How to Add Localization Support in Flutter Packages

Oct 13, 2025 by wbrum.org 142 views

Introduction

As a developer, you may have encountered situations where you need to create a Flutter package that supports multiple languages or locales. This is where localization and internationalization come into play. In this article, we will explore how to add localization support inside Flutter packages.

What is Localization and Internationalization?

Localization and internationalization are two related but distinct concepts.

Localization refers to the process of adapting a product or service to a specific language, culture, or region. It involves translating text, formatting dates and numbers, and adapting the user interface to meet the needs of a particular market.
Internationalization, on the other hand, refers to the process of designing a product or service to be usable in multiple languages and cultures. It involves separating the code that deals with language and culture from the rest of the code, making it easier to adapt the product or service to different markets.

Why is Localization Important in Flutter Packages?

Localization is essential in Flutter packages because it allows consumers to use your package in their preferred language. This is particularly important for packages that contain text, such as labels, buttons, and error messages. By supporting multiple languages, you can make your package more accessible and user-friendly to a wider audience.

How to Add Localization Support in Flutter Packages

To add localization support in Flutter packages, you can follow these steps:

Step 1: Choose a Localization Library

There are several localization libraries available for Flutter, including:

flutter_localizations: This is the official localization library for Flutter. It provides a set of pre-built widgets and utilities for handling localization.
intl: This library provides a set of internationalization utilities, including date and number formatting, and text translation.
easy_localization: This library provides a simple and easy-to-use API for handling localization.

For this example, we will use the flutter_localizations library.

Step 2: Create a Localization File

To create a localization file, you need to create a new file in the lib/l10n directory of your package. The file should have a name that ends with _l10n.dart, such as messages_l10n.dart.

// lib/l10n/messages_l10n.dart
import 'package:flutter/material.dart';
import 'package:flutter_localizations/flutter_localizations.dart';
class MessagesLocalizations 
static const _localizedValues = {
'en' {
'hello': 'Hello',
'goodbye': 'Goodbye',
,
'fr': 
'hello' 'Bonjour',
'goodbye': 'Au revoir',
,
};
static Locale _locale;
static Locale get locale => _locale;
static void set locale(Locale locale) {
_locale = locale;
}
static String get hello => _localizedValues[_locale.languageCode]['hello'];
static String get goodbye => _localizedValues[_locale.languageCode]['goodbye'];
}

Step 3: Create a Localization Delegate

To create a localization delegate, you need to create a new class that extends the LocalizationsDelegate class. This class should override the build method to return a new instance of the MessagesLocalizations class.

// lib/l10n/messages_localizations_delegate.dart
import 'package:flutter/material.dart';
import 'package:flutter_localizations/flutter_localizations.dart';
import 'messages_l10n.dart';
class MessagesLocalizationsDelegate extends LocalizationsDelegate<MessagesLocalizations> {
@override
bool isSupported(Locale locale) => _localizedValues.containsKey(locale.languageCode);
@override
Future<MessagesLocalizations> load(Locale locale) => SynchronousFuture<MessagesLocalizations>(MessagesLocalizations(locale));
@override
bool shouldReload(MessagesLocalizationsDelegate oldDelegate) => false;
}

Step 4: Register the Localization Delegate

To register the localization delegate, you need to add the following code to the MaterialApp widget in your package's main function.

// lib/main.dart
import 'package:flutter/material.dart';
import 'package:flutter_localizations/flutter_localizations.dart';
import 'l10n/messages_localizations_delegate.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget 
@override
Widget build(BuildContext context) {
return MaterialApp(
localizationsDelegates [
MessagesLocalizationsDelegate(),
GlobalMaterialLocalizations.delegate,
GlobalWidgetsLocalizations.delegate,
],
supportedLocales: [
Locale('en', 'US'),
Locale('fr', 'FR'),
],
home: MyHomePage(),
);

}

Step 5: Use the Localization Delegate

To use the localization delegate, you need to create a new instance of the MessagesLocalizations class and call the set locale method to set the locale.

// lib/my_home_page.dart
import 'package:flutter/material.dart';
import 'l10n/messages_localizations.dart';
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> 
@override
Widget build(BuildContext context) {
return Scaffold(
appBar AppBar(
title: Text(MessagesLocalizations.of(context).hello),
),
body: Center(
child: Text(MessagesLocalizations.of(context).goodbye),
),
);

}

Conclusion

Adding localization support to Flutter packages is a straightforward process that involves choosing a localization library, creating a localization file, creating a localization delegate, registering the localization delegate, and using the localization delegate. By following these steps, you can make your package more accessible and user-friendly to a wider audience.

Example Use Cases

Here are some example use cases for adding localization support to Flutter packages:

Language support: By supporting multiple languages, you can make your package more accessible to users who speak different languages.
Regional support: By supporting different regions, you can make your package more relevant to users who live in different parts of the world.
Cultural support: By supporting different cultures, you can make your package more relevant to users who have different cultural backgrounds.

Best Practices

Here are some best practices for adding localization support to Flutter packages:

Use a localization library: Using a localization library can make it easier to add localization support to your package.
Create a localization file: Creating a localization file can make it easier to manage translations and formatting.
Use a localization delegate: Using a localization delegate can make it easier to handle localization in your package.
Test your package: Testing your package with different locales and languages can help you identify any issues with localization.

Conclusion

Q: What is the best way to add localization support to a Flutter package?

A: The best way to add localization support to a Flutter package is to use a localization library such as flutter_localizations. This library provides a set of pre-built widgets and utilities for handling localization.

Q: How do I choose the right localization library for my Flutter package?

A: When choosing a localization library for your Flutter package, consider the following factors:

Ease of use: Choose a library that is easy to use and has a simple API.
Features: Choose a library that provides the features you need, such as text translation and date formatting.
Community support: Choose a library that has a large and active community, which can provide support and help with any issues you may encounter.

Q: What is the difference between localization and internationalization?

A: Localization refers to the process of adapting a product or service to a specific language, culture, or region. It involves translating text, formatting dates and numbers, and adapting the user interface to meet the needs of a particular market.

Internationalization, on the other hand, refers to the process of designing a product or service to be usable in multiple languages and cultures. It involves separating the code that deals with language and culture from the rest of the code, making it easier to adapt the product or service to different markets.

Q: How do I create a localization file for my Flutter package?

A: To create a localization file for your Flutter package, follow these steps:

Create a new file in the lib/l10n directory of your package.
Name the file with a name that ends with _l10n.dart, such as messages_l10n.dart.
Import the flutter_localizations library and create a new class that extends the LocalizationsDelegate class.
Override the build method to return a new instance of the MessagesLocalizations class.
Create a new instance of the MessagesLocalizations class and call the set locale method to set the locale.

Q: How do I register the localization delegate in my Flutter package?

A: To register the localization delegate in your Flutter package, follow these steps:

Add the following code to the MaterialApp widget in your package's main function:

localizationsDelegates: [ MessagesLocalizationsDelegate(), GlobalMaterialLocalizations.delegate, GlobalWidgetsLocalizations.delegate, ],

2.  Add the following code to the `supportedLocales` property of the `MaterialApp` widget:
    ```dart
supportedLocales: [
  Locale('en', 'US'),
  Locale('fr', 'FR'),
],

Q: How do I use the localization delegate in my Flutter package?

A: To use the localization delegate in your Flutter package, follow these steps:

Create a new instance of the MessagesLocalizations class.
Call the set locale method to set the locale.
Use the MessagesLocalizations class to get the translated text and formatted dates and numbers.

Q: What are some best practices for adding localization support to a Flutter package?

A: Here are some best practices for adding localization support to a Flutter package:

Use a localization library: Using a localization library can make it easier to add localization support to your package.
Create a localization file: Creating a localization file can make it easier to manage translations and formatting.
Use a localization delegate: Using a localization delegate can make it easier to handle localization in your package.
Test your package: Testing your package with different locales and languages can help you identify any issues with localization.

Q: What are some common issues that can occur when adding localization support to a Flutter package?

A: Here are some common issues that can occur when adding localization support to a Flutter package:

Translation issues: Translations may not be accurate or up-to-date.
Formatting issues: Dates and numbers may not be formatted correctly.
Localization delegate issues: The localization delegate may not be registered correctly or may not be handling localization correctly.

Q: How can I troubleshoot issues with localization support in my Flutter package?

A: Here are some steps you can take to troubleshoot issues with localization support in your Flutter package:

Check the localization library documentation for any issues or known problems.
Check the localization file for any errors or issues.
Check the localization delegate for any errors or issues.
Test your package with different locales and languages to identify any issues.
Use a debugging tool to identify any issues with the localization support.