flutter send a JSON object and A MultipartFile to a server

I was able to send a file as MultiPart method by using the following code

static Future<ResponseStatusModel?> uploadAvatar(File file, String userId, List<String> activeAvatar) async {
print('uploadAvatar is called $activeAvatar');

ResponseStatusModel? responseModel;

print('avatar file path on profile API ${file.path} ');

try {
  var formData = FormData.fromMap({
    'userid': userId,
    'avatarActive': "$activeAvatar",
    'data': await MultipartFile.fromFile(file.path),
  });
  var response = await dio.post('https://gamification.ird.global/api/uploadavatar', data: formData);

  if (response.statusCode == 200) {
    // print(await response.stream.bytesToString());
    responseModel = responseStatusModelFromJson(response.toString());
    print("avatar upload response ${responseModel.status}");

    return responseModel;
  } else {
    print("else response from avatar upload $response.statusMessage");
    return null;
  }
} on Exception catch (e) {
  print('catch error from avatar upload API $e');
  return null;
}

}

FLUTTER HTTP

Flutter multipart request fields take only Map<String, String>. If you pass Map<String, dynamic> will arise error.

You need to encode your Map<String,dynamic> then covert to string.

if your server can decode this string you can apply my solution

THE SOLUTION FOR ME:

var data = {
      "State":"test",
      "City":"test",
      "Street": "test",
      "location":{
                "lat":1.2,
                "lang":2.1
      }
};

var header = {
  "Content-Type": 'multipart/form-data',
  "Accept": 'application/json'
};



Map<String, String> obj = {"barberAddress": json.encode(data).toString()};
var request = http.MultipartRequest("POST", Uri.parse("url here"))
  ..fields.addAll(obj)
  ..headers.addAll(header)
  ..files.addAll(files);

var streamResponse = await request.send();
var response = await http.Response.fromStream(streamResponse);
// Your result here

IN SEVER SIDE

LARAVEL:

$obj = json_decode($request["barberAddress"], true);
// Your code here

OR

$obj = json_decode($request->barberAddress, true);
// Your code here

IF IT IS HARD TO DECODE YOUR OBJECT ON SEVER USE

flutter dio package through this link : dio flutter package

I THINK MAY HELP SOMEONE

The solution to this problem is dealing with the json as a file instead of a field.Instead of using the "request.fields" method you should use the "request.files" method after generating a json file. As well as you do with the MultipartFile. This avoid to get a error from the API for a Content-Type: application/octet-stream So your code would look something like this:

Future syncLocalDataToMobileSig(
      {required EntrepriseAgricultureCharegement
          entrepriseAgricultureCharegement}) async {
    Uri uri = Uri.parse("$baseUrlMobile/new");

    var request = http.MultipartRequest("POST", uri);
    request.headers.addAll({"Content-Type": "multipart/form-data"});
    File file = File(
        "/data/user/0/com.example.app_amee/app_flutter/IMG_20220115_113910.jpg");
    var stream = http.ByteStream(file.openRead());
    stream.cast();
    var length = await file.length();
    var multipartFile = http.MultipartFile(
      "files",
      stream,
      length,
    );
   request.files.add(multipartFile);

   final jsonData = jsonEncode(entrepriseAgricultureCharegement.toJson());
   final jsonPart = http.MultipartFile.fromString(
    "objectField",
    jsonData,
    filename: 'data.json',
    contentType: MediaType('application', 'json'),
  );
    request.files.add(jsonPart);


    try {
    var streamedResponse = await request.send();
    final responseData = await streamedResponse.stream.toBytes();
    final responseString = String.fromCharCodes(responseData);
    print(responseString);
    } catch (e) {
      print("e => $e");
    }
  }