Jisho-Study-Tool/lib/view/components/search/language_selector.dart

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

class LanguageSelector extends StatefulWidget {
  const LanguageSelector();

  @override
  _LanguageSelectorState createState() => new _LanguageSelectorState();
}

class _LanguageSelectorState extends State<LanguageSelector> {
  late final SharedPreferences prefs;
  late List<bool> isSelected;

  @override
  void initState() {
    super.initState();
    isSelected = [false, false, false];

    SharedPreferences.getInstance()
      .then((prefs) {
        this.prefs = prefs;
        setState(() {
          isSelected = _getSelectedStatus() ?? isSelected;
        });
      });
  }

  void _updateSelectedStatus() async {
    await prefs.setStringList('languageSelectorStatus',
      isSelected
        .map((b) => b ? '1' : '0')
        .toList());
  }

  List<bool>? _getSelectedStatus() {
    return prefs
      .getStringList('languageSelectorStatus')
      ?.map((s) => s == '1')
      .toList();
  }

  @override
  Widget build(BuildContext context) {
    return ToggleButtons(
      isSelected: isSelected,
      children: <Widget> [
        _LanguageOption("Auto"),
        _LanguageOption("日本語"),
        _LanguageOption("English")
      ],
      selectedColor: Colors.blue,
      onPressed: (int buttonIndex) {
        setState(() {
          for (var i in Iterable.generate(isSelected.length)) {
            isSelected[i] = i == buttonIndex;
          }
          _updateSelectedStatus();
        });
      },
    );
  }

}

class _LanguageOption extends StatelessWidget {
  final String language;

  const _LanguageOption(this.language);

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: EdgeInsets.symmetric(vertical: 10.0, horizontal: 20.0),
      child: Center(child: Text(language)),
    );
  }
}