Flutter: Demo login page

loginPage.dart

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),
      home: TextFieldFocusExample(),
    );
  }
}

class TextFieldFocusExample extends StatefulWidget {
  @override
  State createState() => TextFieldFocusExampleState();
}

class TextFieldFocusExampleState extends State<TextFieldFocusExample> {
  TextEditingController _emailController,_pwController;
  FocusNode _emailFocus,_pwFocus;

  // Initially password is obscure
  bool _obscureText = true;
  String _password;
  String _email;

  bool isValidEmail() {
    if ((_email == null) || (_email.length == 0)) {
      return true;
    }
    return RegExp(r"^[a-zA-Z0-9.a-zA-Z0-9.!#$%&'*+-/=?^_`{|}~]+@[a-zA-Z0-9]+\.[a-zA-Z]+").hasMatch(_email);
  }

  bool isValidPassword() {
    if ((_password == null) || (_password.length == 0)) {
      return true;
    }
    return  (_password?.length > 6);
  }

  void _toggle() {
    setState(() {
      _obscureText = !_obscureText;
    });
  }

  void _validate() {
    setState(() {
      _email = _emailController.text;
      _password = _pwController.text;
    });
  }
  void performLogin() {
    //login here
  }

  @override
  void initState() {
    _emailController = TextEditingController();
    _pwController = TextEditingController();
    _emailFocus = FocusNode();
    _pwFocus = FocusNode();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {

    return Scaffold(
      body: SafeArea(
        child: ListView(
          children: <Widget>[
            const SizedBox(height: 80.0),
            Center(
              child: Text('Login',style: TextStyle(
                  fontSize: 32.0
              ),),
            ),
            const SizedBox(height: 80.0),
            Padding(
              padding: const EdgeInsets.all(16.0),
              child: Material(
                borderRadius: BorderRadius.circular(10.0),
                child: TextField(
                  focusNode: _emailFocus,
                  controller: _emailController,
                  obscureText: false,
                  keyboardType: TextInputType.emailAddress, //show email keyboard
                  textInputAction: TextInputAction.next,
                  onSubmitted: (input){
                    _emailFocus.unfocus();
                    _email = input;
                    FocusScope.of(context).requestFocus(_pwFocus);
                  },
                  onTap: _validate,
                  decoration: InputDecoration(
                    labelText: "Email",
                    hintText: 'Enter your password',
                    errorText: isValidEmail() ? null : "Invalid Email Address",
                  ),
                ),
              ),
            ),
            Padding(
              padding: const EdgeInsets.all(16.0),
              child: Material(
                borderRadius: BorderRadius.circular(10.0),
                child: TextField(
                  focusNode: _pwFocus,
                  controller: _pwController,
                  obscureText: _obscureText,
                  textInputAction: TextInputAction.done,
                  onSubmitted: (input){
                    _pwFocus.unfocus();
                    _password = input;
                    performLogin();
                  },
                  onTap: _validate,
                  decoration: InputDecoration(
                    labelText: "Password",
                    hintText: 'Enter your password',
                    errorText: isValidPassword() ? null : "Password too short.",
                    suffixIcon: IconButton(
                      icon: Icon(
                        _obscureText ? Icons.visibility : Icons.visibility_off,
                        color: Theme.of(context).primaryColorDark,
                      ),
                      onPressed: _toggle,
                    ),
                  ),
                ),
              ),
            ),
            const SizedBox(height: 40.0),
            ButtonBar(
              children: <Widget>[
                RaisedButton(onPressed: (){
                  performLogin();
                },child: Text('Login'),color: Colors.white)
              ],
            )
          ],
        ),
      ),
    );
  }
}