class TestWidget extends StatelessWidget {
  final _formKey = GlobalKey<FormState>();
  TestWidget({Key? key}) : super(key: key);
  
  @override
  Widget build(BuildContext context) {
    return Form(
      key: _formKey,
      child: Column(
        children: [
          ElevatedButton(
            onPressed: (){
              _formKey.currentState?.reset();
            },
            child: const Text("reset")
          ),
          TextFormField(
            onChanged: (value) {
              // not executed on _formKey.currentState?.reset()
              print(value);
            }
          )
        ],
      )
    );
  }
}