Arduino bluetooth demo - Flutter app entry point

main.dart

import 'package:flutter/material.dart';
import 'dart:async';
import 'bt-controller.dart';

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

class ArduinoBT extends StatelessWidget {

    @override
    Widget build(BuildContext context) {

        return MaterialApp(
            title: 'Arduino BT Demo',
            theme: ThemeData(primarySwatch: Colors.deepPurple),
            home: MainPage(title: 'Arduino BT Demo'),
        );
    }
}

class MainPage extends StatefulWidget {

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

    final String title;

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

class _MainPageState extends State<MainPage> {

    String sensorValue = "N/A";
    bool ledState = false;

    @override
    initState() {
        
        super.initState();
        BTController.init(onData);
        scanDevices();
    }

    void onData(dynamic str) { setState(() { sensorValue = str; }); }

    void switchLed() {

        setState(() { ledState = !ledState; });
        BTController.transmit(ledState ? '0' : '1');
    }

    Future<void> scanDevices() async {

        BTController.enumerateDevices()
            .then((devices) { onGetDevices(devices); });
    }

    void onGetDevices(List<dynamic> devices) {

        Iterable<SimpleDialogOption> options = devices.map((device) {

            return SimpleDialogOption(
                child: Text(device.keys.first),
                onPressed: () { selectDevice(device.values.first); },
            );
        });

        SimpleDialog dialog = SimpleDialog(
            title: const Text('Choose a device'),
            children: options.toList(),
        );

        showDialog(
            barrierDismissible: false,
            context: context,
            builder: (BuildContext context) { return dialog; }
        );
    }

    selectDevice(String deviceAddress) {

        Navigator.of(context, rootNavigator: true).pop('dialog');
        BTController.connect(deviceAddress);
    }
    
    @override
    Widget build(BuildContext context) {

        Color color = ledState ? Colors.deepPurpleAccent : Colors.white24;
        TextTheme theme = Theme.of(context).textTheme;

        return Scaffold(
            appBar: AppBar(title: Text(widget.title)),
            body: Container(
                decoration: BoxDecoration(color: Colors.black),
                  child: Center(
                      child: Column(
                        mainAxisAlignment: MainAxisAlignment.center,
                        children: <Widget>[
                            Text('Sensor Value', style: theme.display1.copyWith(color: Colors.white)),
                            Text(sensorValue, style: theme.display2.copyWith(color: Colors.white)),
                        ],
                    )

                  ),
            ),
            floatingActionButton: FloatingActionButton(
                backgroundColor: color,
                onPressed: switchLed,
                tooltip: 'Increment',
                child: Icon(Icons.power_settings_new),
            ), 
        );
    }
}