使用 $http 访问原始 XHR 对象

我需要访问原始数据XMLHttpRequest对象在支持它的浏览器上添加文件上传进度回调。这是可能的，还是我必须自己构建原始请求？如果是这样，我该如何包装生的XMLHttpRequest在承诺对象中？

我模拟了$http调用构建自定义XMLHttpRequest像这样：

uploadFile(file, progressHandler) {
  var xhr = new XMLHttpRequest(),
      deferred = $q.defer();

  xhr.open("POST", "your/path", true); // method, url, async
  xhr.setRequestHeader("Content-Type", file.type || "application/octet-stream");
  xhr.onreadystatechange = function (e) {
    if (xhr.readyState == 4) {
      $rootScope.$apply(function () {
        // Construct a response object similar to a regular $http call
        //
        // data – {string|Object} – The response body transformed with the transform functions.
        // status – {number} – HTTP status code of the response.
        // headers – {function([headerName])} – Header getter function.
        // config – {Object} – The configuration object that was used to generate the request.
        var r = {
          data: xhr.response,
          status: xhr.status,
          headers: xhr.getResponseHeader,
          config: {}
        };
        if (r.status == 200) {
          deferred.resolve(r);
        } else {
          deferred.reject(r);
        }
      });
    }
  };
  if (progressHandler && xhr.upload) {
    xhr.upload.addEventListener('progress', function(e) {
      progressHandler((e.loaded / e.total), e);
    }, false);
  }
  // This is only available in XHR2, provide multipart fallback
  // if necessary
  xhr.send(file);

  return deferred.promise;
}