//非同步載入
IEnumerator LoadAsyncTest()
    {
        WWW www = WWW.LoadFromCacheOrDownload("http://127.0.0.1:80/abc/obj1.ab", 8);
        yield return www;
        Debug.Log("www載入完成");
        //取得AssetBundle
        AssetBundle ab = www.assetBundle;
        //非同步載入物件
        AssetBundleRequest request = ab.LoadAssetAsync("cubeasset", typeof(GameObject)); //指定了型別為GameObject
        //等待非同步完成
        yield return request;
        Debug.Log("非同步載入完成");
        //獲得載入物件的引用,這個時候是在記憶體中
        GameObject obj = request.asset as GameObject;
        //克隆一份物件顯示在場景中
        Instantiate(obj);
        //從記憶體解除安裝AssetBundle
        ab.Unload(false);
    }