unity WWW加载进度条

using UnityEngine;
using System.Collections;

public class testProgress : MonoBehaviour {

　　 void Start () {
        StartCoroutine (getWWW());
    }

    IEnumerator getWWW(){
        WWW www = new WWW ("http://192.168.1.106/app/s01.mp3");
        string progress;
        while(!www.isDone){
            progress=(((int)(www.progress * )) % ) + "%";
            Debug.Log (progress);
            yield return ;
        }
        if(www.error!=null){
            Debug.Log ("loading error:"+www.url);
        }else{
            progress="100%";
            Debug.Log (progress);
            //enter complete code
        }
    }

}