线程暂停

如何暂停一个线程

实现一个需求，在上位机项目中执行一直都PLC数据和将PLC数据写入数据的操作。当按下按钮时暂停读写操作

原理：开两个线程，每个线程执行一个死循环，在循环体内一直读PLC数据和写入数据库操作

 

方法一：通过控制flag来控制线程的暂停

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

namespace LoadDataByTask
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.button2.Text = "暂停";
        }
        bool falg = true;//控制位
        ManualResetEvent mark = new ManualResetEvent(true);
        private void button1_Click(object sender, EventArgs e)
        {
            falg = true;
            //执行读PLC数据任务
            Task.Run(() =>
            {
                while (true)
                {
                    //第一种方法

                    for (int i = 0; i < 10; i++)
                    {
                        if (falg)
                        {
                            Console.WriteLine("read data from plc" + i + ":" + System.DateTime.Now.ToString());
                            Thread.Sleep(200);
                        }
                    }                    
                }
            });
            //执行将数据写入数据库任务
            Task.Run(() =>
            {
                while (true)
                {
                    //第一种方法

                    for (int i = 0; i < 10; i++)
                    {
                        if (falg)
                        {
                            Console.WriteLine("write data " + i + ":" + System.DateTime.Now.ToString());
                            Thread.Sleep(200);
                        }
                    }                   
                }
            });
        }

        private void button2_Click(object sender, EventArgs e)
        {            
            falg = false;
        }
    }
}

 

方法一的缺点：

线程并不是真正的暂停，线程暂停后再启动CPU占用率很高，如下

 

 

 

---

方法2：使用ManualResetEvent进行控制线程的暂停

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

namespace LoadDataByTask
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.button2.Text = "暂停";
        }
        
        ManualResetEvent mark = new ManualResetEvent(true);
        private void button1_Click(object sender, EventArgs e)
        {
            falg = true;
            //执行读PLC数据任务
            Task.Run(() =>
            {
                while (true)
                {            
                    //第二种方法                    
                    for (int i = 0; i < 100; i++)
                    {
                        int k = i;
                        mark.WaitOne();
                        //Console.WriteLine("read data from plc" + k + ":" + System.DateTime.Now.ToString());
                        Console.WriteLine("read data from plc" + k + "当前线程：" + Thread.CurrentThread.ManagedThreadId.ToString());
                        Thread.Sleep(1000);
                    }
                }
            });

            //执行将数据写入数据库任务
            Task.Run(() =>
            {
                while (true)
                {                    
                    //第二种方法
                    mark.WaitOne();
                    for (int i = 0; i < 100; i++)
                    {
                        int k = i;
                        mark.WaitOne();
                        //Console.WriteLine("write data " + k + ":" + System.DateTime.Now.ToString());
                        Console.WriteLine("write data " + k + "@" + "当前线程：" + Thread.CurrentThread.ManagedThreadId.ToString());
                        Thread.Sleep(1000);
                    }
                }
            });
        }

        private void button2_Click(object sender, EventArgs e)
        {
            if (this.button2.Text == "暂停")
            {
                mark.Reset();
                this.button2.Text = "恢复";
            }
            else
            {
                mark.Set();
                this.button2.Text = "暂停";
            }            
        }
    }
}

第二种线程暂停的方案为最佳方案，线程暂停的时候不会引起CPU占用率的增加。

---

 

例子：使用ManualResetEvent进行控制线程暂停的另一个例子

引用：【C#】怎样做线程的[暂停/继续]操作_哔哩哔哩_bilibili，感谢UP糖君哒

实现一个PrograssBar的暂停，效果入下：

 

 

 

 代码如下：

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

namespace PausePrograssBar
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.Load += Form1_Load;
            this.btnControl.Text = "暂停";
            this.FormClosed += Form1_FormClosed;
        }

        private void Form1_FormClosed(object sender, FormClosedEventArgs e)
        {
            System.Environment.Exit(0);
        }

        ManualResetEvent mark = new ManualResetEvent(true);
        private void Form1_Load(object sender, EventArgs e)
        {
            Task.Run(() =>
            {
                while (this.progressBar1.Value < 100)
                {
                    mark.WaitOne();
                    Thread.Sleep(200);
                    this.Invoke(new Action(() => { this.progressBar1.Value++; }));
                }
            });
        }

        private void btnControl_Click(object sender, EventArgs e)
        {
            if (this.btnControl.Text == "暂停")
            {
                mark.Reset();
                this.btnControl.Text = "继续";
            }
            else
            {
                mark.Set();
                this.btnControl.Text = "暂停";
            }
        }
    }
}