callback无法成功更新UI

import { IBaseModelListener } from './IBaseModelListener'

export class TestViewModel implements IBaseModelListener {
  newsViewModel: NewsViewModel = new NewsViewModel(this)
  title: string = "aaa"

  onLoadFinish(data: string) {
    setTimeout(() => {
      this.title = "直接在TestViewModel里延时修改title可以成功更新UI，而通过另外一个类的listener的callback修改同样的title不会更新UI，请问有什么办法解决么？"
    }, 300)
  }

  refresh() {
    //通过另外一个类的listener的callback修改同样的title不会更新UI"
    this.newsViewModel.load()
/*    //"直接在TestViewModel里延时修改title可以成功更新UI"
    setTimeout(() => {
      hilog.error(0x0000, "Test", "直接在TestViewModel里延时修改title可以成功更新UI")
      this.title = "bbbb"
    }, 300)*/
  }
}

export class NewsViewModel {
  iBaseModelListener: IBaseModelListener = null;

  constructor(iBaseModelListener:IBaseModelListener) {
    this.iBaseModelListener = iBaseModelListener
  }

  load() {
    this.iBaseModelListener.onLoadFinish([])
  }
}