unity3d从streamingassets拷贝到persistentassets

using UnityEngine;
using UnityEngine.UI;
using System.Collections;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;

public class main : MonoBehaviour
{
    public string fileName = "img.png";

    public Image img_persistent;
    public Image img_streaming;

    public Button btn_copy;
    public Button btn_clear;

    public Button btn_close;

    //public Text txt_info;

    // Use this for initialization
    void Start()
    {
        img_persistent.sprite = null;
        img_streaming.sprite = null;
        LoadImage_from_Streaming(fileName, img_streaming);

        btn_copy.onClick.AddListener(() =>
        {
            Debug.Log("click btn copy!");
            if (img_persistent.sprite == null)
            {
                StartCoroutine(copy(fileName));
            }
        });

        btn_clear.onClick.AddListener(() =>
        {
            clear();
        });

        btn_close.onClick.AddListener(() =>
        {
            Application.Quit();
        });
    }

    /// <summary>
    /// 将streaming path 下的文件copy到对应用
    /// 为什么不直接用io函数拷贝，原因在于streaming目录不支持，
    /// 不管理是用getStreamingPath_for_www，还是Application.streamingAssetsPath，
    /// io方法都会说文件不存在
    /// </summary>
    /// <param name="fileName"></param>
    IEnumerator copy(string fileName)
    {
        string src = getStreamingPath_for_www() + fileName;
        string des = Application.persistentDataPath + "/" + fileName;
        Debug.Log("des:" + des);
        Debug.Log("src:" + src);
        WWW www = new WWW(src);
        yield return www;
        if (!string.IsNullOrEmpty(www.error))
        {
            Debug.Log("www.error:" + www.error);
        }
        else
        {
            //des = Application.persistentDataPath + "/" + fileName;
            if (File.Exists(des))
            {
                File.Delete(des);
            }
            FileStream fsDes = File.Create(des);
            fsDes.Write(www.bytes, 0, www.bytes.Length);
            fsDes.Flush();
            fsDes.Close();

            LoadImage_from_Persistent(fileName, img_persistent);
        }
        www.Dispose();
    }

    void clear()
    {
        img_persistent.sprite = null;
        string des = Application.persistentDataPath + "/" + fileName;
        if (File.Exists(des))
        {
            File.Delete(des);
        }
    }

    /// <summary>
    /// Load Image from Persistent folder
    /// </summary>
    /// <param name="path"></param>
    /// <param name="uiImg"></param>
    void LoadImage_from_Persistent(string path, UnityEngine.UI.Image uiImg)
    {
        path = getPersistentPath_for_www() + path;
        Debug.Log("persistent path:" + path);
        StartCoroutine(wwwLoadImage(path, uiImg));
    }

    /// <summary>
    /// Load Image from Streaming folder
    /// </summary>
    /// <param name="path"></param>
    /// <param name="uiImg"></param>
    void LoadImage_from_Streaming(string path, UnityEngine.UI.Image uiImg)
    {
        path = getStreamingPath_for_www() + path;
        Debug.Log("streaming path:" + path);
        StartCoroutine(wwwLoadImage(path, uiImg));
    }

    IEnumerator wwwLoadImage(string path, UnityEngine.UI.Image uiImg)
    {
        WWW www = new WWW(path);
        yield return www;
        if (!string.IsNullOrEmpty(www.error))
        {
            Debug.Log("www.error:" + www.error);
        }
        uiImg.sprite = Sprite.Create(www.texture, new Rect(new Vector2(0, 0), new Vector2(www.texture.width, www.texture.height)), Vector2.zero);
        www.Dispose();
    }

    //void LogToText(string log)
    //{
    //    Debug.Log(log);
    //    txt_info.text += "\n" + log;
    //}

    string getStreamingPath_for_www()
    {
        string pre = "file://";
#if UNITY_EDITOR
        pre = "file://";
#elif UNITY_ANDROID
        pre = "";
#elif UNITY_IPHONE
	    pre = "file://";
#endif
        string path = pre + Application.streamingAssetsPath + "/";
        return path;
    }

    string getPersistentPath_for_www()
    {
        string pre = "file://";
#if UNITY_EDITOR || UNITY_STANDALONE_WIN
        pre = "file:///";
#elif UNITY_ANDROID
        pre = "file://";
#elif UNITY_IPHONE
        pre = "file://";
#endif
        string path = pre + Application.persistentDataPath + "/";
        return path;
    }
}