FlutterForm

import 'package:flutter/material.dart';
import 'package:form/form.dart';

class MyForm extends StatefulWidget {
  @override
  _MyFormState createState() => _MyFormState();
}

class _MyFormState extends State<MyForm> {
  final _formKey = GlobalKey<FormState>();
  String _inputText;

  @override
  Widget build(BuildContext context) {
    return Form(
      key: _formKey,
      child: Column(
        children: <Widget>[
          TextFormField(
            decoration: InputDecoration(labelText: 'Enter your name'),
            validator: (value) {
              if (value.isEmpty) {
                return 'Please enter your name';
              }
              return null;
            },
            onSaved: (value) => _inputText = value,
          ),
          RaisedButton(
            onPressed: () {
              if (_formKey.currentState.validate()) {
                _formKey.currentState.save();
                Scaffold.of(context).showSnackBar(
                  SnackBar(content: Text('Hello, $_inputText!'))
                );
              }
            },
            child: Text('Submit'),
          ),
        ],
      ),
    );
  }
}