filling in upload function

upload.dart

  final String endPoint = 'http://10.0.2.2:8000/analyze';
  void _upload(File file) async {
    String fileName = file.path.split('/').last;
    print(fileName);

    FormData data = FormData.fromMap({
      "file": await MultipartFile.fromFile(
        file.path,
        filename: fileName,
      ),
    });

    Dio dio = new Dio();

    dio.post(endPoint, data: data).then((response) {
      var jsonResponse = jsonDecode(response.toString());
      var testData = jsonResponse['histogram_counts'].cast<double>();
      var averageGrindSize = jsonResponse['average_particle_size'];
    }).catchError((error) => print(error));
  }