求助怎样终止一个事件？

Question

当按下 某个键 后触发一个事件，触发后开始一个循环，当再次按下 任意键 后停止。该如何实现？

Answer 1

不好意思，看来是我没说明白，重新说下：
比如有一个 textbox1 控件，当按下回车 时，触发它的 KeyPress 事件，开始执行一个循环，当再次按下键盘的任意键时，结束这个循环。试了很多办法都不行，现在需要解决的问题就是怎样在循环体内检查键盘是否有按下？

Answer 2

这就是典型的在循环体内嵌入goto语句的要求

Answer 3

申明一个bool类型的全局变量canRun=true; 捕获键盘按下事件时把canRun=false,在循环中判断是否canRun就好了

Answer 4

浅层次代码,随意写的：
bool _a=true;
线程 _thread=null;
点击事件(...)
{
    if(thread==null)
    {
       thread=.....(匿名方法);
    }
    if(a)
    {
       thread.start();
    }
    else
    {
       thread.sleep();
    }
    a=!a;
}

Answer 5

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 KeyPressTwice
{
    /// <summary>
    ///  由于子线程不能修改UI界面上空间信息，
    ///  To remedy this, you will have to use a dispatcher as descibed in the MSDN article:
    ///  <a pref="http://msdn.microsoft.com/en-us/library/ms171728.aspx">How to: Make Thread-Safe Calls to Windows Forms Controls</a>
    /// </summary>
    public partial class Form1 : Form
    {
        private bool canRun = false;
        private Thread thread;
        delegate void SetTextCallback(string text);
        public Form1()
        {
            InitializeComponent();
            thread = new Thread(ShowCounter);
        }        public void ShowCounter()
        {
            int counter = 0;
            while (true)
            {
                SetText((counter++).ToString());
                Thread.Sleep(1000);
            }
        }        private void SetText(string text)
        {
            if (this.textBox1.InvokeRequired)
            {
                SetTextCallback backCall = new SetTextCallback(SetText);
                this.Invoke(backCall, new Object[] { text });
            }
            else
            {
                this.textBox1.Text = text;
            }
        }        private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            switch(Char.ToLower(e.KeyChar))
            {
                case 's':
                    if (thread.ThreadState == ThreadState.Unstarted) 
                    {
                        thread.Start();
                    }
                    else if (thread.ThreadState == ThreadState.Aborted)
                    {
                        thread = new Thread(ShowCounter);
                        thread.Start();
                    }
                    break;
                case 'f':
                    e.Handled = true;
                    thread.Abort();
                    break;
                default:
                    break;
            }
            
        }        private void justCycle()
        {
            int i = 0;
            while (true)
            {
                textBox1.Text = Convert.ToString(i++);
                if (canRun) 
                {
                    break;
                }
            }
        }
    }
}
希望解决了你的问题

Answer 6

如果，只需要在某些Form中消除Cross-thread InvalidOperationException建议，可以在Form.cs在代码初始化中，将Control.CheckForIllegalCrossThreadCalls = false; 可以完成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 KeyPressTwice
{
    /// <summary>
    ///  由于子线程不能修改UI界面上空间信息，
    ///  To remedy this, you will have to use a dispatcher as descibed in the MSDN article:
    ///  <a pref="http://msdn.microsoft.com/en-us/library/ms171728.aspx">How to: Make Thread-Safe Calls to Windows Forms Controls</a>
    /// </summary>
    public partial class Form1 : Form
    {
        private bool canRun = false;
        private Thread thread;
        delegate void SetTextCallback(string text);
        public Form1()
        {
            InitializeComponent();
            thread = new Thread(ShowCounter);
            Control.CheckForIllegalCrossThreadCalls = false;
        }        public void ShowCounter()
        {
            int counter = 0;
            while (true)
            {
                SetText((counter++).ToString());
                Thread.Sleep(1000);
            }
        }        private void SetText(string text)
        {
            //if (this.textBox1.InvokeRequired)
            //{
            //    SetTextCallback backCall = new SetTextCallback(SetText);
            //    this.Invoke(backCall, new Object[] { text });
            //}
            //else
            {
                this.textBox1.Text = text;
            }
        }        private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            switch(Char.ToLower(e.KeyChar))
            {
                case 's':
                    if (thread.ThreadState == ThreadState.Unstarted) 
                    {
                        thread.Start();
                    }
                    else if (thread.ThreadState == ThreadState.Aborted)
                    {
                        thread = new Thread(ShowCounter);
                        thread.Start();
                    }
                    break;
                case 'f':
                    e.Handled = true;
                    thread.Abort();
                    break;
                default:
                    break;
            }
            
        }    }
}