HttpAsyn**重點內容**
下載採用協同，固定更新 每次從下載佇列中取一個下載包
下載完成 通過下載包回撥通知資料關心者

HttpPackage**重點內容**
下載包 包含 回撥 方法，http請求url

對下載的資料 用jeson 解析，通過定義對應的資料物件，用JsonMapper 取轉換，注意定義的資料物件一定要和jeson內容對應

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using LitJson;
using System;
/// <summary>
 

/// 載入資料包
/// </summary>
public class HttpPackage
{
    /// <summary>
    /// 下載地址
    /// </summary>
    public string url;
    /// <summary>
    /// 下載完成
    /// </summary>
    public Action<string> Downloaded;

    public HttpPackage( string url, Action< string> callBack)
    {  
        this
 
.url = url;
        Downloaded = callBack;
    }

}

public class HttpAsyn : MonoBehaviour {
    public static HttpAsyn Instance;

    private int coroutineCount;
    private int limitCoroutineCount=5;
    private Queue<HttpPackage> listPackage = new Queue<HttpPackage>();
    private void
 
 Awake()
    {
        Instance = this;
    }

    /// <summary>
    /// 進入下載佇列
    /// </summary>
    /// <param name="package"></param>
    public void EnterLoadingQueue(HttpPackage package)
    {
        if (!listPackage.Contains(package))
        {
            listPackage.Enqueue(package);
        } 
    }
    /// <summary>
    ///  進入下載佇列
    /// </summary>
    /// <param name="package">陣列</param>
    public void EnterLoadingQueue(HttpPackage[] package)
    {
        for (int i = 0; i < package.Length; i++)
        {
            if (listPackage.Contains(package[i]))
            {
                continue;
            }
            listPackage.Enqueue(package[i]);
        }
    }

    /// <summary>
    /// 下載資料
    /// </summary>
    public void OnUpdate()
    {
        if (listPackage.Count>0&&coroutineCount<limitCoroutineCount)
        {
            HttpPackage package = listPackage.Dequeue();
            try
            {
                StartCoroutine(AsynLoadingData(package));
            }
            catch (System.Exception ex)
            {

            }
        }
    }
    /// <summary>
    /// 非同步下載資料
    /// </summary>
    /// <param name="package"></param>
    /// <returns></returns>
    public IEnumerator AsynLoadingData(HttpPackage package)
    {
        coroutineCount += 1;
        using (WWW www=new WWW(package.url))
        {
            yield return www;
            if (www.error!=null)
            {
                Debug.LogError(this.name + ".AsynLoadingData（）下載失敗" + "url:" + package.url);
                EnterLoadingQueue(package);

            }
            else
            {
               if (package.Downloaded!=null)
               {
                    if (string.IsNullOrEmpty(www.text) )
                    {
                        Debug.LogError(this.name + ".AsynLoadingData() 獲取的 www.text 為空 ");
                    }
                    else
                    {
                        package.Downloaded(www.text);
                    }              
               }
            }
            coroutineCount -= 1;
        }            
    }

    public void OnRemovePackage()
    {
        if(HttpAsyn.Instance!=null)
        {
            StopAllCoroutines();
            listPackage.Clear();
            coroutineCount = 0;

        }

    }

    private void Update()
    {
        OnUpdate();
    }
}


public class AnalysisJson
{
    public static T  Analy<T>(string text) where T:class
    {
        T o = JsonMapper.ToObject<T>(text);

        if (o!=null)
        {
            return o ;
        }
        return default(T);
    }

    public static T GetData<T>(string text) where T : class
    {
        JsonData table = AnalysisJson.Analy<JsonData>(text);
        T t = JsonMapper.ToObject<T>(table["retBody"].ToJson());
        return t;
    }
}