HarmonyOS 页面不更新

通过改变对象的某个值刷新页面，参考以下代码:

 class  City{
  name:string
  constructor(name:string) {
    this.name = name
  }
}
@Entry
@Component
struct Index {
  @State isEnable: boolean = true
  url: string = ''
  controller: web_webview.WebviewController = new web_webview.WebviewController()
  @State city:City = new City('南京')
  build() {
    Stack(){
      Image($r('app.media.ic_app_background')).width('100%')
    
      Column(){
        Text(this.city.name).fontColor(Color.White).textAlign(TextAlign.Start)
          .margin({top:20})
        Rect({width:'90%',height:100})
          .radius(10)
          .fill(Color.Blue)
          .stroke(Color.Transparent)
          .margin({top:10})
          .onClick(()=>{
            this.city.name = '上海'
          })
      }
    }
  }
}