以角度 7 显示进度条以进行文件上传

Question

我正在使用以下代码：

addDataFile(data):Observable<any>{

  let currentUser = JSON.parse(localStorage.getItem("currentUser"));
  let url = `${this.baseUrl}/das/dataFile`;
    let httpHeaders = new HttpHeaders({
      Authorization: `${currentUser.idToken}`,
    });
    return this.http.post(url, data, {
      headers: httpHeaders,
      reportProgress: true,
      observe: 'events'
    });
}

但作为回应，我得到了未定义的 httpevent