BackgroundWorker的简单用法

微软的官方例子

BackgroudWorker就是一个封装好的异步处理类(就是多线程，广泛用于winform开发中)

例子：

1.界面效果：

    一个label，两个button

  

2.Form2.cs的代码

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;

namespace BackgroundWorkerTest
{
    public partial class Form2 : Form
    {
        /*
         * 使用BackgroundWorker的用法很多
         * 1.可以直接从左边控件列表中拖一个到界面中
         * 2.动态写代码生成，这里我是把它作为成员变量了
         * **/
        private BackgroundWorker _worker = new BackgroundWorker();

        public Form2()
        {
            InitializeComponent();

            //设置是否允许报告进度
            _worker.WorkerReportsProgress = true;
            //设置是否允许取消
            _worker.WorkerSupportsCancellation = true;


            //BackgroundWorker的三个事件之一，异步处理是所要执行的动作
            _worker.DoWork += new DoWorkEventHandler(_worker_DoWork);

            //BackgroundWorker的三个事件之二，当进度改变时所要执行的动作
            _worker.ProgressChanged += new ProgressChangedEventHandler(_worker_ProgressChanged);

            //BackgroundWorker的三个事件之三，当任务正常完成或手动取消时，所要执行的动作
            _worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(_worker_RunWorkerCompleted);
        }


        //运行RunWorkerAsync()时就出发此方法，而且此方法不能与UI有交互，会抛异常
        void _worker_DoWork(object sender, DoWorkEventArgs e)
        {
            //这个类是用来测试报告进度时，除了可以报告进度外，还可以返回一个object的变量
            Person tommy = new Person("Tommy.Huang","25","CXY");

            for (int i = 1; i <= 100; i++)
            {
                //如果想要实现能够中途取消的功能，就必须在DoWork里面判断是否点击了取消
                //CancellationPending用于判断是运行了CancelAsync()方法
                if (_worker.CancellationPending)
                {
                    e.Cancel = true;
                    break;
                }
                else
                {
                    _worker.ReportProgress(i,tommy);//ReportProgress可以带1个或2个参数，第一个为进度int，第二个为object
                    //因为太快，看不到效果，所以让线程每一次暂停半秒
                    System.Threading.Thread.Sleep(100);
                }
            }
        }

        //当进度有所改变时，就会触发该方法，此方法可以与UI交互，所以通常在此方法中处理
        void _worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            Person p = e.UserState as Person;
            this.label1.Text = e.ProgressPercentage.ToString()+"% -"+p.Name;
        }

        //当异步线程正常运行结束，或者点击取消时都会执行此方法
        void _worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Cancelled)
                System.Windows.Forms.MessageBox.Show("取消了");
            else
                System.Windows.Forms.MessageBox.Show("完成了！");
        }

        private void btnStart_Click(object sender, EventArgs e)
        {
            //需要先判断backgroundWorker是否正在运行
            if (!_worker.IsBusy)
            {
                //RunWorkerAsync()启动线程
                _worker.RunWorkerAsync();
            }
        }

        private void btnCancel_Click(object sender, EventArgs e)
        {
            //先判断backgroundWorker是否支持取消
            if (_worker.WorkerSupportsCancellation)
            {
                //CancelAsync()取消线程
                _worker.CancelAsync();
            }
        }

    }
}

3.控件代码：Form2.Designer.cs

namespace BackgroundWorkerTest
{
    partial class Form2
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.btnStart = new System.Windows.Forms.Button();
            this.btnCancel = new System.Windows.Forms.Button();
            this.label1 = new System.Windows.Forms.Label();
            this.SuspendLayout();
            // 
            // btnStart
            // 
            this.btnStart.Location = new System.Drawing.Point(42, 165);
            this.btnStart.Name = "btnStart";
            this.btnStart.Size = new System.Drawing.Size(75, 23);
            this.btnStart.TabIndex = 0;
            this.btnStart.Text = "开始";
            this.btnStart.UseVisualStyleBackColor = true;
            this.btnStart.Click += new System.EventHandler(this.btnStart_Click);
            // 
            // btnCancel
            // 
            this.btnCancel.Location = new System.Drawing.Point(249, 165);
            this.btnCancel.Name = "btnCancel";
            this.btnCancel.Size = new System.Drawing.Size(75, 23);
            this.btnCancel.TabIndex = 1;
            this.btnCancel.Text = "取消";
            this.btnCancel.UseVisualStyleBackColor = true;
            this.btnCancel.Click += new System.EventHandler(this.btnCancel_Click);
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Location = new System.Drawing.Point(61, 47);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(35, 13);
            this.label1.TabIndex = 2;
            this.label1.Text = "label1";
            // 
            // Form2
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(388, 230);
            this.Controls.Add(this.label1);
            this.Controls.Add(this.btnCancel);
            this.Controls.Add(this.btnStart);
            this.Name = "Form2";
            this.Text = "Form2";
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.Button btnStart;
        private System.Windows.Forms.Button btnCancel;
        private System.Windows.Forms.Label label1;
    }
}