This string_extractor_intl package extracts hardcoded strings from your Flutter project and generates ARB files (app_en.arb) for internationalization and localization. It is really helpful if you are already deep in your project and need localization.
Generate app_en.arb and use replace strings with AppLocalizations.of(context).something in your project manually. Then translate the en file to other languages. The --replace tag has some issues, which is supposed to replace all the strings with AppLocalizations.of(context).something for you.