前言
此文章适合不太了解资源加载的萌新，有了入门基础之后再去github上搜大牛写的专业的资源加载方案才能得心应手，不然的话会看的很吃力或者说一脸懵逼。Unity里面关于资源加载我们都知道是下载更新AssetBundle，关于AssetBundle我之前的文章已经详细介绍过，没看过的朋友可以在看一下。下面介绍的资源加载的Demo有以下几点：
1.WWW下载图片资源
2.HTTP下载apk文件，并且支持断点续传，并且显示加载进度条
3.HTTP多线程下载文件
部分核心代码和讲解
WWW下载
思路：
WWW是Unity给我们封装的一个基于HTTP的简单类库，如果我们做很简单的下载，或者网络请求可以用这个类库，个人觉得这个封装的并不是很好，所以一般商业项目开发都不会使用这个，宁可自己去封装一个HTTP请求和下载的类库，可控性更好。仅仅是个人观点，不喜勿喷。
代码:
using UnityEngine;
using System.Collections;
using System;
using System.IO;
public class WWWLoad
{
private WWW www = null;
static System.Diagnostics.Stopwatch stopWatch = new System.Diagnostics.Stopwatch();
/// <summary>
/// 下载文件
/// </summary>
public IEnumerator DownFile(string url, string savePath, Action<WWW> process)
{
FileInfo file = new FileInfo(savePath);
stopWatch.Start();
UnityEngine.Debug.Log("Start:" + Time.realtimeSinceStartup);
www = new WWW(url);
while (!www.isDone)
{
yield return 0;
if (process != null)
process(www);
}
yield return www;
if (www.isDone)
{
byte[] bytes = www.bytes;
CreatFile(savePath, bytes);
}
}
/// <summary>
/// 创建文件
/// </summary>
/// <param name="bytes"></param>
public void CreatFile(string savePath, byte[] bytes)
{
FileStream fs = new FileStream(savePath, FileMode.Append);
BinaryWriter bw = new BinaryWriter(fs);
fs.Write(bytes, 0, bytes.Length);
fs.Flush(); //流会缓冲，此行代码指示流不要缓冲数据，立即写入到文件。
fs.Close(); //关闭流并释放所有资源，同时将缓冲区的没有写入的数据，写入然后再关闭。
fs.Dispose(); //释放流
www.Dispose();
stopWatch.Stop();
Debug.Log("下载完成,耗时:" + stopWatch.ElapsedMilliseconds);
UnityEngine.Debug.Log("End:" + Time.realtimeSinceStartup);
}
}
HTTP下载并加载AB资源
思路：
主要用的核心类是HttpWebRequest，用这个类创建的对象可以申请下载的文件的大小以及下载的进度。移动上可读写的目录是PersidentDataPath，并且各个移动设备的路径不同，这点要注意，所以我们下载的AB资源就会下载到这个目录。
效果图：
核心代码：
using UnityEngine;
using System.Collections;
using System.Threading;
using System.IO;
using System.Net;
using System;
/// <summary>
/// 通过http下载资源
/// </summary>
public class HttpDownLoad {
//下载进度
public float progress{get; private set;}
//涉及子线程要注意,Unity关闭的时候子线程不会关闭，所以要有一个标识
private bool isStop;
//子线程负责下载，否则会阻塞主线程，Unity界面会卡主
private Thread thread;
//表示下载是否完成
public bool isDone{get; private set;}
const int ReadWriteTimeOut = 2 * 1000;//超时等待时间
const int TimeOutWait = 5 * 1000;//超时等待时间
/// <summary>
/// 下载方法(断点续传)
/// </summary>
/// <param name="url">URL下载地址</param>
/// <param name="savePath">Save path保存路径</param>
/// <param name="callBack">Call back回调函数</param>
public void DownLoad(string url, string savePath,string fileName, Action callBack, System.Threading.ThreadPriority threadPriority = System.Threading.ThreadPriority.Normal)
{
isStop = false;
System.Diagnostics.Stopwatch stopWatch = new System.Diagnostics.Stopwatch();
//开启子线程下载,使用匿名方法
thread = new Thread(delegate() {
stopWatch.Start();
//判断保存路径是否存在
if (!Directory.Exists(savePath))
{
Directory.CreateDirectory(savePath);
}
//这是要下载的文件名，比如从服务器下载a.zip到D盘，保存的文件名是test
string filePath = savePath + "/"+ fileName;
//使用流操作文件
FileStream fs = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.Write);
//获取文件现在的长度
long fileLength = fs.Length;
//获取下载文件的总长度
UnityEngine.Debug.Log(url+" "+fileName);
long totalLength = GetLength(url);
Debug.LogFormat("<color=red>文件:{0} 已下载{1}M，剩余{2}M</color>",fileName,fileLength/1024/1024,(totalLength- fileLength)/ 1024/1024);
//如果没下载完
if(fileLength < totalLength)
{
//断点续传核心，设置本地文件流的起始位置
fs.Seek(fileLength, SeekOrigin.Begin);
HttpWebRequest request = HttpWebRequest.Create(url) as HttpWebRequest;
request.ReadWriteTimeout = ReadWriteTimeOut;
request.Timeout = TimeOutWait;
//断点续传核心，设置远程访问文件流的起始位置
request.AddRange((int)fileLength);
Stream stream = request.GetResponse().GetResponseStream();
byte[] buffer = new byte[1024];
//使用流读取内容到buffer中
//注意方法返回值代表读取的实际长度,并不是buffer有多大，stream就会读进去多少
int length = stream.Read(buffer, 0, buffer.Length);
//Debug.LogFormat("<color=red>length:{0}</color>" + length);
while (length > 0)
{
//如果Unity客户端关闭，停止下载
if(isStop) break;
//将内容再写入本地文件中
fs.Write(buffer, 0, length);
//计算进度
fileLength += length;
progress = (float)fileLength / (float)totalLength;
//UnityEngine.Debug.Log(progress);
//类似尾递归
length = stream.Read(buffer, 0, buffer.Length);
}
stream.Close();
stream.Dispose();
}
else
{
progress = 1;
}
stopWatch.Stop();
Debug.Log("耗时: " + stopWatch.ElapsedMilliseconds);
fs.Close();
fs.Dispose();
//如果下载完毕，执行回调
if(progress == 1)
{
isDone = true;
if (callBack != null) callBack();
thread.Abort();
}
UnityEngine.Debug.Log ("download finished");
});
//开启子线程
thread.IsBackground = true;
thread.Priority = threadPriority;
thread.Start();
}
/// <summary>
/// 获取下载文件的大小
/// </summary>
/// <returns>The length.</returns>
/// <param name="url">URL.</param>
long GetLength(string url)
{
UnityEngine.Debug.Log(url);
HttpWebRequest requet = HttpWebRequest.Create(url) as HttpWebRequest;
requet.Method = "HEAD";
HttpWebResponse response = requet.GetResponse() as HttpWebResponse;
return response.ContentLength;
}
public void Close()
{
isStop = true;
}
}
多线程下载文件
思路：
多线程下载思路是计算一个文件包大小，然后创建几个线程，计算每一个线程下载的始末下载的位置，最后是合并成一个整体的文件包写入到本地。
效果图：
核心代码：
using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Net;
using UnityEngine;
using System.Threading;
public class MultiHttpDownLoad : MonoBehaviour
{
string savePath = string.Empty;
string FileName = "ClickEffect.apk";
//string resourceURL = @"http://www.aladdingame.online/wuzhang/Resources/ClickEffect.apk";// @"http://www.dingxiaowei.cn/birdlogo.png";
string resourceURL = @"http://www.dingxiaowei.cn/ClickEffect.apk";
string saveFile = string.Empty;
public int ThreadNum { get; set; }
public bool[] ThreadStatus { get; set; }
public string[] FileNames { get; set; }
public int[] StartPos { get; set; }
public int[] FileSize { get; set; }
public string Url { get; set; }
public bool IsMerge { get; set; }
private int buffSize = 1024;
DateTime beginTime;
void Start()
{
#if UNITY_EDITOR || UNITY_STANDALONE_WIN
savePath = Application.streamingAssetsPath;
#elif UNITY_ANDROID
savePath = Application.persistentDataPath;;
#endif
saveFile = Path.Combine(savePath, FileName);
DownDoad();
}
void Init(long fileSize)
{
if (ThreadNum == 0)
ThreadNum = 5;
ThreadStatus = new bool[ThreadNum];
FileNames = new string[ThreadNum];
StartPos = new int[ThreadNum];//下载字节起始点
FileSize = new int[ThreadNum];//该进程文件大小
int fileThread = (int)fileSize / ThreadNum;//单进程文件大小
int fileThreade = fileThread + (int)fileSize % ThreadNum;//最后一个进程的资源大小
for (int i = 0; i < ThreadNum; i++)
{
ThreadStatus[i] = false;
FileNames[i] = i.ToString() + ".dat";
if (i < ThreadNum - 1)
{
StartPos[i] = fileThread * i;
FileSize[i] = fileThread;
}
else
{
StartPos[i] = fileThread * i;
FileSize[i] = fileThreade;
}
}
}
void DownDoad()
{
UnityEngine.Debug.Log("开始下载 时间:" + System.DateTime.Now.ToString());
beginTime = System.DateTime.Now;
Url = resourceURL;
long fileSizeAll = 0;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
fileSizeAll = request.GetResponse().ContentLength;
Init(fileSizeAll);
System.Threading.Thread[] threads = new System.Threading.Thread[ThreadNum];
HttpMultiThreadDownload[] httpDownloads = new HttpMultiThreadDownload[ThreadNum];
for (int i = 0; i < ThreadNum; i++)
{
httpDownloads[i] = new HttpMultiThreadDownload(request, this, i);
threads[i] = new System.Threading.Thread(new System.Threading.ThreadStart(httpDownloads[i].Receive));
threads[i].Name = string.Format("线程{0}:", i);
threads[i].Start();
}
StartCoroutine(MergeFile());
}
IEnumerator MergeFile()
{
while (true)
{
IsMerge = true;
for (int i = 0; i < ThreadNum; i++)
{
if (ThreadStatus[i] == false)
{
IsMerge = false;
yield return 0;
System.Threading.Thread.Sleep(100);
break;
}
}
if (IsMerge)
break;
}
int bufferSize = 512;
string downFileNamePath = saveFile;
byte[] bytes = new byte[bufferSize];
FileStream fs = new FileStream(downFileNamePath, FileMode.Create);
FileStream fsTemp = null;
for (int i = 0; i < ThreadNum; i++)
{
fsTemp = new FileStream(FileNames[i], FileMode.Open);
while (true)
{
yield return 0;
buffSize = fsTemp.Read(bytes, 0, bufferSize);
if (buffSize > 0)
fs.Write(bytes, 0, buffSize);
else
break;
}
fsTemp.Close();
}
fs.Close();
Debug.Log("接受完毕!!!结束时间:" + System.DateTime.Now.ToString());
Debug.LogError("下载耗时:" + (System.DateTime.Now - beginTime).TotalSeconds.ToString());
yield return null;
DeleteCacheFiles();
}
private void DeleteCacheFiles()
{
for (int i = 0; i < ThreadNum; i++)
{
FileInfo info = new FileInfo(FileNames[i]);
Debug.LogFormat("Delete File {0} OK!", FileNames[i]);
info.Delete();
}
}
}
public class HttpMultiThreadDownload
{
private int threadId;
private string url;
MultiHttpDownLoad downLoadObj;
private const int buffSize = 1024;
HttpWebRequest request;
public HttpMultiThreadDownload(HttpWebRequest request, MultiHttpDownLoad downLoadObj, int threadId)
{
this.request = request;
this.threadId = threadId;
this.url = downLoadObj.Url;
this.downLoadObj = downLoadObj;
}
public void Receive()
{
string fileName = downLoadObj.FileNames[threadId];
var buffer = new byte[buffSize];
int readSize = 0;
FileStream fs = new FileStream(fileName, System.IO.FileMode.Create);
Stream ns = null;
try
{
request.AddRange(downLoadObj.StartPos[threadId], downLoadObj.StartPos[threadId] + downLoadObj.FileSize[threadId]);
ns = request.GetResponse().GetResponseStream();
readSize = ns.Read(buffer, 0, buffSize);
showLog("线程[" + threadId.ToString() + "] 正在接收 " + readSize);
while (readSize > 0)
{
fs.Write(buffer, 0, readSize);
readSize = ns.Read(buffer, 0, buffSize);
showLog("线程[" + threadId.ToString() + "] 正在接收 " + readSize);
}
fs.Close();
ns.Close();
}
catch (Exception er)
{
Debug.LogError(er.Message);
fs.Close();
}
showLog("线程[" + threadId.ToString() + "] 结束!");
downLoadObj.ThreadStatus[threadId] = true;
}
private void showLog(string processing)
{
Debug.Log(processing);
}
}
线程下载速度跟线程的关系呈钟罩式关系，也就是说适量的线程数量会提高下载速度，但并不是说线程数越多就越好，因为线程的切换和资源的整合也是需要时间的。下面就列举下载单个文件，创建的线程数和对应的下载时间：
- 单线程
- 5个线程
- 15个线程
这里我是1M的带宽，下载的是一个300KB左右的资源，一般不会做多线程下载单一资源，多线程下载一般用于下载多个资源，除非单一资源真的很大才有多线程下载，然后做合包操作。
Demo下载
http://git.oschina.net/dingxiaowei/UnityResourceDownload
关注后续更新请点start或者fork，感谢！
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