#if  UNITY_ANDROID

        string  s = Application.streamingAssetsPath + "/s/ss.txt";

         string filePath = Application.persistentDataPath + "/s";

        if (!File.Exists(filePath+ "/ss.txt"))

        {

            using (WWW www = new WWW(s))

            {

                yield return www;

                if (!string.IsNullOrEmpty(www.error))

                {

                    Debug.Log(www.error);

                }

                else

                {

                    if (!Directory.Exists(filePath))

                    {

                        //创建文件夹

                        Directory.CreateDirectory(filePath);

                    }

                    File.WriteAllBytes(filePath+ "/ss.txt", www.bytes);

                }

            }

        }

#endif