hive_in_flutter.md

Hive in Flutter

Hive supports all platforms supported by Flutter.

Initialize Flutter Apps

Before you can open a box, Hive needs to know where it can store its data. Android and iOS have very strict rules for allowed directories. You can use the path_provider package to get a valid directory.

The hive_flutter package provides the Hive.initFlutter() extension method which handles everything for you.

ValueListenable

If you want your widgets to refresh based on the data stored in Hive, you can use the ValueListenableBuilder. The box.listenable() method provides a ValueListenable which can also be used with the provider package.

import 'package:flutter/material.dart';

import 'package:hive/hive.dart';
import 'package:hive_flutter/hive_flutter.dart';

void main() async {
  await Hive.initFlutter();
  await Hive.openBox('settings');
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Demo Settings',
      home: Scaffold(
        body: ValueListenableBuilder<Box>(
          valueListenable: Hive.box('settings').listenable(),
          builder: (context, box, widget) {
            return Center(
              child: Switch(
                value: box.get('darkMode', defaultValue: false),
                onChanged: (val) {
                  box.put('darkMode', val);
                },
              ),
            );
          },
        ),
      ),
    );
  }
}

Each time the value associated with darkMode changes, the builder is called, and the Switch widget refreshed.

Listening for specific keys

It is good practice to refresh widgets only if necessary. If a widget only depends on specific keys in your box, you can provide the keys parameter:

ValueListenableBuilder<Box>(
  valueListenable: Hive.box('settings').listenable(keys: ['firstKey', 'secondKey']),
  builder: (context, box, widget) {
    // build widget
  },
)

Async calls

Many of the Hive methods like put() or delete() are asynchronous. Handling async calls in Flutter is not fun because you have to use FutureBuilder or StreamBuilder and handle exceptions.

The good news is that you don't have to await all the Futures returned by Hive. Changes are applied instantly, even if the Future has not finished yet. If you want to make sure that a write operation is successful, just await its Future.