sqlite - How can I open a database already created in flutter and show its data?

Question

I am new to flutter and have come across a question in flutter.

1 . I already have a Database created in SQLITE.

2 . the database is called "nutrition_program.db". It contains 2 tables called "food" and "food group".

3 . I only need to show the data, I don't need to create, delete or update.

4. Only managed to copy the database from assets.

the examples i have seen all create the database. Is there a way to just read them and display the data?

I managed to do something but it only shows me everything in null, but it tells me the total data in the table

this is MAIN.DART

import 'package:flutter/material.dart';
import 'package:pruebabd/dbhelper.dart';

void main() => runApp(AppPrueba());

class AppPrueba extends StatefulWidget {
  @override
  _AppPruebaState createState() => _AppPruebaState();
}

class _AppPruebaState extends State<AppPrueba> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar:
        AppBar(title: Text('Prueba SQLITE'),),
        body: FutureBuilder(
          future: grupo_alimentos(),
            builder: (context, AsyncSnapshot snapshot) {
              if (!snapshot.hasData) {
                return Center(child: CircularProgressIndicator());
              } else {
                return Container(
                  child: ListView.builder(
                    itemCount: snapshot.data.length,
                    scrollDirection: Axis.vertical,
                    itemBuilder: (BuildContext context, int index){
                    return Card(
                        child: positionedBlock(context, snapshot.data[index]));
                    },
                  ),
                );
              }
            } //cierrre Snapshot
            ),
      ),
    );
  }
}


Widget positionedBlock(BuildContext context, GrupoAlimentos grupoAlimentos) {
  return Align(
    alignment: Alignment.topCenter,
                child: Padding(
                  padding: const EdgeInsets.only(right: 8.0, top: 8.0),
                  child: ListTile(
                    title:Text('${grupoAlimentos.ID}',
                      style: TextStyle(
                        fontSize: 18,
                        fontWeight: FontWeight.bold,
                      ),
                    ),
                    subtitle:  Text(
                      '${grupoAlimentos.Nombre_Grupo}',
                      style: TextStyle(
                        fontSize: 18,
                      ),
                    ),
                  ),
                ),
  );
}

and the dbhelper.dart file

import 'dart:io';
import 'package:flutter/services.dart';
import 'package:sqflite/sqflite.dart';
import 'package:path/path.dart';

class DbHelper{
  Future initDB() async{
    final dbpath=await getDatabasesPath();
    final path = join (dbpath, "programa_nutricion.db");//nombre de la base de datos a migrar
    final exist = await databaseExists(path);
    if (exist){
        print('La base de Datos existe');
    }else{
      print('Creando una copia de la base de datos desde Assets');
      try {
        await Directory(dirname(path)).create(recursive: true);
      } catch(_) {}
      ByteData data = await rootBundle.load(join("assets","programa_nutricion.db"));
      List<int> bytes = data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
      await File(path).writeAsBytes(bytes, flush: true);
      print('BASE DE DATOS COPIADA');
    }
    await openDatabase(path);
  }
}

class GrupoAlimentos{
  final int ID;
  final String Nombre_Grupo;
  GrupoAlimentos({this.ID,this.Nombre_Grupo});
}

final Future<Database> database = getDatabasesPath().then((String path) {
  return openDatabase(join(path, 'programa_nutricion.db'));
});

Future<List<GrupoAlimentos>> grupo_alimentos() async {
  // Obtiene una referencia de la base de datos
  final Database db = await database;

  // Consulta la tabla por todos los grupos.
  final List<Map<String, dynamic>> maps = await db.query('grupo_alimentos');

  // Convierte List<Map<String, dynamic> en List<GrupoAlimentos>.
  return List.generate(maps.length, (i) {
    return GrupoAlimentos(
      ID: maps[i]['id'],
      Nombre_Grupo: maps[i]['nombre'],
     );
  });
}

When executing the APP it gives me this result showing me the 24 records that I have in said database. But with NULL

I attached the image

https://i.stack.imgur.com/VKWbJ.png

Answer 1

等待大神答复