import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  final _formKey = GlobalKey();
  bool _loggedIn = false;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(),
        body: _loggedIn
            ? Center(
                child: RaisedButton(
                child: Text('logout'),
                onPressed: _logMeOut,
              ))
            : AutofillGroup(
                child: Form(
                  key: _formKey,
                  child: Padding(
                    padding: const EdgeInsets.all(8.0),
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.stretch,
                      children: <Widget>[
                        TextFormField(
                          decoration: InputDecoration(labelText: "Username"),
                          textInputAction: TextInputAction.next,
                          autofillHints: [AutofillHints.username],
                        ),
                        SizedBox(height: 8),
                        TextFormField(
                          decoration: InputDecoration(labelText: "Password"),
                          obscureText: true,
                          textInputAction: TextInputAction.done,
                          autofillHints: [AutofillHints.password],
                          onEditingComplete: _logMeIn,
                        ),
                        SizedBox(height: 8),
                        RaisedButton(
                          child: Text("login"),
                          onPressed: _logMeIn,
                        ),
                      ],
                    ),
                  ),
                ),
              ),
      ),
    );
  }

  _logMeIn() {
    setState(() {
      _loggedIn = true;
    });
  }

  _logMeOut() {
    setState(() {
      _loggedIn = false;
    });
  }
}