Flutter Mobile Development · Lección

Shared Preferences para datos

Utilice `shared_preferences` para almacenar localmente pequeñas cantidades de datos, como ajustes y preferencias del usuario, en pares clave-valor.

Shared Preferences para datos es una lección gratuita de Flutter Mobile Development en CoddyKit. Esta es la lección 1 de 4. Puedes leer la lección completa abajo gratuitamente — luego la practicas en el navegador con un editor de código integrado y un tutor de IA 24/7. Forma parte de la ruta de aprendizaje de Flutter Mobile Development, y tu progreso se sincroniza en la web y la app de CoddyKit. El curso de Flutter Mobile Development incluye 4 lecciones en total.

Partes de esta lección aún no han sido traducidas y se muestran en inglés.

What are Shared Preferences?

When building mobile apps, you often need to store small bits of data locally on the device. This could be anything from a user's dark mode preference to their last logged-in status.

shared_preferences is a Flutter package that helps you do just that! It provides a simple way to store key-value pairs of primitive data types.

Why Use Shared Preferences?

Simple Data: Ideal for storing simple data types like booleans, integers, doubles, strings, and lists of strings.
User Settings: Perfect for saving user preferences, app settings, or theme choices.
Lightweight: It's a quick and easy way to persist small amounts of data without needing a full database.

Think of it like a small digital notepad for your app's temporary memory!

Installing the Package

To use shared_preferences, you first need to add it to your project's dependencies.

Open your pubspec.yaml file and add the following line under dependencies:

dependencies:
  flutter:
    sdk: flutter
  shared_preferences: ^2.2.2 # Add this line

Saving Your First Preference

Once the package is added, you can start saving data. You'll need to get an instance of SharedPreferences and then use methods like setBool(), setString(), etc.

Remember to use await because these operations are asynchronous!

import 'package:shared_preferences/shared_preferences.dart';

Future<void> saveSetting() async {
  SharedPreferences prefs = await SharedPreferences.getInstance();
  await prefs.setBool('isDarkMode', true);
  print('Dark mode setting saved!');
}

Run It: Saving a Boolean

Try running this example to see how a boolean value is saved. We'll set a 'welcomeShown' flag to true.

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

void main() async {
  WidgetsFlutterBinding.ensureInitialized(); 
  SharedPreferences prefs = await SharedPreferences.getInstance();

  // Save a boolean value
  await prefs.setBool('welcomeShown', true);
  print('welcomeShown saved: ${prefs.getBool('welcomeShown')}');
}

Retrieving Saved Data

To get data back, you use corresponding get methods like getBool(), getString(), etc. These methods return a nullable type (e.g., bool?) because the key might not exist.

It's good practice to provide a default value using the ?? operator if the key is not found.

import 'package:shared_preferences/shared_preferences.dart';

Future<bool> getSetting() async {
  SharedPreferences prefs = await SharedPreferences.getInstance();
  // Get 'isDarkMode', default to false if not found
  bool isDark = prefs.getBool('isDarkMode') ?? false;
  return isDark;
}

Run It: Loading a Boolean

Let's load the welcomeShown preference we saved earlier. Notice how we handle the case where it might not exist by providing a default of false.

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

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  SharedPreferences prefs = await SharedPreferences.getInstance();

  // Load 'welcomeShown', default to false if not present
  bool welcomeShown = prefs.getBool('welcomeShown') ?? false;
  print('Is welcome screen already shown? $welcomeShown');

  // Let's try to load a key that doesn't exist
  String? userName = prefs.getString('userName');
  print('User Name: ${userName ?? 'Guest'}');
}

Saving Other Data Types

shared_preferences supports several basic data types:

setString(key, value) for text
setInt(key, value) for whole numbers
setDouble(key, value) for decimal numbers
setStringList(key, value) for lists of strings

There are corresponding get methods for each type.

Run It: Saving Mixed Data

This example demonstrates saving and loading a string, an integer, and a list of strings. See how different types are handled.

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

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  SharedPreferences prefs = await SharedPreferences.getInstance();

  // Save different data types
  await prefs.setString('userName', 'Coddy');
  await prefs.setInt('score', 12345);
  await prefs.setStringList('favoriteFoods', ['Pizza', 'Sushi', 'Tacos']);
  print('All data saved!');

  // Load and print them
  String? name = prefs.getString('userName');
  int? score = prefs.getInt('score');
  List<String>? foods = prefs.getStringList('favoriteFoods');

  print('User Name: ${name ?? 'N/A'}');
  print('Score: ${score ?? 0}');
  print('Favorite Foods: ${foods ?? []}');
}

Deleting Preferences

You can also remove stored preferences:

remove(key): Deletes a specific key-value pair.
clear(): Deletes ALL data stored by your app using shared_preferences. Use with caution!

Both methods are asynchronous and return a Future<bool> indicating success.

Quick Check

You want to store a user's preferred language, which is a single string like 'en_US' or 'es_ES'. Which shared_preferences method is the most appropriate for saving this data?

Recap & Next Steps

Great job! You've learned how to use shared_preferences to store and retrieve small, simple data locally in your Flutter applications.

It's ideal for user settings and preferences.
Supports basic types: bool, int, double, string, and List<String>.
Operations are asynchronous (use await).
Remember to handle null values when retrieving data.

Next, you'll explore more structured data storage with SQLite databases!

Preguntas frecuentes

¿La lección «Shared Preferences para datos» es gratis?

Sí — el texto completo de «Shared Preferences para datos» es gratis para leer aquí en la web. Para practicarla de forma interactiva (editor de código integrado y tutor de IA 24/7) y desbloquear el resto del curso de Flutter Mobile Development, actualiza a CoddyKit PRO. El curso de Flutter Mobile Development incluye 4 lecciones en total.

¿Qué aprenderé en «Shared Preferences para datos»?

Utilice `shared_preferences` para almacenar localmente pequeñas cantidades de datos, como ajustes y preferencias del usuario, en pares clave-valor. Practicas Flutter Mobile Development con código real que ejecutas directamente en el navegador, y un tutor de IA 24/7 responde tus preguntas mientras trabajas en la lección.

¿Necesito experiencia previa para empezar Flutter Mobile Development?

No se requiere experiencia previa. Flutter Mobile Development en CoddyKit está estructurado para principiantes hasta estudiantes avanzados, así que puedes empezar aquí o desde el inicio y avanzar a tu ritmo. Esta es la lección 1 de 4.

¿Cuánto tiempo toma la lección «Shared Preferences para datos»?

La mayoría de las lecciones de CoddyKit toman alrededor de 5–10 minutos. Cada una es compacta e interactiva, así que avanzas constantemente y retomas exactamente por donde dejaste en la web y la app.

¿Puedo escribir y ejecutar código en esta lección de Flutter Mobile Development?

Sí. Cada lección de Flutter Mobile Development incluye un editor de código integrado, así que escribes y ejecutas código real directamente en tu navegador y obtienes retroalimentación instantánea de IA — sin configuración local necesaria.

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