显示UnityWebRequest的进度

我正在尝试使用下载assetbundle Unity Web Request 并显示进度,根据 the documentation 我需要捕获WebRequestAsyncOperation对象以查找进度,但找不到它

我尝试使用AsyncOperation和UnityWebRequestAsyncOperation,我的例程可以同时使用这两种操作,使用其中一种有什么区别?

这是我的代码:

IEnumerator DownloadModel3D()
    {
        using (UnityWebRequest uwr = UnityWebRequest.GetAssetBundle(bundleURL,1,0))
        {
            //UnityWebRequestAsyncOperation request = uwr.SendWebRequest();
            AsyncOperation request = uwr.SendWebRequest();

            while (!request.isDone)
            {
                Debug.Log(request.progress);
                yield return null;
            }


            if (uwr.isNetworkError || uwr.isHttpError)
            {
                Debug.Log(uwr.error);
            }
            else
            {
                // Get downloaded asset bundle
                AssetBundle bundle = DownloadHandlerAssetBundle.GetContent(uwr);

                assetBundleInstance = Instantiate(bundle.LoadAsset(assetName)) as GameObject;
                assetBundleInstance.transform.position = transform.position;
                assetBundleInstance.transform.localScale = new Vector3(.08f, .08f, .08f);
                assetBundleInstance.transform.SetParent(transform);
                contador.text = "Descargado: " + assetName + "\n" + bundleURL;
            }
        }
    }