flutter_with_android_context.dart

import 'package:flutter/material.dart';

void main() => runApp(new MyApp()); // Application

class MyApp extends StatelessWidget { // MainActivity
  
  @override
  Widget build(BuildContext context) {  // onCreate
    return new MaterialApp(
      title: 'Flutter Demo',  // app_name
      theme: new ThemeData(   // AppTheme

        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Flutter Demo Home Page'),  // NavHost
    );
  }
}

class MyHomePage extends StatefulWidget { // Fragment

  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() {
    return new _MyHomePageState();  // setup MVP/MVVM
  }
}

class _MyHomePageState extends State<MyHomePage> {  // Presenter/ViewModel

  int _counter = 0;

  void _incrementCounter() {
    setState(() {   // invalidate(), render() (MVI)
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {

    return new Scaffold(  // CoordinatorLayout : appBar, body, fab

      appBar: new AppBar(
        title: new Text(widget.title),  // TextView
      ),

      body: new Center( // <center>child</center>

        child: new Column(  // LinearLayout with vertical orientation (horizontal: Row)

          mainAxisAlignment: MainAxisAlignment.center,

          children: <Widget>[
            new Text(
              'You have pushed the button this many times:',
            ),
            new Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: new FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: new Icon(Icons.send),
      ),
    );
  }
}