Question

C#多线程预期结果，按下按钮时两个线程交替执行； 实际结果，task1强制执行完释放后才执行task2。

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 WindowsFormsApplication1
{
public partial class Form1 : Form
{
int test1 = 0;
Thread Ttask1 = null;
public Form1()
{
InitializeComponent();
Thread Ttask2 = new Thread(new ThreadStart(tttask2));
Ttask2.IsBackground = true;
Ttask2.Start();
}
private delegate void TASK_DELT();
private void task2()
{
if (test1++ % 2 == 0)
{
pictureBox1.BackColor = Color.Blue;
}
else
{
pictureBox1.BackColor = Color.Red;
}
textBox1.Clear();
textBox1.Text = test1.ToString();
textBox1.Refresh();
}
private void tttask2()
{
while (true)
{
Thread.Sleep(250);
//如果是跨线程调用
if (InvokeRequired)
{
this.textBox1.BeginInvoke(new TASK_DELT(task2));
}
else
{
task2();
}
}
}
private void delays(int t)
{
for (int i = 0; i < t; i++)
{
textBox1.Clear();
textBox1.Text = i.ToString();
textBox1.Refresh();
Thread.Sleep(1);
for (int j = 0; j < 0x08f00000; j++) ;
}
pictureBox2.BackColor = Color.Green;
}
private delegate void TASKPRA_DELT(int i);
private void task1()
{
//如果是跨线程调用
if (InvokeRequired)
{
this.textBox1.Invoke(new TASKPRA_DELT(delays), 10);
}
else
{
delays(10);
}

}
private void button1_Click(object sender, EventArgs e)
{
pictureBox2.BackColor = Color.Transparent;
Ttask1 = new Thread(new ThreadStart(task1));
Ttask1.IsBackground = true;
Ttask1.Start();
}
}
}
请问怎么保证两个线程交替执行？

Answer 1

问题在于，你没有理解Control.Invoke这个方法的机制。

for (int j = 0; j < 0x08f00000; j++) ;

你这里是非常耗时间的。但执行这段代码的线程，不是Ttask1，而是当前的UI线程。

task2方法，也不是由Ttask2调用。也是在当前的UI线程执行。

所以在执行delays时，task2会处于等待状态。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading;
using System.Windows.Forms;
 
namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        int test1 = 0;
        Thread Ttask1 = null;
        public Form1()
        {
            InitializeComponent();
            Thread Ttask2 = new Thread(new ThreadStart(tttask2));
            Ttask2.IsBackground = true;
            Ttask2.Start();
        }
        private delegate void TASK_DELT();
        private void task2()
        {
            if (test1++ % 2 == 0)
            {
                Action func1 = delegate {
                    pictureBox1.BackColor = Color.Blue;
                };
                this.pictureBox1.Invoke(func1);
            }
            else
            {
                Action func2 = delegate {
                    pictureBox1.BackColor = Color.Red;
                };
                this.pictureBox1.Invoke(func2);
            }
 
            Action func3 = delegate {
                textBox1.Clear();
                textBox1.Text = test1.ToString();
                textBox1.Refresh();
            };
            this.textBox1.Invoke(func3);
        }
        private void tttask2()
        {
            while (true)
            {
                Thread.Sleep(250);
                //如果是跨线程调用 
                //if (InvokeRequired)
                //{
                //    this.textBox1.BeginInvoke(new TASK_DELT(task2));
                //}
                //else
                {
                    task2();
                }
            }
        }
        private void delays(int t)
        {
            for (int i = 0; i < t; i++)
            {
                Action func1 = delegate {
                    textBox1.Clear();
                    textBox1.Text = i.ToString();
                    textBox1.Refresh();
                };
                this.textBox1.Invoke(func1);
 
                Thread.Sleep(1);
                for (int j = 0; j < 0x08f00000; j++) ;
            }
 
            Action func2 = delegate {
                pictureBox2.BackColor = Color.Green;
            };
            this.pictureBox2.Invoke(func2);
        }
        private delegate void TASKPRA_DELT(int i);
        private void task1()
        {
            //如果是跨线程调用 
            //if (InvokeRequired)
            //{
            //    this.textBox1.Invoke(new TASKPRA_DELT(delays), 10);
            //}
            //else
            {
                delays(10);
            }
 
        }
        private void button1_Click(object sender, EventArgs e)
        {
            pictureBox2.BackColor = Color.Transparent;
            Ttask1 = new Thread(new ThreadStart(task1));
            Ttask1.IsBackground = true;
            Ttask1.Start();
        }
    }
}

Answer 2

用InInvoke不用BeginInvoke

追问

您好，已经试过Invoke，同样是不行。task1()
还是强行执行完才给task2()
。并未交替执行。

追答

方便把程序传上来吗