e)
{
    // stop the previous thread
    StopThread();

    // create a new thread
    stopThread = false;
    thread1 = new Thread(new ThreadStart(disp));
    thread1.IsBackground = true;// set it to background again
    thread1.Start();
}

处理中断

最后，您需要处理线程中的中断:

void disp()
{
    try
    {
        while (stopThread == false)
        {
            listBox1.Invoke(tickerDelegate1, new object[] { DateTime.Now.ToString() });
            Thread.Sleep(1000);
        }
    }
    catch(ThreadInterruptedException)
    {
        // ignore the exception since the thread should terminate
    }
}

我想就是这样了......哦......实际上，还有一件事:小心线程! ;)