Hive Flutter Usage - flutter

Question

I am a newbee at Flutter and Hive, just learning. Here are some questions:
I am using Value Listenable Builder, when I press the "Person age Up" person1 age is not updated, but if I press the setstate then is updated.
How to auto update?
Hive is a database; if I press the "Add person", it adds, and I see when I press "Print person lenght" but when reloaded the app person length is changed to 1 again, all adds removed:
import 'package:flutter/material.dart';
import 'package:hive/hive.dart';
import 'package:hive_flutter/hive_flutter.dart';
import 'departmentClass.dart';
import 'person.dart';
void main() async {
await Hive.initFlutter('test');
Hive.registerAdapter(DepartmentAdapter());
Hive.registerAdapter(PersonAdapter());
await Hive.openBox<Department>('testBox');
runApp(MyApp());
}
class MyApp extends StatefulWidget {
#override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
final Box testBox = Hive.box<Department>('testBox');
#override
Widget build(BuildContext context) {
if (testBox.isEmpty) {
final List<Person> personsAll = [];
final person1 = new Person(23, "Maria");
personsAll.add(person1);
var mydepartment = new Department(34, "newD", personsAll);
Hive.box<Department>('testBox').put("01", mydepartment);
}
return ValueListenableBuilder(
valueListenable: testBox.listenable(),
builder: (context, box, widget) {
return MaterialApp(
home: SafeArea(
child: Scaffold(
appBar: AppBar(
title: Text("Hive Test"),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Text("Hive Sample"),
RaisedButton(
child: Text("Clear Box"),
onPressed: () {
Hive.box<Department>('testBox').clear();
},
),
Text("Person1 Age Now: " + box.get("01").persons[0].age.toString()),
RaisedButton(
child: Text("Person age UP"),
onPressed: () {
box.get("01").persons[0].age++;
print(box.get("01").persons[0].age);
},
),
RaisedButton(
child: Text("Set State"),
onPressed: () {
setState(() {});
},
),
RaisedButton(
child: Text("Add person "),
onPressed: () {
final person2 = new Person(23, "Maria");
box.get("01").persons.add(person2);
},
),
RaisedButton(
child: Text("Print person lenght "),
onPressed: () {
print("Persons: " + Hive.box<Department>('testBox').get("01").persons.length.toString());
},
)
],
)),
),
),
);
},
);
}
}

Answer 1

First of all when you open a box it is better to declare it's type in generic;
final Box<Department> testBox = Hive.box<Department>('testBox');
Secondly if you want to notify the box that you're listening via ValueListenableBuilder, you need to put the value inside the box every time you changed the value;
box.get("01").persons[0].age++;
// this will notify the valuelistenablebuilder
box.put("01", box.get("01"));
print(box.get("01").persons[0].age);

Answer 2

I have written an app where I used both Hive and cubits and it worked really well.
Below is AppDatabase class, where I have only one box ('book') and I open it up in the initialize() method, like below:
The whole application and tutorial is here.
const String _bookBox = 'book';
#Singleton()
class AppDatabase {
AppDatabase._constructor();
static final AppDatabase _instance = AppDatabase._constructor();
factory AppDatabase() => _instance;
late Box<BookDb> _booksBox;
Future<void> initialize() async {
await Hive.initFlutter();
Hive.registerAdapter<BookDb>(BookDbAdapter());
_booksBox = await Hive.openBox<BookDb>(_bookBox);
}
Future<void> saveBook(Book book) async {
await _booksBox.put(
book.id,
BookDb(
book.id,
book.title,
book.author,
book.publicationDate,
book.about,
book.readAlready,
));
}
Future<void> deleteBook(int id) async {
await _booksBox.delete(id);
}
Future<void> deleteAllBooks() async {
await _booksBox.clear();
}
}