Main file for AFE_Flutter module.

main.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: 'AFE Flutter',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or press Run > Flutter Hot Reload in a Flutter IDE). Notice that the
        // counter didn't reset back to zero; the application is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'AFE Flutter Module'),
    );
  }
}

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

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  String dropdownValue = 'Add';
  int result = 0;

  _addNumbers(int n1, int n2) {
    return n1 + n2;
  }

  _multiplyNumbers(int n1, int n2) {
    return n1 * n2;
  }

  _setResults(int n1, int n2) {
    setState(() {
      if (dropdownValue == 'Add') {
        result = _addNumbers(n1, n2);
      } else {
        result = _multiplyNumbers(n1, n2);
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
        appBar: AppBar(
          // Here we take the value from the MyHomePage object that was created by
          // the App.build method, and use it to set our appbar title.
          title: Text(widget.title),
        ),
        body: Center(
          // Center is a layout widget. It takes a single child and positions it
          // in the middle of the parent.
          child: Column(
            // Column is also layout widget. It takes a list of children and
            // arranges them vertically. By default, it sizes itself to fit its
            // children horizontally, and tries to be as tall as its parent.
            //
            // Invoke "debug painting" (press "p" in the console, choose the
            // "Toggle Debug Paint" action from the Flutter Inspector in Android
            // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
            // to see the wireframe for each widget.
            //
            // Column has various properties to control how it sizes itself and
            // how it positions its children. Here we use mainAxisAlignment to
            // center the children vertically; the main axis here is the vertical
            // axis because Columns are vertical (the cross axis would be
            // horizontal).
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Container(
                  padding: EdgeInsets.all(10),
                  child: Row(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: <Widget>[
                        Text('First Number: ',
                            style:
                                TextStyle(color: Colors.black, fontSize: 16)),
                        Text('10',
                            style: TextStyle(color: Colors.blue, fontSize: 16)),
                      ])),
              Container(
                  padding: EdgeInsets.all(10),
                  child: Row(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: <Widget>[
                        Text('Second Number: ',
                            style:
                                TextStyle(color: Colors.black, fontSize: 16)),
                        Text('20',
                            style: TextStyle(color: Colors.blue, fontSize: 16)),
                      ])),
              Container(
                  margin: EdgeInsets.all(10),
                  child: Row(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: <Widget>[
                      DropdownButton<String>(
                        value: dropdownValue,
                        style: TextStyle(color: Colors.blue, fontSize: 16),
                        items: <String>['Add', 'Multiply']
                            .map<DropdownMenuItem<String>>((String value) {
                          return DropdownMenuItem<String>(
                            value: value,
                            child: Text(value),
                          );
                        }).toList(),
                        onChanged: (String newValue) {
                          setState(() {
                            dropdownValue = newValue;
                          });
                        },
                      )
                    ],
                  )),
              RaisedButton(
                onPressed: () {
                  _setResults(10, 20);
                  _sendResultsToAndroidiOS();
                },
                textColor: Colors.white,
                padding: const EdgeInsets.all(0.0),
                child: Container(
                    decoration: BoxDecoration(color: Colors.blue),
                    padding: const EdgeInsets.all(10.0),
                    child: const Text('Send Results to Android/iOS module',
                        style: TextStyle(fontSize: 16))),
              ),
              Container(
                  margin: EdgeInsets.all(10),
                  child: Text(
                    'Result: $result',
                    style: TextStyle(color: Colors.blue, fontSize: 16),
                  ))
            ],
          ),
        ));
  }

  void _sendResultsToAndroidiOS() {
    //TODO send results to Android/iOS module
  }
}