Settings storage example with shared_preferences

home.dart

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

class Home extends StatefulWidget {
  const Home({super.key});

  @override
  State<Home> createState() => _HomeState();
}

class _HomeState extends State<Home> {
  bool boldText = false;
  double fontSize = 16;

  @override
  void initState() {
    _initializeVariables();
    super.initState();
  }

  _initializeVariables() async {
    final SharedPreferences prefs = await SharedPreferences.getInstance();

    double? fontSizeTemp = prefs.getDouble('fontSize');
    if (fontSizeTemp != null) {
      fontSize = fontSizeTemp;
    }

    bool? boldTextTemp = prefs.getBool('boldText');
    if (boldTextTemp != null) {
      boldText = boldTextTemp;
    }

    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Ejemplo de Key/Value'),
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
      ),
      body: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        mainAxisAlignment: MainAxisAlignment.start,
        mainAxisSize: MainAxisSize.min,
        children: [
          SwitchListTile(
            value: boldText,
            title: const Text('Bold Text'),
            onChanged: (value) async {
              boldText = value;
              setState(() {});

              final SharedPreferences prefs =
                  await SharedPreferences.getInstance();
              prefs.setBool('boldText', boldText);
            },
          ),
          Row(
            children: [
              Container(
                padding: const EdgeInsets.only(left: 20),
                child: Text(fontSize.toStringAsFixed(0)),
              ),
              Expanded(
                child: Slider(
                  value: fontSize,
                  min: 10,
                  max: 30,
                  onChanged: (value) {
                    fontSize = value;
                    setState(() {});
                  },
                  onChangeEnd: (value) async {
                    final SharedPreferences prefs =
                        await SharedPreferences.getInstance();
                    prefs.setDouble('fontSize', fontSize);
                  },
                ),
              ),
            ],
          ),
          const SizedBox(height: 50),
          Container(
            padding: const EdgeInsets.all(20),
            color: Colors.blue.shade100,
            child: Text(
              'Hola Mundo',
              style: Theme.of(context).textTheme.bodyLarge?.copyWith(
                    fontWeight: boldText ? FontWeight.bold : FontWeight.normal,
                    fontSize: fontSize,
                  ),
            ),
          ),
        ],
      ),
    );
  }
}