The classic Flutter incrementer app with added SnackBar

incrementer_snackbar.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Snackbars',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Snackbars'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;

  @override
  createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() => setState(() => _counter++);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      // The button is wrapped in a Builder as Scaffold.of(context) cannot
      // be called in the same build function that creates the Scaffold.
      floatingActionButton: Builder(
        builder: (context) => FloatingActionButton(
              onPressed: () {
                _incrementCounter();
                Scaffold.of(context).showSnackBar(SnackBar(
                      content: Text('Counter is now $_counter'),
                    ));
              },
              tooltip: 'Increment',
              child: Icon(Icons.add),
            ),
      ),
    );
  }
}