db_helper.dart

// class name
class SqfliteDatabaseHelper {

//instantiate an object that can be called anywhere in the app
  static final SqfliteDatabaseHelper instance = SqfliteDatabaseHelper._init();

  //table name stored in a string
  final String demandNoticeTable = 'demandNoticeTable';

 //database initialization
  SqfliteDatabaseHelper._init();

  //Database object
  static Database _db;

 //Database creation
  Future<Database> get db async {
    if (_db != null) {
      return _db;
    }
    _db = await initDb('ekirss.db');
    return _db;
  }

 //Method to create database
  Future<Database> initDb(String filePath) async {
    final dbPath = await getDatabasesPath();
    final path = join(dbPath, filePath);
    print(dbPath);
    var openDb = await openDatabase(
      path,
      version: 2,
      onCreate: _createDb,
    );
    return openDb;
  }

//method to create table
  Future _createDb(Database db, int version) async {
    final idType = 'INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL';
    final textType = 'TEXT';
    await db.execute('''
      CREATE TABLE $demandNoticeTable(
        ${DemandFields.id} $idType,
        ${DemandFields.propertyId} $textType,
      )''');
}

//Method to add data to the table 
  Future<DemandNoticeModel> addDemand(DemandNoticeModel demandNotice) async {
    final db = await instance.db;

    final id = await db.insert(demandNoticeTable, demandNotice.toJson());
    return demandNotice.copy(id: id);
  }

//Method to fetch data from the table
  Future<List<dynamic>> fetchAllDemand() async {
    final db = await instance.db;
    List<dynamic> demandList= [];
    try {
      final maps =
          await db.query(SqfliteDatabaseHelper.instance.demandNoticeTable);
      for (var item in maps) {
        contactList.add(DemandNoticeModel.fromJson(item));
      }
    } catch (e) {
      print(e.toString());
    }
    return demandList;
  }

  //Method to close database
  Future close() async {
    final dab = await instance.db;

    dab.close();
  }
}