Flutter Hive: make multiple openBox

Question

I'm using Hive to make simple CRUD; in Hive Doc about open box we can declare like this:

var box = await Hive.openBox<E>('testBox');

My question: is it possible to make multiple openBox? I want something like this:

Future _openBox() async {
  var dir = await getApplicationDocumentsDirectory();
  Hive.init(dir.path);
  var box_session = await Hive.openBox("box_session");
  var box_comment = await Hive.openBox("box_comment");
  return await box_session,box_comment;
}

Answer 1

Yes you can return List
You can copy paste run full code below

code snippet

List<Box> boxList = [];
Future<List<Box>> _openBox() async {
  var dir = await getApplicationDocumentsDirectory();
  Hive.init(dir.path);
  var box_session = await Hive.openBox("box_session");
  var box_comment = await Hive.openBox("box_comment");
  boxList.add(box_session);
  boxList.add(box_comment);
  return boxList;
}

full code

import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:hive/hive.dart';

List<Box> boxList = [];
Future<List<Box>> _openBox() async {
  var dir = await getApplicationDocumentsDirectory();
  Hive.init(dir.path);
  var box_session = await Hive.openBox("box_session");
  var box_comment = await Hive.openBox("box_comment");
  boxList.add(box_session);
  boxList.add(box_comment);
  return boxList;
}

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await _openBox();
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() async{
    await boxList[0].put('name','hello');
    await boxList[1].put('name','world');

    var name1 = await boxList[0].get('name');
    var name2 = await boxList[1].get('name');

    print('name1 ${name1}');
    print('name1 ${name2}');
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

Output

I/flutter ( 8023): name1 hello
I/flutter ( 8023): name1 world

demo

Answer 2

In the above answer, to avoid errors I suggest adding data type instead of

var box_session = await Hive.openBox("box_session");
var box_comment = await Hive.openBox("box_comment");

mention your data type

Box <int> box_session = await Hive.openBox("box_session");
Box <String> box_comment = await Hive.openBox("box_comment");

In my case actually am using non-primitive type data and after registering both Adapters my successful code was as follows

Box<Class> tempClassBoxName = await Hive.openBox('tempClassBoxName')
Box<Member> tempMembersBoxName = await Hive.openBox('tempMembersBoxName');