sample for nir orientation

main.dart

/// in puspec dependency: native_device_orientation: ^1.1.4
  
// sample for nir.

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:native_device_orientation/native_device_orientation.dart';

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  SystemChrome.setPreferredOrientations(
    [DeviceOrientation.portraitUp, DeviceOrientation.portraitDown],
  );
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  bool landscape = false;
  int quarterTurns = 0;

  final turnsByOrientation = <NativeDeviceOrientation, int>{
    NativeDeviceOrientation.landscapeRight: 3,
    NativeDeviceOrientation.landscapeLeft: 1,
    NativeDeviceOrientation.portraitDown: 2,
    NativeDeviceOrientation.portraitUp: 0,
    NativeDeviceOrientation.unknown: 0,
  };

  final deviceOrientator = NativeDeviceOrientationCommunicator();
  late StreamSubscription sub;

  @override
  void initState() {
    sub = deviceOrientator.onOrientationChanged(useSensor: true).listen((data) {
      quarterTurns = turnsByOrientation[data] ?? 0;
      print('Orientation: $data');
      setState(() {});
    });
    super.initState();
  }

  @override
  void dispose() {
    sub.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return RealHome(
      turns: quarterTurns,
    );
  }
}

class RealHome extends StatefulWidget {
  final int turns;

  const RealHome({Key? key, required this.turns}) : super(key: key);

  @override
  State<RealHome> createState() => _RealHomeState();
}

class _RealHomeState extends State<RealHome> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('is Landscape: ${widget.turns}'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text('You have pushed the button this many times:'),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
            RotatedBox(
              quarterTurns: widget.turns,
              child: Text('Text always straight'),
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ),
    );
  }

  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }
}