so I'm using flutter 2.2 and I'm tring to get data from an sqlite database but it's always coming as null

    data_helper

class DataBaseHelper{
  static final _dataBaseName = 'test.db';
  static final _dataBaseVerison = 1;
  static final _tabel = 'person';

  DataBaseHelper._privateConstructor();
  static final DataBaseHelper instance = DataBaseHelper._privateConstructor();
  static Database? _database;


  Future<Database> get database async {
    if (_database != null) return _database!;
    _database = await initDatabase();
    return _database!;
  }

  @override
  Future<Database> initDatabase() async {
    var databasesPath = await getDatabasesPath();
    var path = join(databasesPath, _dataBaseName);
    var exists = await databaseExists(path);
    if (!exists) {
      try {
        await Directory(dirname(path)).create(recursive: true);
      } catch (_) {}
      ByteData data = await rootBundle.load(join("assets", _dataBaseName));
      List<int> bytes = data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
      await File(path).writeAsBytes(bytes, flush: true);
    }
    Database newDatabase = await openDatabase(path, version: _dataBaseVerison);
    return newDatabase;

  }

   getAllRows(String tabel) async {
    Database db = await instance.database;
    var result = await db.query(tabel) ;
    print("All Data : $result");
    return result.toList();
  }
}

person_model

class Person {
  Person({
      int? id, 
      String? firstname, 
      String? lastName,}){
    _id = id;
    _firstname = firstname;
    _lastName = lastName;
}

  Person.fromJson(dynamic json) {
    _id = json['id'];
    _firstname = json['Firstname'];
    _lastName = json['lastName'];
  }
  int? _id;
  String? _firstname;
  String? _lastName;

  int? get id => _id;
  String? get firstname => _firstname;
  String? get lastName => _lastName;

  Map<String, dynamic> toJson() {
    final map = <String, dynamic>{};
    map['id'] = _id;
    map['Firstname'] = _firstname;
    map['lastName'] = _lastName;
    return map;
  }

}

main

class _MyHomePageState extends State<MyHomePage> {
  DataBaseHelper dbHelper = DataBaseHelper.instance;
  List<Person> person= List.empty(growable: true);

  @override
  void initState() {
    super.initState();
    dbHelper.getAllRows('person').then((rows){
      setState(() {
        rows.forEach((row) {
          person.add(Person.fromJson(row));
        });
      });
    });
  }
  @override
  Widget build(BuildContext context)
  {
    return  Scaffold(
      appBar: AppBar(title: Text('SQLite Example')),
      body: Center(
        child: ListView.builder(
               itemCount:person.length,
               itemBuilder: (context,index){
                 return ListTile(
                   title:Text('${person[index].name}}.'),
               
                 );
               }),
      ),
    );
  }
}

data from database when I print it All Data : [{id:1,Firstname:test,lastName:test}]

so i know that when i send data to fromjason it goes as null not a string and I tried JSON.decode(row) didn't work as type 'QueryRow' is not a subtype of type 'String'

CodePudding user response：

Need to pass row data in fromJson and follow the below code

import 'package:flutter/material.dart';

const Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  List<Person> person = List.empty(growable: true);

  List<Map> data = [
    {"id": 1, "Firstname": "test", "lastName": "test"}
  ];

  @override
  void initState() {
    super.initState();
    data.forEach((row) {
      person.add(Person.fromJson(row));
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(
        scaffoldBackgroundColor: darkBlue,
      ),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        appBar: AppBar(title: Text('SQLite Example')),
        body: Center(
          child: ListView.builder(
              itemCount: person.length,
              itemBuilder: (context, index) {
                return ListTile(
                  title: Text('${person[index].firstname} ${person[index].lastName}'),
                );
              }),
        ),
      ),
    );
  }
}


class Person {
  Person({
    int? id,
    String? firstname,
    String? lastName,
  }) {
    _id = id;
    _firstname = firstname;
    _lastName = lastName;
  }

  Person.fromJson(dynamic json) {
    _id = json['id'];
    _firstname = json['Firstname'];
    _lastName = json['lastName'];
  }
  int? _id;
  String? _firstname;
  String? _lastName;

  int? get id => _id;
  String? get firstname => _firstname;
  String? get lastName => _lastName;

  Map<String, dynamic> toJson() {
    final map = <String, dynamic>{};
    map['id'] = _id;
    map['Firstname'] = _firstname;
    map['lastName'] = _lastName;
    return map;
  }
}