carrot/assets/Script/MainScene.ts

import { _decorator, Component, director, instantiate, Node, Prefab,  resources,  Sprite,  SpriteFrame,  UITransform, Vec3 } from 'cc';
const { ccclass, property } = _decorator;

@ccclass('MainScene')
export class MainScene extends Component {
    @property(Prefab)
    countDown:Prefab;

    countDownTS:any = null;

    bg: Node = null;

    protected onLoad(){
    }

    start() {
        let countDown = instantiate(this.countDown);
        this.node.addChild(countDown);
        //获取倒计时预制体脚本
        this.countDownTS = countDown.getComponent("CountDown");

        this.bg = this.node.getChildByPath("GameRoot/Bg");
        const path: string = "Res/Theme/Theme1/BG0/BG1-hd.pvr.ccz"
        resources.load(path, SpriteFrame, (error: Error, frame: SpriteFrame)=>{
            if(error){
                console.error("No found!")
                //console.log(frame)
            } else{
                this.bg.getComponent(Sprite).spriteFrame = frame;
            }
        })
    }

    update(deltaTime: number) {
        //倒计时结束，游戏开始
        if(this.countDownTS.isOver){
            
        }
    }
}