Unity3d C# HttpWebRequest 异步下载文件

最近一直在把公司游戏迁移到支持ARM64，中间出现了很多BUG或者Unity目前不支持操作的问题，这两天遇到异步HttpWebRequest不支持的问题，因为之前一直没有接触，所以也趁机学习了下相关使用。

下面通过一个例子，来使用HttpWebRequest异步下载一个ZIP文件。

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

public class RequestState
{
const int m_buffetSize = 1024;
public StringBuilder m_requestData;
public byte[] m_bufferRead;
public HttpWebRequest m_request;
public HttpWebResponse m_response;
public Stream m_streamResponse;

public RequestState()
{
m_bufferRead = new byte[m_buffetSize];
m_requestData = new StringBuilder("");
m_request = null;
m_streamResponse = null;
}
}

public class NewBehaviourScript : MonoBehaviour {

FileStream fileStream=null;

// Use this for initialization
void Start ()
{
fileStream = new FileStream("disunity_v0.3.4.zip", FileMode.Create);

DownloadMusicAsyn();
}

void DownloadMusicAsyn()
{
Debug.Log("DownloadMusicAsyn Thread Start");

try
{

HttpWebRequest myHttpWebRequest = (HttpWebRequest)WebRequest.Create("http://dev.thisisgame.com.cn/disunity_v0.3.4.zip");

RequestState myRequestState = new RequestState();
myRequestState.m_request = myHttpWebRequest;

Debug.Log("BeginGetResponse Start");
//异步获取;
IAsyncResult result = (IAsyncResult)myHttpWebRequest.BeginGetResponse(new AsyncCallback(RespCallback), myRequestState);

Debug.Log("BeginGetResponse End");
}
catch (System.Exception ex)
{
Debug.LogError(ex.ToString());
}

}

void RespCallback(IAsyncResult result)
{
Debug.Log("RespCallback 0");

try
{
RequestState myRequestState = (RequestState)result.AsyncState;
HttpWebRequest myHttpWebRequest = myRequestState.m_request;

Debug.Log("RespCallback EndGetResponse");
myRequestState.m_response = (HttpWebResponse)myHttpWebRequest.EndGetResponse(result);

Stream responseStream = myRequestState.m_response.GetResponseStream();
myRequestState.m_streamResponse = responseStream;

//开始读取数据;
IAsyncResult asyncreadresult = responseStream.BeginRead(myRequestState.m_bufferRead, 0, 1024, new AsyncCallback(ReadCallBack), myRequestState);

return;
}
catch (System.Exception ex)
{
Debug.LogError(ex.ToString());
}
}

void ReadCallBack(IAsyncResult result)
{
Debug.Log("ReadCallBack");
try
{
RequestState myRequestState = (RequestState)result.AsyncState;
Stream responseStream = myRequestState.m_streamResponse;
int read = responseStream.EndRead(result);

Debug.Log("read size =" + read);

if (read > 0)
{
//将接收的数据写入;
fileStream.Write(myRequestState.m_bufferRead, 0, 1024);
fileStream.Flush();
//fileStream.Close();

//继续读取数据;
myRequestState.m_bufferRead = new byte[1024];
IAsyncResult asyncreadresult = responseStream.BeginRead(myRequestState.m_bufferRead, 0, 1024, new AsyncCallback(ReadCallBack), myRequestState);
}
}
catch (System.Exception ex)
{
Debug.LogError(ex.ToString());
}
}

void TimeoutCallback(object state, bool timeout)
{
if (timeout)
{
HttpWebRequest request = state as HttpWebRequest;
if (request!=null)
{
request.Abort();
}

}
}

// Update is called once per frame
void Update () {

}
}