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","","CXY");

             for (int i = ; i <= ; 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();
                 }
             }
         }

         //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(, );
             this.btnStart.Name = "btnStart";
             this.btnStart.Size = new System.Drawing.Size(, );
             this.btnStart.TabIndex = ;
             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(, );
             this.btnCancel.Name = "btnCancel";
             this.btnCancel.Size = new System.Drawing.Size(, );
             this.btnCancel.TabIndex = ;
             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(, );
             this.label1.Name = "label1";
             this.label1.Size = new System.Drawing.Size(, );
             this.label1.TabIndex = ;
             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(, );
             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;
     }
 }