HarmonyOS Web组件实现异步的请求拦截

异步返回的代码示例如下：

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:xxx.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
    }
  })