عدم ارسال درخواست post از داخل برنامه

با سلام خدمت مهندس حسینی

من یه سروری با node js و دیتابیس mongoDB نوشتم و از طریق postman درخواست post ارسال میکنم و داخل دیتابیس ذخیره میشه ولی نمی دونم چرا از طریق برنامه به آدرس ریکوئست نمی تونه دسترسی پیدا کنه. ممنون میشم راهنماییم کنید

کدهای فایل network.dart:

import 'package:connectivity_plus/connectivity_plus.dart';
import 'package:cool_alert/cool_alert.dart';
import 'package:engineering_services_tariff/models/tariff.dart';
import 'package:engineering_services_tariff/utils/constants.dart';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert' as convert;

class Network {
  static bool isConnected = false;

  static Future<bool> checkInternet(BuildContext context) async {
    Connectivity().onConnectivityChanged.listen((status) {
      if (status == ConnectivityResult.wifi ||
          status == ConnectivityResult.mobile) {
        isConnected = true;
      } else {
        showInternetError(context);
        isConnected = false;
      }
    });
    return isConnected;
  }

  static void showInternetError(BuildContext context) {
    CoolAlert.show(
        width: 100,
        title: "خطا",
        confirmBtnText: "باشه",
        text: "!شما به اینترنت متصل نیستید",
        confirmBtnColor: kBlueColor,
        confirmBtnTextStyle: const TextStyle(fontSize: 16, color: Colors.white),
        context: context,
        type: CoolAlertType.error);
  }

  static Uri urlGet = Uri.parse("http://localhost:3000/api/tariff-list");
  static Uri urlPost = Uri.parse("http://127.0.0.1:8000/api/supervision/add/");

  static Uri urlWithId(String id) {
    Uri url = Uri.parse("http://localhost:3000/api/tariff-list/$id/");
    return url;
  }

  static List<Tariff> tariffs = [];

  static getData() async {
    tariffs.clear();
    await http.get(Network.urlGet).then((response) {
      if (response.statusCode == 200) {
        List jsonDecode = convert.jsonDecode(response.body);
        for (var json in jsonDecode) {
          tariffs.add(Tariff.fromJson(json));
        }
      }
    });
  }

  static postData({
    required String year,
    required String field,
    required String group,
    required String price,
  }) async {
    Tariff tariff =
        Tariff(year: year, field: field, group: group, price: price);
    await http.post(Network.urlPost, body: tariff.toJson()).then((response) {});
  }
}

کدهای مربوط به add_screen.dart:

import 'package:cool_alert/cool_alert.dart';
import 'package:engineering_services_tariff/screens/calculate_screen.dart';
import 'package:engineering_services_tariff/utils/network.dart';
import 'package:engineering_services_tariff/widgets/my_button_widget.dart';
import 'package:engineering_services_tariff/widgets/my_text_field_widget.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

import '../utils/constants.dart';

class AddScreen extends StatefulWidget {
  const AddScreen({Key? key}) : super(key: key);

  static TextEditingController priceController = TextEditingController();

  @override
  State<AddScreen> createState() => _AddScreenState();
}

class _AddScreenState extends State<AddScreen> {
  // Initial Selected Value
  String fieldsDropdownValue = 'هماهنگ کننده';

  // List of items in our dropdown menu
  var fieldItems = [
    'هماهنگ کننده',
    'عمران',
    'معماری',
    'تأسیسات مکانیکی',
    'تأسیسات برقی',
  ];

  String yearDropdownValue = '1401';

  // List of items in our dropdown menu
  var yearItems = [
    '1401',
    '1400',
    '1399',
    '1398',
    '1397',
    '1396',
    '1395',
  ];

  String groupDropdownValue = 'ب';

  // List of items in our dropdown menu
  var groupItems = [
    'الف',
    'ب',
    'ج',
    'د',
  ];

  String cDropdownValue = '6 و 7 طبقه';

  // List of items in our dropdown menu
  var cItems = [
    '6 و 7 طبقه',
    '8 تا 10 طبقه',
  ];

  String dDropdownValue = '11 و 12 طبقه';

  // List of items in our dropdown menu
  var dItems = [
    '11 و 12 طبقه',
    '13 تا 15 طبقه',
    '16 طبقه و بالاتر',
  ];

  @override
  Widget build(BuildContext context) {
    String group = "";
    return Directionality(
      textDirection: TextDirection.rtl,
      child: Scaffold(
        body: SafeArea(
          child: Padding(
            padding: const EdgeInsets.all(22.0),
            child: SingleChildScrollView(
              child: Column(
                children: [
                  Row(
                    mainAxisAlignment: MainAxisAlignment.spaceAround,
                    children: [
                      DropdownButton(
                        borderRadius: BorderRadius.circular(15.0),

                        // Initial Value
                        value: fieldsDropdownValue,

                        // Down Arrow Icon
                        icon: const Icon(Icons.keyboard_arrow_down),

                        // Array list of items
                        items: fieldItems.map((String items) {
                          return DropdownMenuItem(
                            value: items,
                            child: Text(items),
                          );
                        }).toList(),
                        // After selecting the desired option,it will
                        // change button value to selected value
                        onChanged: (String? newValue) {
                          setState(() {
                            fieldsDropdownValue = newValue!;
                          });
                        },
                      ),
                      DropdownButton(
                        borderRadius: BorderRadius.circular(15.0),
                        // Initial Value
                        value: yearDropdownValue,

                        // Down Arrow Icon
                        icon: const Icon(Icons.keyboard_arrow_down),

                        // Array list of items
                        items: yearItems.map((String items) {
                          return DropdownMenuItem(
                            value: items,
                            child: Text(items),
                          );
                        }).toList(),
                        // After selecting the desired option,it will
                        // change button value to selected value
                        onChanged: (String? newValue) {
                          setState(() {
                            yearDropdownValue = newValue!;
                          });
                        },
                      ),
                    ],
                  ),
                  const SizedBox(height: 22),
                  Row(
                    mainAxisAlignment: MainAxisAlignment.spaceAround,
                    children: [
                      DropdownButton(
                        borderRadius: BorderRadius.circular(15.0),

                        // Initial Value
                        value: groupDropdownValue,

                        // Down Arrow Icon
                        icon: const Icon(Icons.keyboard_arrow_down),

                        // Array list of items
                        items: groupItems.map((String items) {
                          return DropdownMenuItem(
                            value: items,
                            child: Text(items),
                          );
                        }).toList(),
                        // After selecting the desired option,it will
                        // change button value to selected value
                        onChanged: (String? newValue) {
                          setState(() {
                            groupDropdownValue = newValue!;
                          });
                        },
                      ),
                      DropdownButton(
                        borderRadius: BorderRadius.circular(15.0),
                        // Initial Value
                        value: cDropdownValue,

                        // Down Arrow Icon
                        icon: const Icon(Icons.keyboard_arrow_down),

                        // Array list of items
                        items: cItems.map((String items) {
                          return DropdownMenuItem(
                            value: items,
                            child: Text(items),
                          );
                        }).toList(),
                        // After selecting the desired option,it will
                        // change button value to selected value
                        onChanged: (String? newValue) {
                          setState(() {
                            cDropdownValue = newValue!;
                          });
                        },
                      ),
                      DropdownButton(
                        borderRadius: BorderRadius.circular(15.0),
                        // Initial Value
                        value: dDropdownValue,

                        // Down Arrow Icon
                        icon: const Icon(Icons.keyboard_arrow_down),

                        // Array list of items
                        items: dItems.map((String items) {
                          return DropdownMenuItem(
                            value: items,
                            child: Text(items),
                          );
                        }).toList(),
                        // After selecting the desired option,it will
                        // change button value to selected value
                        onChanged: (String? newValue) {
                          setState(() {
                            dDropdownValue = newValue!;
                          });
                        },
                      )
                    ],
                  ),
                  const SizedBox(height: 22),
                  MyTextField(
                    controller: AddScreen.priceController,
                    errorText: "لطفا مبلغ تعرفه را وارد کنید",
                    hintText: "مبلغ تعرفه خدمات مهندسی (ریال)",
                    inputType: TextInputType.number,
                  ),
                  const SizedBox(height: 22),
                  MyButton(
                      child: const Text("اضافه کردن"),
                      width: double.infinity,
                      onPressed: () {
                        Network.checkInternet(context);
                        Future.delayed(const Duration(seconds: 3)).then(
                          (value) {
                            if (Network.isConnected) {
                              if (groupDropdownValue == "الف") {
                                group = "a";
                              } else if (groupDropdownValue == "ب") {
                                group = "b";
                              } else if (groupDropdownValue == "ج") {
                                if (cDropdownValue == "6 و 7 طبقه") {
                                  group = "c1";
                                } else {
                                  group = "c2";
                                }
                              } else if (groupDropdownValue == "د") {
                                if (dDropdownValue == "11 و 12 طبقه") {
                                  group = "d1";
                                } else if (dDropdownValue == "13 تا 15 طبقه") {
                                  group = "d2";
                                } else {
                                  group = "d3";
                                }
                              }
                              Network.postData(
                                  year: yearDropdownValue,
                                  field: fieldsDropdownValue,
                                  group: group,
                                  price: AddScreen.priceController.text);
                              CoolAlert.show(
                                  width: 100,
                                  title: "موفق",
                                  confirmBtnText: "باشه",
                                  text: group + " " + AddScreen.priceController.text,
                                  confirmBtnColor: kBlueColor,
                                  confirmBtnTextStyle: const TextStyle(
                                      fontSize: 16, color: Colors.white),
                                  context: context,
                                  type: CoolAlertType.success);
                              // Navigator.pop(context);
                            } else {
                              Network.showInternetError(context);
                            }
                          },
                        );
                      })
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }
}

و البته اینم از درخواست post ارسالی از طریق postman که به درستی کار میکنه: