hive_store.dart

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

/// Stores tokens using a Hive store.
/// Depends on the Hive plugin: https://pub.dev/packages/hive
class HiveStore extends TokenStore {
  static const keyToken = "auth_token";

  static Future<HiveStore> create() async {
    // Make sure you call both:
    // Hive.init(storePath);
    // Hive.registerAdapter(TokenAdapter(), adapterId);

    var box = await Hive.openBox("auth_store",
        compactionStrategy: (entries, deletedEntries) => deletedEntries > 50);
    return HiveStore._internal(box);
  }

  final Box _box;

  HiveStore._internal(this._box);

  @override
  Token read() => _box.get(keyToken);

  @override
  void write(Token token) => _box.put(keyToken, token);

  @override
  void delete() => _box.delete(keyToken);
}

class TokenAdapter extends TypeAdapter<Token> {
  @override
  final typeId = 42;

  @override
  void write(BinaryWriter writer, Token token) =>
    writer.writeMap(token.toMap());

  @override
  Token read(BinaryReader reader) =>
      Token.fromMap(reader.readMap().map<String, dynamic>(
          (key, value) => MapEntry<String, dynamic>(key, value)));
}

With

environment:
  sdk: '>=2.12.0 <3.0.0'

This code will not work as it does not support the null safe (and it extends TokenStore).
You will get some errors.

In order to fix this you need to add ? to both @override Token read() and @override void write(Token token) override methods like this:

  @override
  Token? read() => _box.get(keyToken);

  @override
  void write(Token? token) => _box.put(keyToken, token);