HarmonyOS Web组件onInterceptRequest做资源拦截时建议用同步返回还是异步返回？

async getFile(url : string) { 
  const fileName = url.split("/").pop(); 
  const filePath = this.context.cacheDir + '/'+fileName; 
  const flag=this.hasFile(filePath); 
  if(!flag){ 
    await this.downloadImage(url, filePath); 
  } 
  let file = await fs.openSync(filePath, fs.OpenMode.READ_ONLY); 
  let arrayBuffer = new ArrayBuffer(4096); 
  return file.fd; 
} 
Web({ src: $rawfile('iframe.html'), controller: this.webviewController }) 
  .onInterceptRequest((event) => { 
    if (event) { 
      console.log('url123456:' + event.request.getRequestUrl()) 
    } 
 
    const url = event!.request.getRequestUrl(); 
 
    console.log(url.endsWith(".jpg") + '123456') 
    if (!url.endsWith(".jpg")) return null; 
    try { 
      let url2='https://1.jpg'; 
      this.getFile(url2).then(fd => { 
        this.responseweb.setResponseData(fd); 
        this.responseweb.setResponseCode(200); 
        this.responseweb.setReasonMessage('OK'); 
        this.responseweb.setResponseIsReady(true); 
      }); 
      this.responseweb.setResponseMimeType('image/*'); 
      this.responseweb.setResponseIsReady(false); 
      console.log(this.responseweb.getResponseData().toString+"123456") 
      return this.responseweb; 
 
    } catch (error) { 
      return null 
    } 
  })