HarmonyOS鸿蒙Next中@State状态声明的变量发生改变后，UI没有发生变化

HarmonyOS鸿蒙Next中@State状态声明的变量发生改变后，UI没有发生变化

import web_webview from '@ohos.web.webview'
import { TitleBar } from 'common'
@Entry
@Component
struct WebPage {
  controller: web_webview.WebviewController = new web_webview.WebviewController()
  showTitleBar: boolean = true
  isLocal: boolean = false
  [@State](/user/State) title: string = "加载中"
  URL: string = 'www.baidu.com';
  callback = {
    test: (data1, data2, data3) => {
      console.log("data1:" + data1)
      console.log("data2:" + data2)
      console.log("data3:" + data3)
      return "AceString"
    },
    toString: () => {
      console.log('toString' + "interface instead.")
    }
  }
  build() {
    Column() {
      if(this.showTitleBar){
        TitleBar({title:this.title})
      }
      Web({
        src: this.isLocal?$rawfile(this.URL):this.URL, 
        controller: this.controller 
      })
      .javaScriptAccess(true).zoomAccess(false).horizontalScrollBarAccess(false)
      .verticalScrollBarAccess(false)
      .onTitleReceive((event) => {
        this.title = event.title
      })
      .javaScriptProxy({
        object: this.callback,
        name: "ciyun",
        methodList: ["test", "toString"],
        controller: this.controller,
      })
    }
    .width('100%')
    .height('100%')
  }
}

上面代码我写了一个webview，自定义了一个titlebar，当网页加载完成后，回调onTitleReceive，给title赋值，debug发现赋值成功，但是Ui没有更新。请问是什么问题呢