Language Helper


Make it easier for you to implement multiple languages into your app with minimal effort.


  • Easy to control the language translations in your application. Automatically use the current device locale in the first open if possible.

  • You can completely control the translated text with LanguageConditions.

  • Supports analyzing which text is missing in specific language.

  • Supports analyzing which text is in your app but not in your language data and vice versa.

  • Supports extracting the needed text for translation from all the .dart files in your project with a single command dart run language_helper:generate (still in the early stages). Original package is language_helper_generator.


Create the data:

LanguageData data = {
  LanguageCodes.en: {
    'Hello @{text}, @number': 'Hello @{text}, @number',
    'Change language': 'Change language',
    'You have @{number} dollar': LanguageConditions(
      // Specify the param to use the conditions
      param: 'number',
      conditions: {
        '0': 'You have zero dollar',
        '1': 'You have @{number} dollar',

        // Return this when the is no condition satisfied
        'default': 'You have @{number} dollars',

    // This translation is wrong with the plural number so we need to override.
    'You have @{number} dollar in your wallet':
        'You have @{number} dollar in your wallet',
  }, {
    'Hello @{text}, @number': 'Xin Chào @{text}, @number',
    'Change language': 'Thay đổi ngôn ngữ',
    'You have @{number} dollar': 'Bạn có @{number} đô-la',

    // This translation is right so we don't need to override.
    'You have @{number} dollar in your wallet':
        'Bạn có @{number} đô-la trong ví của bạn',

With the LanguageConditions, you can completely control which text is returned according to the condition of the parameters.

Initialize the data:

final languageHelper = LanguageHelper.instance;

main() async {
  // LanguageHelper should be initialized before calling `runApp`.
  await languageHelper.initial(
      // This is [LanguageData] and it must be not empty.
      data: data,

      // [Optional] Default is set to the device locale (if available) or the first language of [data]
      initialCode: LanguageCodes.en,

      // [Optional] Change the app language when the device language is changed.
      syncWithDevice: true,

  runApp(const MyApp());

You can implement flutter localizations to your app like this

class App extends StatelessWidget {
  const App({super.key});

  Widget build(BuildContext context) {
    return LanguageBuilder(
      builder: (context) {
        return MaterialApp(
          localizationsDelegates: languageHelper.delegate,
          supportedLocales: languageHelper.locales,
          locale: languageHelper.locale,
          home: const HomePage(),

Change the language:


Add language data to the current data:


That methods have activate parameter which automaticaly rebuild all needed LanguageBuilder, so notice that you may get the setState issue because of the rebuilding of the LanguageBuilder when it's still building. If the error occurs, you may need to set it to false and activate the new data yourself by using reload method.

Get list of implemented LanguageCodess:

// List of [LanguageCodes] from the [data]
final codes =;

// List of [LanguageCodes] from the [dataOverrides]
final codesOverrides = languageHelper.codesOverrides;

// List of [LanguageCodes] from both of the [data] and [dataOverrides] without duplicated
final codesBoth = languageHelper.codesBoth;

Get text:

final translated = languageHelper.translate(
    'Hello @{text}, @number', 
    toCode: LanguageCodes.en, // [Optional] Translate to specific language code
    params {'text' : 'World', 'number': '10'}, // [Optional] Translate with parameters
// Hello World, 10

Use extension:

final translated = 'Hello'.tr;
final translatedParam = 'Hello @{text}, @number'.trP({'text': 'World', 'number': '10'});
final translatedTo = 'Hello @{text}, @number'.trT(LanguageCodes.en);
final translatedFull = 'Hello @{text}, @number'.trF(toCode: LanguageCodes.en, params: {'text': 'World', 'number': '10'});

Note: The ${param} works in all cases, the @param only work if the text ends with a white space, the end of a line, or the end of a new line.

Beside the onChanged method, you can listen to the language changed events by using stream:

final sub = => print(code));

Note: Remember to sub.cancel() when it's not in use to avoid memory leaks.

Use builder to rebuild the widgets automatically on change:

  • For all widget in your app:
Widget build(BuildContext context) {
  return LanguageBuilder(builder: (context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Hello'.tr),
        body: Center(
          child: Column(
            children: [
                onPressed: () {
                child: Text('Change language'.tr),
  • For specific widget:
    builder: (context) {
        return Text('Hello'.tr);
  • There is a short version of LanguageBuilder is Tr:
Tr((_) => Text('Hello'.tr)),

You can analyze the missing texts for all language with this function:


This function will be automatically called in initial when the isDebug is true.

Here is the result from the Example:

flutter: [Language Helper]
flutter: [Language Helper] ==================================================
flutter: [Language Helper]
flutter: [Language Helper] Analyze all languages to find the missing texts...
flutter: [Language Helper] Results:
flutter: [Language Helper]   LanguageCodes.en:
flutter: [Language Helper]     This text is missing in `en`
flutter: [Language Helper]
flutter: [Language Helper]
flutter: [Language Helper]     This text is missing in `vi`
flutter: [Language Helper]
flutter: [Language Helper] ==================================================
flutter: [Language Helper]


You can also create a base LanguageData by using command:

dart run language_helper:generate

If you want to change the generating path, using this:

dart run language_helper:generate --path=./example/lib

This command will also run dart format for the generated files, so you can easily manage the translations using the version control.

This runner will get all the texts that using language_helper extensions (.tr, .trP, .trT, .trF) and .translate method then creating a base structure for LanguageData. You can see the generated data in the example.

The data will be generated with this format:

|-- .lib
|   |--- resources
|   |    |--- language_helper
|   |    |    |--- _language_data_abstract.g.dart
|   |    |    |--- language_data.dart

LanguageData Serialization

Convert LanguageData to JSON:

final json = data.toJson();

Convert JSON to LanguageData:

final data = LanguageDataSerializer.fromJson(json);

Additional Information

  • The app will try to use the Devicelocale to set the initialCode if it is not set, if the Devicelocale is unavailable, it will use the first language in data insteads.

  • No matter how many LanguageBuilder that you use, the plugin only rebuilds the outest (the root) widget of LanguageBuilder, so it improves a lot of performances. And all LanguageBuilder widgets will be rebuilt at the same time. This setting can be changed with forceRebuild parameter in both initial for global setting and LanguageBuilder for local setting.

  • The LanguageCodes contains all the languages with additional information like name in English (englishName) and name in native language (nativeName).


As the project is currently in its early stages, it may contain bugs or other issues. Should you experience any problems, we kindly ask that you file an issue to let us know. Additionally, we welcome contributions in the form of pull requests (PRs) to help enhance the project.