/// <summary>
    /// 网络地址加载图片
    /// </summary>
    /// <param name="url">地址</param>
    /// <param name="raw">图片显示位置</param>
    public void loadImage(string url,RawImage raw)
    {
        string imageName = GetImageName(url);
        string myUrl = FilePath + imageName + ".png";
        isImgExist = File.Exists(url);
        if (isImgExist)
        {
            StartCoroutine(startLoad(myUrl, imageName, raw));
        }
        else
        {
            if (IsValidUrl(url))
            {
                StartCoroutine(startLoad(url, imageName, raw));
            }
            else
            {
                Debug.Log("网址不对!");
                raw.texture = sprite.texture;
            }
        }

    }

    /// <summary>
    /// 加载图片
    /// </summary>
    /// <param name="url">图片地址</param>
    /// <param name="name">唯一不重复变量</param>
    /// <param name="raw">图片显示位置</param>
    /// <returns></returns>
    IEnumerator startLoad(string url, string name, RawImage raw)
    {
        //加载图片
        using (UnityWebRequest www = UnityWebRequestTexture.GetTexture(url))
        {
            yield return www.SendWebRequest();
            if (www.result == UnityWebRequest.Result.ConnectionError)
            {
                //Debug.Log(www.error);
                raw.texture = sprite.texture;
            }
            else
            {
                /*这里把贴图转换的过程放到了后台线程来完成，
                并且相比于直接脚本加载图片做了优化，减少了内存分配*/
                Debug.Log(www);
                Texture2D tx = DownloadHandlerTexture.GetContent(www);
                raw.texture = tx;
                //raw.GetComponent<RectTransform>().sizeDelta = new Vector2(imageWidth, (tx.height * 1.0f / tx.width) * imageWidth);
                //图片保存到本地
                if (!isImgExist)
                {
                    Byte[] bytes = tx.EncodeToPNG();
                    File.WriteAllBytes(FilePath + "\\" + name + ".png", bytes);
                }
            }

        }
    }

    /// <summary>
    /// 判断网址对不对
    /// </summary>
    /// <param name="url"></param>
    /// <returns></returns>
    private bool IsValidUrl(string url)
    {
        string pattern = @"^(http|https):\/\/([a-zA-Z0-9]+[-\.]?)+(:[0-9]{1,5})?(\/.*)?$";
        return System.Text.RegularExpressions.Regex.Match(url, pattern).Success;
    }

    /// <summary>
    /// 从网址中获取名图片名字
    /// </summary>
    /// <param name="url"></param>
    /// <returns></returns>
    private string GetImageName(string url)
    {
        if (!IsValidUrl(url)) return "";
        string str;
        int lastSlashIndex = url.LastIndexOf('/');
        if (lastSlashIndex != -1)
        {
            str = url.Substring(lastSlashIndex + 1); // 通过Substring()函数删除最后一个'/'之前的部分
        }
        else
        {
            Debug.Log("地址有问题！");
            str = "";
        }
        int lastSuffixIndex = str.LastIndexOf('.');//删除后缀
        str = str.Remove(lastSuffixIndex, str.Length - lastSuffixIndex);
        return str;
    }