Unity3d热更新（三）：更新资源流程

1.生成配置文件

在资源打包AssetBundle后，需要计算资源文件的MD5值，生成配置文件。下面给出一个例子：

 // 获取Res文件夹下所有文件的相对路径和MD5值
 string[] files = Directory.GetFiles(resPath, "*", SearchOption.AllDirectories);
 StringBuilder versions = new StringBuilder();
 for (int i = 0, len = files.Length; i < len; i++)
 {
     string filePath = files[i];
     string extension = filePath.Substring(files[i].LastIndexOf("."));
     if (extension == ".unity3d")
     {
         string relativePath = filePath.Replace(resPath, "").Replace("\\", "/");
         string md5 = MD5File(filePath);
         versions.Append(relativePath).Append(",").Append(md5).Append("\n");
     }
 }
 // 生成配置文件
 FileStream stream = new FileStream(resPath + "version.txt", FileMode.Create);
 byte[] data = Encoding.UTF8.GetBytes(versions.ToString());
 stream.Write(data, 0, data.Length);
 stream.Flush();
 stream.Close();

其中生成MD5值的方法如下：

 public static string MD5File(string file)
 {
     try
     {
         FileStream fs = new FileStream(file, FileMode.Open);
         System.Security.Cryptography.MD5 md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
         byte[] retVal = md5.ComputeHash(fs);
         fs.Close();
         StringBuilder sb = new StringBuilder();
         for (int i = 0; i < retVal.Length; i++)
         {
             sb.Append(retVal[i].ToString("x2"));
         }
         return sb.ToString();
     }
     catch (Exception ex)
     {
         throw new Exception("md5file() fail, error:" + ex.Message);
     }
 }

2.版本比较

先加载本地的version.txt，将结果缓存起来。下载服务器的version.txt，与本地的version进行比较，筛选出需要更新和新增的资源。

3.下载资源

依次下载更新的资源，如果本地已经有旧资源，则替换之，否则就新建保存起来。

4.更新本地版本配置文件version.txt

用服务器的version.txt替换掉本地的version.txt。这样做是为了确保下次启动的时候，不会再重复更新了。

关于上述的流程，下面有个小例子。这里没有用到web服务器，而是将本地的另外一个文件夹作为资源服务器目录。这里的目录只针对windows下的版本进行测试。如果要在手机平台上，需要记得更新相关的路径。

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 using System.Text;
 using System.IO;

 public class ResUpdate : MonoBehaviour
 {
     public static readonly string VERSION_FILE = "version.txt";
     public static readonly string LOCAL_RES_URL = "file://" + Application.dataPath + "/Res/";
     public static readonly string SERVER_RES_URL = "file:///C:/Res/";
     public static readonly string LOCAL_RES_PATH = Application.dataPath + "/Res/";

     private Dictionary LocalResVersion;
     private Dictionary ServerResVersion;
     private List NeedDownFiles;
     private bool NeedUpdateLocalVersionFile = false;

     void Start()
     {
         //初始化
         LocalResVersion = new Dictionary();
         ServerResVersion = new Dictionary();
         NeedDownFiles = new List();

         //加载本地version配置
         StartCoroutine(DownLoad(LOCAL_RES_URL + VERSION_FILE, delegate(WWW localVersion)
         {
             //保存本地的version
             ParseVersionFile(localVersion.text, LocalResVersion);
             //加载服务端version配置
             StartCoroutine(this.DownLoad(SERVER_RES_URL + VERSION_FILE, delegate(WWW serverVersion)
             {
                 //保存服务端version
                 ParseVersionFile(serverVersion.text, ServerResVersion);
                 //计算出需要重新加载的资源
                 CompareVersion();
                 //加载需要更新的资源
                 DownLoadRes();
             }));

         }));
     }

     //依次加载需要更新的资源
     private void DownLoadRes()
     {
         if (NeedDownFiles.Count == 0)
         {
             UpdateLocalVersionFile();
             return;
         }

         string file = NeedDownFiles[0];
         NeedDownFiles.RemoveAt(0);

         StartCoroutine(this.DownLoad(SERVER_RES_URL + file, delegate(WWW w)
         {
             //将下载的资源替换本地就的资源
             ReplaceLocalRes(file, w.bytes);
             DownLoadRes();
         }));
     }

     private void ReplaceLocalRes(string fileName, byte[] data)
     {
         string filePath = LOCAL_RES_PATH + fileName;
         FileStream stream = new FileStream(LOCAL_RES_PATH + fileName, FileMode.Create);
         stream.Write(data, 0, data.Length);
         stream.Flush();
         stream.Close();
     }

     //显示资源
     private IEnumerator Show()
     {
         WWW asset = new WWW(LOCAL_RES_URL + "cube.assetbundle");
         yield return asset;
         AssetBundle bundle = asset.assetBundle;
         Instantiate(bundle.Load("Cube"));
         bundle.Unload(false);
     }

     //更新本地的version配置
     private void UpdateLocalVersionFile()
     {
         if (NeedUpdateLocalVersionFile)
         {
             StringBuilder versions = new StringBuilder();
             foreach (var item in ServerResVersion)
             {
                 versions.Append(item.Key).Append(",").Append(item.Value).Append("\n");
             }

             FileStream stream = new FileStream(LOCAL_RES_PATH + VERSION_FILE, FileMode.Create);
             byte[] data = Encoding.UTF8.GetBytes(versions.ToString());
             stream.Write(data, 0, data.Length);
             stream.Flush();
             stream.Close();
         }
         //加载显示对象
         StartCoroutine(Show());
     }

     private void CompareVersion()
     {
         foreach (var version in ServerResVersion)
         {
             string fileName = version.Key;
             string serverMd5 = version.Value;
             //新增的资源
             if (!LocalResVersion.ContainsKey(fileName))
             {
                 NeedDownFiles.Add(fileName);
             }
             else
             {
                 //需要替换的资源
                 string localMd5;
                 LocalResVersion.TryGetValue(fileName, out localMd5);
                 if (!serverMd5.Equals(localMd5))
                 {
                     NeedDownFiles.Add(fileName);
                 }
             }
         }
         //本次有更新，同时更新本地的version.txt
         NeedUpdateLocalVersionFile = NeedDownFiles.Count > 0;
     }

     private void ParseVersionFile(string content, Dictionary dict)
     {
         if (content == null || content.Length == 0)
         {
             return;
         }
         string[] items = content.Split(new char[] { '\n' });
         foreach (string item in items)
         {
             string[] info = item.Split(new char[] { ',' });
             if (info != null && info.Length == 2)
             {
                 dict.Add(info[0], info[1]);
             }
         }

     }

     private IEnumerator DownLoad(string url, HandleFinishDownload finishFun)
     {
         WWW www = new WWW(url);
         yield return www;
         if (finishFun != null)
         {
             finishFun(www);
         }
         www.Dispose();
     }

     public delegate void HandleFinishDownload(WWW www);
 }