protected void CreateWWW()
        {
            if (_wwwLoader != null)
            {
                return;
            }
            _wwwLoader = WwwLoaderManager.CreateLoader(_packageFile, _packageVersion, _useCache);

            foreach (AssetLoader dependLoader in _dependLoaders.Values)
            {
                dependLoader.CreateWWW();
            }
        }
        protected void ReleaseWWW()
        {
            if (_wwwLoader == null)
            {
                return;
            }

            WwwLoaderManager.DestroyLoader(_wwwLoader);

            foreach (AssetLoader dependLoader in _dependLoaders.Values)
            {
                dependLoader.ReleaseWWW();
            }
        }