如何显示场景的加载进度，cc.loader.onProgress新版本已经没了

Creator 2.x
#1

搜索了下了论坛，大多说的都是用cc.loader.onProgress
但是现在1.9新版本已经都干掉cc.loader.onProgress
还有什么办法获取场景加载进度么？

#2 
const { ccclass, property } = cc._decorator

@ccclass
export default class SceneMgr extends cc.Component {
    static loadScene(sceneName: string, onLoaded?) {
        cc.loader.loadRes('LoadingScene', cc.Prefab, (err, res) => {
            if (err) {
                return
            }

            let node: cc.Node = cc.instantiate(res)
            cc.director.getScene().addChild(node)

            let comp = node.getComponent(SceneMgr)
            comp.preloadScene(sceneName, onLoaded)
        })
    }

    @property(cc.ProgressBar) progressBar: cc.ProgressBar = null
    @property(cc.Node) progressEffect: cc.Node = null

    private preloadScene(sceneName, onLoaded?) {
        let info = cc.director._getSceneUuid(sceneName)
        if (info) {
            cc.director.emit(cc.Director.EVENT_BEFORE_SCENE_LOADING, sceneName)
            cc.loader.load(
                { uuid: info.uuid, type: 'uuid' },
                (completedCount: number, totalCount: number, item: any) => {
                    let step = completedCount / totalCount
                    this.updateProgress(step)
                },
                (error, asset) => {
                    if (error) {
                        cc.error(1210, sceneName, error.message)
                    } else {
                        cc.director.loadScene(sceneName)
                    }
                    if (onLoaded) {
                        onLoaded(error, asset)
                    }
                }
            )
        } else {
            cc.error('Error PreloadScene: ' + sceneName)
        }
    }

    private updateProgress(progress: number) {
        this.progressBar.progress = progress
        this.progressEffect.x = -643 / 2 + 643 * progress
    }
}
#3

这个方法没有

#4

_getSceneUuid 这个方法要貌似是私有的？

#5

遇到同样的问题，有解决了吗？