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本文诞生于乐元素面试过程，被面试官问到AssetBundle多线程异步下载时，愣了半天，同样也被深深的鄙视一回（做了3年多u3d 这个都没用过），所以发誓要实现出来填补一下自己的空白，同时分享给大家。说明：本人只在pc和Android下测试好使，其他平台未知！
直接贴代码，都是C# http的API，不懂得自己百科。
using UnityEngine; using System.Collections; using System; using System.Text; using System.Net; using System.IO;internal class WebReqState {public byte[] Buffer;public FileStream fs;public const int BufferSize = 1024;public Stream OrginalStream;public HttpWebResponse WebResponse;public WebReqState(string path){Buffer = new byte[1024];fs = new FileStream(path,FileMode.Create);}}public class HttpHelper {string path = null;string assetName;public HttpHelper(string path){this.path = path;}public void AsyDownLoad(string url) {Debug.Log(url);assetName = url.Split('/')[4];Debug.Log(assetName);HttpWebRequest httpRequest = WebRequest.Create(url) as HttpWebRequest;httpRequest.BeginGetResponse( new AsyncCallback(ResponseCallback), httpRequest); }void ResponseCallback(IAsyncResult ar) {HttpWebRequest req = ar.AsyncState as HttpWebRequest;if(req == null) return;HttpWebResponse response = req.EndGetResponse(ar) as HttpWebResponse;if(response.StatusCode != HttpStatusCode.OK){response.Close();return;}Debug.Log(path+ "/"+assetName);WebReqState st = new WebReqState(path+ "/"+assetName);st.WebResponse = response;Stream responseStream = response.GetResponseStream();st.OrginalStream = responseStream;responseStream.BeginRead(st.Buffer,0,WebReqState.BufferSize,new AsyncCallback(ReadDataCallback),st); }void ReadDataCallback(IAsyncResult ar) {WebReqState rs = ar.AsyncState as WebReqState;int read =rs.OrginalStream.EndRead(ar);if(read>0){rs.fs.Write(rs.Buffer,0,read);rs.fs.Flush();rs.OrginalStream.BeginRead(rs.Buffer, 0, WebReqState.BufferSize, new AsyncCallback(ReadDataCallback), rs);}else{rs.fs.Close();rs.OrginalStream.Close();rs.WebResponse.Close();Debug.Log(assetName+":::: success");} } }
下载部分：
if(GUI.Button(new Rect(0,0,100,30),"test")) {string rootPath = Application.persistentDataPath;//android上保存到 /storage/sdcard0/Android/data/包名(例如：com.example.test)/filesfor(int i =0;i<str.Length;i++) //str是string型数组，存放部分assetbundle名字 {Thread thread = new Thread(new ParameterizedThreadStart(DownAsset)); //ParameterizedThreadStart 多线程传参 thread.Start(rootPath+"|"+str[i]); //只能带一个object参数 所以使用字符串拼接 } } void DownAsset(System.Object file) {string[] fileName = file.ToString().Split('|');HttpHelper help = new HttpHelper(fileName[0]);help.AsyDownLoad("http://192.168.0.103/unity/"+fileName[1]+".AssetBundle");//注意在手机上测试 该对Ip地址 }
下载完成后 可以去/storage/sdcard0/Android/data/包名(例如：com.example.test)/files查找对应文件
加载部分：
if(GUI.Button(new Rect(0,30,100,30),"load")) {for(int i =0;i<str.Length;i++){StartCoroutine(LoadAsset(str[i],i));} } IEnumerator LoadAsset(string name,int i) {WWW w = new WWW("file://"+Application.persistentDataPath+"/"+name+".AssetBundle");yield return w;Instantiate(w.assetBundle.mainAsset,new Vector3(i*2,0,0),Quaternion.identity);w.assetBundle.Unload(false); }
注意事项：
1、pc测试 需要修改IP地址，本地测试改为127.0.0.1 同时Application.persistentDataPath最好做修改，因为在pc上Application.persistentDataPath：C:\Users\用户名\AppData\LocalLow\DefaultCompany\u3d工程名，可以下载到此文件夹下，但是加载的时候会报错，没什么权限之类的
2、android上需要stripping level设置为Disabled
