Dart:http post上传到谷歌硬盘

在使用命令行curl命令成功上载文件后，我尝试将文件上载到Dart中的google Drive：

curl -X POST -L \
    -H "Authorization: Bearer $access_token" \
    -F "metadata={name : 'test_send_file.zip'};type=application/json;charset=UTF-8" \
    -F "file=@test_send_file.zip;type=application/zip" \
    "https://www.googleapis.com/upload/drive/v3/files?uploadType=multipart"

---

dart版本：

import 'package:http/http.dart' as http;
import 'package:http_parser/http_parser.dart';

final access_token = "....";

main() async {
  File first = File('test_send_file.zip');
  Uri uri = Uri.parse(
      'https://www.googleapis.com/upload/drive/v3/files?uploadType=multipart');

  http.MultipartRequest request = new http.MultipartRequest('POST', uri);

  request.headers["Authorization"] = "Bearer $access_token";
  request.fields['metadata'] =
      "{name : test_send_file.zip};type=application/json;charset=UTF-8";
  request.files.add(await http.MultipartFile.fromPath('test_send_file.zip', first.path,
      contentType: new MediaType('application', 'zip')));
  print("request.toString: " + request.toString());
  http.StreamedResponse response = await request.send();
  print(response.statusCode);
}

---

我收到一个状态代码错误请求：

400

---

有人能帮我向google drive in Dart发送一个文件http请求吗？

当你想向

多部分请求添加一个更复杂的表单项时，你可以将其作为文件添加。（是的，有点奇怪……）

替换
请求.字段。将…
添加为

  request.files.add(http.MultipartFile.fromString(
    'metadata',
    json.encode({'name': 'test_send_file.zip'}),
    contentType: MediaType('application', 'json'),
  ));

谢谢你，这很有效！我已将
request.fields['metadata']..
和
request.files.add…
替换为
request.files.add.
已被此问题困扰。这是行不通的。这个名字总是没有名字。似乎元数据需要作为多部分/相关内容类型传递，但我得到了400