HarmonyOS 如何不通过Web组件获取UserAgent

import web_webview from '@ohos.web.webview'; 
 
@Entry 
@Component 
struct WebComponent { 
  controller: web_webview.WebviewController = new web_webview.WebviewController(); 
  @State userAgent: string = '' 
 
  build() { 
    Column() { 
      Web({ src: '', controller: this.controller }) 
        .width(0).height(0) 
        .onControllerAttached(() => { 
          this.userAgent = this.controller.getUserAgent(); 
          console.log("userAgent: " + this.userAgent); 
        }) 
      Column(){ 
        Text('11111111111') 
      }.width('100%').height('100%') 
    } 
  } 
}