Unity网络正常状态下优先加载网络图片，否则加载本地缓存图片

程序运行后，将获取网络上下载的照片，缓存更新至本地，再次开启无网状态下或网络图片传输异常情况下，程序将读取本地缓存图片。

using UnityEngine;
using System.Collections;
using System.IO;
using System;
using UnityEngine.Events;

/// <summary>
/// 图片缓存
/// </summary>
//namespace Tools.Cache
//{
    public class CacheImage
    {
        private static CacheImage instences = null;
        private string path = //Application.persistentDataPath;
#if UNITY_EDITOR || UNITY_STANDALONE_WIN
        Application.dataPath + "/StreamingAssets/Cache";
#elif UNITY_IPHONE || UNITY_ANDROID
        Application.persistentDataPath;
#else
        string.Empty;
#endif
        private string name = "{0}.png";

        private static UnityAction<Texture2D> cacheEvent;
        private static MonoBehaviour mono;

        public static CacheImage Cache(MonoBehaviour mb, UnityAction<Texture2D> callback)
        {
            cacheEvent = callback;
            mono = mb;
            if (instences == null)
            {
                instences = new CacheImage();
            }
            return instences;
        }
        public void DownLoad(string url, string identifyId)
        {
            if (mono != null)
            {   
            //if (!string.IsNullOrEmpty(url))
            //{
            // //判断是否有缓存，无缓存则网络加载
            //mono.StartCoroutine(LoadTexture(url, identifyId));
            //}
            //else
            //{
            //    mono.StartCoroutine(LoadLocalTexture(url, identifyId));
            //} 


            mono.StartCoroutine(SlectLoadTexture(url, identifyId));
            }
        }

        private IEnumerator SlectLoadTexture(string url, string identifyId)
        {
            if (!string.IsNullOrEmpty(url))
            {
                yield return LoadNetWorkTexture(url, identifyId);
            }
        else
        {
            yield return LoadLocalTexture(url, identifyId);
        }
    }






        /// <summary>
        /// 判断是否本地有缓存,如果有则读取本地的资源，否则读取网络资源
        /// </summary>
        /// <param name="url"></param>
        /// <returns></returns>
        private IEnumerator LoadTexture(string url, string identifyId)
        {
            if (!string.IsNullOrEmpty(url))
            {
                if (!File.Exists(Path.Combine(path, string.Format(name, identifyId))))
                {
                    yield return LoadNetWorkTexture(url, identifyId);
                }
                else
                {
                    yield return LoadLocalTexture(url, identifyId);
                }
            }
        }
        /// <summary>
        /// 本地已缓存
        /// </summary>
        /// <param name="url"></param>
        /// <returns></returns>
        private IEnumerator LoadLocalTexture(string url, string identifyId)
        {
            //已在本地缓存  
            string filePath = "file:///" + Path.Combine(path, string.Format(name, identifyId));
            WWW www = new WWW(filePath);
            yield return www;
        //Debug.Log(www.texture);
        //if (true)
        //{
        cacheEvent.Invoke(www.texture);
        //}


    }
        /// <summary>
        /// 本地未缓存
        /// </summary>
        /// <param name="url"></param>
        /// <returns></returns>
        private IEnumerator LoadNetWorkTexture(string url, string identifyId)
        {
            WWW www = new WWW((new Uri(url)).AbsoluteUri);
            yield return www;

            if (!string.IsNullOrEmpty(www.error)&& File.Exists(Path.Combine(path, string.Format(name, identifyId))))
            {
                Debug.Log(string.Format("Failed to load image: {0}, {1}", url, www.error));
            yield return LoadLocalTexture(url, identifyId);
            //yield break;
             }

        else
        {
#if UNITY_EDITOR || UNITY_STANDALONE_WIN
            if (!Directory.Exists(path))
            {
                Directory.CreateDirectory(path);//创建新路径
            }
#endif

            try
            {
                //判断网络状态
                if ( Application.internetReachability != NetworkReachability.NotReachable)
                {
                    Debug.Log(Application.internetReachability);
                    Texture2D image = www.texture;
                    //将图片保存至缓存路径  
                    byte[] pngData = image.EncodeToPNG();
                    File.WriteAllBytes(Path.Combine(path, string.Format(name, identifyId)), pngData);
                    cacheEvent.Invoke(www.texture);
                }
            }
            catch 
            {

                Debug.Log(1111);
            }
             
            //else
            //{
            //    File.WriteAllBytes(Path.Combine(path, string.Format(name, identifyId)),null);
            //}
  

        }


    }
    }
//}