HarmonyOS WebView如何监听this.webViewController.backward()方法执行完成？

build() { 
  Column() { 
    Button('backward') 
      .onClick(() => { 
        try { 
          this.controller.backward(); 
        } catch (error) { 
          let e: business_error.BusinessError = error as business_error.BusinessError; 
          console.error(`ErrorCode: ${e.code},  Message: ${e.message}`); 
        } 
      }) 
    Web({ src: $rawfile('index.html'), controller: this.controller }) 
  } 
}