Unity 下载服务器文件资源

    /// <summary>
    /// Untiy下载服务器的某个文件资源
    /// </summary>
    /// <param name="url">文件的服务器地址</param>
    /// <param name="localPath">文件需要保存的本地地址</param>
    /// <returns></returns>
    public static IEnumerator DownLoadFileFormURL(string url, string localPath)
    {
        Debug.Log("下载地址:" + url + ",保存路径：" + localPath);
        UnityWebRequest headRequest = UnityWebRequest.Head(url);
        yield return headRequest.SendWebRequest();
        if (!string.IsNullOrEmpty(headRequest.error))
        {
            Debug.LogError("获取下载的文件大小失败:" + headRequest.error);
            yield break;
        }
        ulong totalLength = ulong.Parse(headRequest.GetResponseHeader("Content-Length"));//获取文件总大小
        Debug.Log("获取大小" + totalLength);
        headRequest.Dispose();

        // 以下是获取文件名的代码逻辑
        string fileName = Path.GetFileName(url);
        Debug.Log("文件名: " + fileName);


        UnityWebRequest Request = UnityWebRequest.Get(url);
        //localPath += totalFileName;
        localPath = Path.Combine(localPath, fileName);
        Request.downloadHandler = new DownloadHandlerFile(Path.Combine(localPath));//append设置为true文件写入方式为接续写入，不覆盖原文件。
        FileInfo file = new FileInfo(localPath);
        ulong fileLength = (ulong)file.Length;
        Debug.Log("文件总共大小:" + fileLength + ",totalLength=" + totalLength);
        //设置文件从什么位置开始下载和写入
        Request.SetRequestHeader("Range", "bytes=" + fileLength + "-");
        if (fileLength < totalLength)
        {
            Request.SendWebRequest();
            while (!Request.isDone)
            {
                double p = (Request.downloadedBytes + fileLength) / (double)totalLength;
                //进度条.value = (float)progress;
                Debug.Log("下载进度:" + (p * 100).ToString("F2") + "%");
                yield return null;
            }
        }
        if (string.IsNullOrEmpty(Request.error))
        {
            Debug.Log("下载成功:" + localPath);
        }
        else
        {
            Debug.LogError("下载失败:" + Request.error);
        }
        Request.Dispose();
    }