通过使用下载文件UnityEngine.WWW
,我得到了错误
OverflowException:数字溢出。
我发现错误是由结构本身引起的,因为字节数组的字节数超过了int.MaxValue可以分配的字节数(〜2GB)。
通过使用返回数组会引发该错误www.bytes
,这意味着框架可能以其他方式存储数组。
如何以其他方式访问下载的数据,或者有更大文件的替代方法?
public IEnumerator downloadFile()
{
WWW www = new WWW(filesource);
while(!www.isDone)
{
progress = www.progress;
yield return null;
}
if(string.IsNullOrEmpty(www.error))
{
data = www.bytes; // <- Errormessage fired here
}
}
新答案(Unity 2017.2及更高版本)
UnityWebRequest
与一起使用DownloadHandlerFile
。该DownloadHandlerFile
班是新的,直接,同时防止高内存使用情况来下载和保存文件。
IEnumerator Start()
{
string url = "http://dl3.webmfiles.org/big-buck-bunny_trailer.webm";
string vidSavePath = Path.Combine(Application.persistentDataPath, "Videos");
vidSavePath = Path.Combine(vidSavePath, "MyVideo.webm");
//Create Directory if it does not exist
if (!Directory.Exists(Path.GetDirectoryName(vidSavePath)))
{
Directory.CreateDirectory(Path.GetDirectoryName(vidSavePath));
}
var uwr = new UnityWebRequest(url);
uwr.method = UnityWebRequest.kHttpVerbGET;
var dh = new DownloadHandlerFile(vidSavePath);
dh.removeFileOnAbort = true;
uwr.downloadHandler = dh;
yield return uwr.SendWebRequest();
if (uwr.isNetworkError || uwr.isHttpError)
Debug.Log(uwr.error);
else
Debug.Log("Download saved to: " + vidSavePath.Replace("/", "\\") + "\r\n" + uwr.error);
}
老答案(Unity 2017.1及更低版本)如果要在下载文件时访问每个字节,请使用
这样的问题是为什么制作Unity的UnityWebRequest
原因,但是它不能直接工作,因为WWW
API现在在UnityWebRequest
Unity的最新版本中在API之上实现,这意味着如果您在WWW
API出错的情况下也可能会得到相同的结果错误UnityWebRequest
。即使它能正常工作,您在带有Android等小型RAM的移动设备上也可能会遇到问题。
要做的是使用UnityWebRequest的DownloadHandlerScript
功能,该功能允许您分块下载数据。通过分块下载数据,可以防止导致溢出错误。该WWW
API没有实现这个功能,因此UnityWebRequest
并DownloadHandlerScript
必须用于下载数据块中的数据。您可以在这里阅读其工作原理。
虽然这可以解决您当前的问题,但是在尝试使用保存大数据时,您可能会遇到另一个内存问题File.WriteAllBytes
。用于FileStream
保存并仅在下载完成后关闭。
创建一个自定义UnityWebRequest
文件,以如下方式大块下载数据:
using System;
using System.IO;
using UnityEngine;
using UnityEngine.Networking;
public class CustomWebRequest : DownloadHandlerScript
{
// Standard scripted download handler - will allocate memory on each ReceiveData callback
public CustomWebRequest()
: base()
{
}
// Pre-allocated scripted download handler
// Will reuse the supplied byte array to deliver data.
// Eliminates memory allocation.
public CustomWebRequest(byte[] buffer)
: base(buffer)
{
Init();
}
// Required by DownloadHandler base class. Called when you address the 'bytes' property.
protected override byte[] GetData() { return null; }
// Called once per frame when data has been received from the network.
protected override bool ReceiveData(byte[] byteFromServer, int dataLength)
{
if (byteFromServer == null || byteFromServer.Length < 1)
{
Debug.Log("CustomWebRequest :: ReceiveData - received a null/empty buffer");
return false;
}
//Write the current data chunk to file
AppendFile(byteFromServer, dataLength);
return true;
}
//Where to save the video file
string vidSavePath;
//The FileStream to save the file
FileStream fileStream = null;
//Used to determine if there was an error while opening or saving the file
bool success;
void Init()
{
vidSavePath = Path.Combine(Application.persistentDataPath, "Videos");
vidSavePath = Path.Combine(vidSavePath, "MyVideo.webm");
//Create Directory if it does not exist
if (!Directory.Exists(Path.GetDirectoryName(vidSavePath)))
{
Directory.CreateDirectory(Path.GetDirectoryName(vidSavePath));
}
try
{
//Open the current file to write to
fileStream = new FileStream(vidSavePath, FileMode.OpenOrCreate, FileAccess.ReadWrite);
Debug.Log("File Successfully opened at" + vidSavePath.Replace("/", "\\"));
success = true;
}
catch (Exception e)
{
success = false;
Debug.LogError("Failed to Open File at Dir: " + vidSavePath.Replace("/", "\\") + "\r\n" + e.Message);
}
}
void AppendFile(byte[] buffer, int length)
{
if (success)
{
try
{
//Write the current data to the file
fileStream.Write(buffer, 0, length);
Debug.Log("Written data chunk to: " + vidSavePath.Replace("/", "\\"));
}
catch (Exception e)
{
success = false;
}
}
}
// Called when all data has been received from the server and delivered via ReceiveData
protected override void CompleteContent()
{
if (success)
Debug.Log("Done! Saved File to: " + vidSavePath.Replace("/", "\\"));
else
Debug.LogError("Failed to Save File to: " + vidSavePath.Replace("/", "\\"));
//Close filestream
fileStream.Close();
}
// Called when a Content-Length header is received from the server.
protected override void ReceiveContentLength(int contentLength)
{
//Debug.Log(string.Format("CustomWebRequest :: ReceiveContentLength - length {0}", contentLength));
}
}
如何使用:
UnityWebRequest webRequest;
//Pre-allocate memory so that this is not done each time data is received
byte[] bytes = new byte[2000];
IEnumerator Start()
{
string url = "http://dl3.webmfiles.org/big-buck-bunny_trailer.webm";
webRequest = new UnityWebRequest(url);
webRequest.downloadHandler = new CustomWebRequest(bytes);
webRequest.SendWebRequest();
yield return webRequest;
}
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