Persisting Data with SQLite Using sqflite

dependencies:
  flutter:
    sdk: flutter
  sqflite: ^2.0.0+4
  path

import 'package:sqflite/sqflite.dart';
import 'package:path/path.dart';

class DBHelper {
  static final DBHelper _instance = DBHelper._internal();
  factory DBHelper() => _instance;
  DBHelper._internal();

  static Database? _db;

  Future<Database> get database async {
    if (_db != null) return _db!;
    final dbPath = await getDatabasesPath();
    final path = join(dbPath, 'notes.db');
    _db = await openDatabase(
      path,
      version: 1,
      onCreate: (db, version) => db.execute(
        'CREATE TABLE notes(id INTEGER PRIMARY KEY AUTOINCREMENT, title TEXT, content TEXT)',
      ),
    );
    return _db!;
  }
}

class Note {
  final int? id;
  final String title;
  final String content;

  Note({this.id, required this.title, required this.content});

  Map<String, dynamic> toMap() {
    return {'id': id, 'title': title, 'content': content};
  }

  factory Note.fromMap(Map<String, dynamic> map) {
    return Note(
      id: map['id'],
      title: map['title'],
      content: map['content'],
    );
  }
}

// Inside DBHelper class
Future<int> insertNote(Note note) async {
  final db = await database;
  return await db.insert('notes', note.toMap());
}

Future<List<Note>> fetchNotes() async {
  final db = await database;
  final maps = await db.query('notes', orderBy: 'id DESC');
  return List.generate(maps.length, (i) => Note.fromMap(maps[i]));
}

Future<int> updateNote(Note note) async {
  final db = await database;
  return db.update('notes', note.toMap(),
      where: 'id = ?', whereArgs: [note.id]);
}

Future<int> deleteNote(int id) async {
  final db = await database;
  return db.delete('notes', where: 'id = ?', whereArgs: [id]);
}

import 'package:flutter/material.dart';
import 'db_helper.dart';
import 'note.dart';

void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(home: NoteList());
  }
}

class NoteList extends StatefulWidget {
  @override
  _NoteListState createState() => _NoteListState();
}

class _NoteListState extends State<NoteList> {
  late Future<List<Note>> _noteList;

  @override
  void initState() {
    super.initState();
    _refreshNotes();
  }

  void _refreshNotes() {
    _noteList = DBHelper().fetchNotes();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Flutter SQLite Demo')),
      body: FutureBuilder<List<Note>>(
        future: _noteList,
        builder: (ctx, snap) {
          if (!snap.hasData) return Center(child: CircularProgressIndicator());
          final notes = snap.data!;
          return ListView.builder(
            itemCount: notes.length,
            itemBuilder: (_, i) => ListTile(
              title: Text(notes[i].title),
              subtitle: Text(notes[i].content),
            ),
          );
        },
      ),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.add),
        onPressed: () async {
          await DBHelper().insertNote(
            Note(title: 'New Note', content: 'Details here'),
          );
          setState(_refreshNotes);
        },
      ),
    );
  }
}