null http response in flutter

Question

i am developing a mobile application with flutter and laravel at the back end, i made an api to add new record, and when i test the api with Thunder client, it worked perfectly, but when i call it from flutter i got null response.

this is how the error looks lik

final _messengerState = scaffoldKey.currentState; // this variable is for the snackbar
scanParticipant() async {
    Map data = {
      'event': 1,
      'participant': 11,
      'recorder': 6,
    };
    print(data);

    Response response = await _crud.postRequest(addParticipantRoute, data);
    ...
  }

postRequest(String url, Map data) async {
    try {
      var response = await http.post(Uri.parse(url),
          headers: {"Accept": "application/json"}, body: data);
      return response;
    } catch (e) {
      print('Error catch $e');
    }
  }

and the backend

public function addRecord(Request $request)
    {

        $fields = $request->validate([
            'event' => 'required|integer',
            'participant' => 'required|integer',
            'recorder' => 'required|integer'
        ]);

        $user = Record::where('event',$fields['event'])->where('participant',$fields['participant'])->first();
        
        if($user == null) 
        {
            Record::create([
                'event' => $fields['event'],
                'participant' => $fields['participant'],
                'recorder' => $fields['recorder'],
                'moment' => Carbon::now()->addHour(),
            ]);

            return response([
                'message' => 'success',
            ],201);
        }else {
            return response([
                'message' => 'already scanned'
            ],422);
        }
        
    }

note : i login before trying this function

Answer 1

I fixed the problem later. The problem was in the data variable, I should turn all the fields into string then send it.

Map data = {
  'event': '1',
  'participant': '11',
  'recorder': '6',
};