相关疑难解决方法(0)

我想上传一张图片,我正在使用http.Client()来发送请求,

static uploadImage(String id, File file) {
  var httpClient = createHttpClient();

  Map<String, String> headers = new Map<String, String>();
  headers.putIfAbsent("Authorization", () => "---");
  headers.putIfAbsent("Content-Type", () => "application/json");

  var body=new List();
  body.add(id.)
  httpClient.post(URL_UPLOADIMAGE,headers: headers,body: ,encoding: )
}

请求的正文和编码部分应该是什么？