flutter_login_form

login.dart

import 'package:flutter/material.dart';

class Login extends StatefulWidget {
  @override
  _LoginState createState() => _LoginState();
}

class _LoginState extends State<Login> {
  String _email;
  String _password;

  final _loginFormKey = GlobalKey<FormState>();
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Form(
        key: _loginFormKey,
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            // Email
            TextFormField(
              validator: (val) {
                if (val.isEmpty) {
                  return 'You must enter a valid email!';
                }
                return null;
              },
              onSaved: (val) => _email = val,
            ),
            // Password
            TextFormField(
              obscureText: true,
              validator: (val) {
                if (val.isEmpty) {
                  return 'You must enter a valid password!';
                }
                return null;
              },
              onSaved: (val) => _email = val,
            ),
            // Login button.
            RaisedButton(
              child: Text('Login'),
              onPressed: () {
                if (_loginFormKey.currentState.validate()) {
                  _loginFormKey.currentState.save();
                  print('Email: $_email, password: $_password');
                }
              },
            ),
          ],
        ),
      ),
    ),
  }
}