Flutter localization without context

If you would prefer to not use a package then here is a solution that worked for me. Now the most common implementation of AppLocalizations I’ve seen usually has these two lines:

//.........
static const LocalizationsDelegate<AppLocalizations> delegate =
      _AppLocalizationsDelegate();

static AppLocalizations of(BuildContext context) {
  return Localizations.of<AppLocalizations>(context, AppLocalizations);
}
//.........

The implementation of the delegate would look something like this:

class _AppLocalizationsDelegate extends LocalizationsDelegate<AppLocalizations> {
  const _AppLocalizationsDelegate();

  @override
  Future<AppLocalizations> load(Locale locale) async {
    AppLocalizations localizations = new AppLocalizations(locale);
    await localizations.load();

    return localizations;
  }

  //... the rest omitted for brevity
}

Notice the load method on the delegate returns a Future<AppLocalizations>. The load method is usually called once from main and never again so you can take advantage of that by adding a static instance of AppLocalizations to the delegate. So now your delegate would look like this:

class _AppLocalizationsDelegate extends LocalizationsDelegate<AppLocalizations> {
  const _AppLocalizationsDelegate();

  static AppLocalizations instance;

  @override
  Future<AppLocalizations> load(Locale locale) async {
    AppLocalizations localizations = new AppLocalizations(locale);
    await localizations.load();

    instance = localizations; // set the static instance here

    return localizations;
  }

  //... the rest omitted for brevity
}

Then on your AppLocalizations class you would now have:

//.........
static const LocalizationsDelegate<AppLocalizations> delegate =
      _AppLocalizationsDelegate();

static AppLocalizations of(BuildContext context) {
  return Localizations.of<AppLocalizations>(context, AppLocalizations);
}

static AppLocalizations get instance => _AppLocalizationsDelegate.instance; // add this
//.........

Now in your translate helper method you could have:

String tr(String key) {
    return AppLocalizations.instance.translate(key);
}

No context needed.