HarmonyOS Native怎么更新UI?

class MainViewStatus{  
  @Track  backgroundColor: number;  
  constructor() {  
    this.backgroundColor = 0x55ff0000  
  }  
  setBackgroundColor(value: number){  
    this.backgroundColor = value;  
  }  
}  
@Entry  
@Component  
struct Index {  
  @State message: string = 'Hello World'  
  @State @Watch('onBackgroundColorChange') mainViewStatus:MainViewStatus = new MainViewStatus()  
  onBackgroundColorChange(){  
    this.message = '111'  
  }  
  build() {  
    Row() {  
      Column() {  
        Text(this.message)  
          .fontSize(50)  
          .fontWeight(FontWeight.Bold) t  
          .onClick(() => {  
              engine.createMainView(this.mainViewStatus)  
            })  
      }  
      .width('100%')  
    }  
    .height('100%')  
    .backgroundColor(this.mainViewStatus.backgroundColor)  
  }  
}

void ArkCore::createMainView(const CallbackInfo &info) {  
    NValue obj = info[0];  
    std::vector<NValue> args;  
    args.push_back(Number::New(info.Env(), 0xff00ff00));  
    obj.ToObject().Get("setBackgroundColor").As<Function>().Call(obj, args);  
}