多线程实现资源下载

using UnityEngine;
using System.Collections;
using System.Threading;
using System.IO;
using System.Net;
public class ThreadDownLoadFile  {

    //下载地址
    public string url;

    //下载到本地的存入的位置
    public string localPath;
    //检查是否下载完成
    public bool isDone = false;

    public ThreadDownLoadFile(string url,string localPath)
    {
        this.url = url;
        this.localPath = localPath;

    }



    //线程工作方法--下载文件
    public void DownFile()
    {
        long lastDownPos = 0;
        //检查本地是否    已经有该文件，如果有，则续传
        FileStream fs = null;
        if (File.Exists(localPath))
        {
            fs = File.Open(localPath, FileMode.Append);
            lastDownPos = fs.Length;
        }
        else //如果没有，新建
        {
            fs = File.Create(localPath);
        }

        //开始一个线程
        //web请求的处理
        HttpWebRequest request = HttpWebRequest.Create(url) as HttpWebRequest;
        //是否断点续传
        if (lastDownPos > 0)
        {
            request.AddRange((int)lastDownPos);//从上次下载的位置开始 读取数据
                                               //从请求对象得到响应对象。从响应对象取得响应数据
            using (Stream stream = request.GetResponse().GetResponseStream())
            {
                int nReadSize = 0;
                do
                {
                    byte[] buffer = new byte[1024 * 100];
                    nReadSize = stream.Read(buffer, 0, buffer.Length);
                    fs.Write(buffer, 0, nReadSize);
                } while (nReadSize > 0);
            }
            fs.Flush();
            fs.Close();
            isDone = true;
        }
    }

}

using UnityEngine;
using System.Collections;
using System.IO;
using System.Threading;

public class Test : MonoBehaviour {

    ThreadDownLoadFile downFile = null;
    // Use this for initialization
    public void OnGUI()
    {
        if (GUILayout.Button("Down"))
        {
            //开启线程，开始下载
            string url = "http://www.rongweijun.cn";

          string localPath=  Application.persistentDataPath + "/" + Path.GetFileName(url);
            downFile = new ThreadDownLoadFile(url, localPath);

            Thread thread = new Thread(downFile.DownFile);
            thread.Start();
        }
        if( downFile!=null && downFile.isDone)
        {
            GUILayout.Label("OK");
        }
    }
}