example

Run in terminal : flutter pub run modified_localization:generate -o locale_keys.g.dart --source-dir /your_dir

example/resources/langs/en-EN.json

{
  "hi": "Hi !",
  "welcome": "Welcome {}"
}

Will be generated strings class like this, then you can use it without .tr(), if arguments needed will be generated args function

abstract class Strings {
  static String get hi => 'hi'.tr();

  static String welcome(String arg0) {
    return 'welcome'.tr(args: [arg0]);
  }
}

example/lib/main.dart

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: [
            Text(Strings.hi),
            Text(Strings.welcome("Flutter")),
          ],
        ),
        alignment: Alignment.center,
      ),
    );
  }
}