unity文件下载（缓存+进度+不重复）/上传

使用UnityWebRequest 。

记录url，下载前比较是否已存在相同下载，存在则直接将回调添加在对应url下，统一分发下载进度、下载结果回调。下载完毕将文件缓存在app根目录下。

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Security.Cryptography;
using System.Text;
using UnityEngine;
using UnityEngine.Networking;
using UnityEngine.Rendering;

/*create by keefor on 2021/3/19*/

/// <summary>
/// 大文件资源上传下载，避免重复操作
/// </summary>
public class HttpFileHelper: ISingleton<HttpFileHelper>
{
    private class CallbackCol
    {
        public Action<DownloadHandler> end;
        public Action<float> progress;
        public Action<float> upprogress;
    }

    private  class RequestCol
    {
        public string url;
        public UnityWebRequest request;
        public List<CallbackCol> list;
    }

    private List<RequestCol> requestlist = new List<RequestCol>();

    private RequestCol FindRequest(string url,Type type)
    {
        for (int i = 0; i < requestlist.Count; i++)
        {
            if (url == requestlist[i].url&&requestlist[i].request.downloadHandler.GetType() == type) return requestlist[i];
        }

        return null;
    }
    

    private List<RequestCol> removelist = new List<RequestCol>();
    // private  Texture2D def;

    public static string rootpath {
        get { return Application.persistentDataPath + "/_cache/";}
    }
    public string requsetID; 
    public string requestHeadersKey;
    private void Awake()
    {
        // def = Resources.Load<Texture2D>("noimg"); 
        Directory.CreateDirectory(rootpath);
        requsetID = HttpManager.requsetID;
        requestHeadersKey = HttpManager.requestHeadersKey;
        
    }

    void LateUpdate()
    {
        if (requestlist.Count < 0) return;
        removelist.Clear();
        for (int i = 0; i < requestlist.Count; i++)
        {
            var req = requestlist[i];
            if (req.request == null)
            {
                removelist.Add(req);
                continue;
            }
            if (req.request.isDone)
            {
                DownloadHandler down = null;
                if (req.request.isNetworkError || req.request.isHttpError)
                {
                    // if(!req.url.StartsWith("file://"))
                    //     MsgCenter.Instance.SendMsg(new Msg_ShowRequestTip{ txt="请求失败