DeviceOrientation example

main.dart

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

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(context) => const MaterialApp(
        home: MyHomePage(),
      );
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({
    super.key,
  });

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

class _MyHomePageState extends State<MyHomePage> {
  late final ValueNotifier<DeviceOrientation> _valueNotifier;

  @override
  void initState() {
    _valueNotifier = ValueNotifier(DeviceOrientation.portraitUp)
      ..addListener(_listener);
    super.initState();
  }

  @override
  void dispose() {
    _valueNotifier
      ..removeListener(_listener)
      ..dispose();
    super.dispose();
  }

  void _next() {
    var next = DeviceOrientation.values.indexOf(_valueNotifier.value) + 1;
    if (!(next < DeviceOrientation.values.length)) {
      next = 0;
    }
    setState(() => _valueNotifier.value = DeviceOrientation.values[next]);
  }

  void _listener() => SystemChrome.setPreferredOrientations(
        [_valueNotifier.value],
      );

  @override
  Widget build(context) => Scaffold(
        body: Center(
          child: ValueListenableBuilder(
            valueListenable: _valueNotifier,
            builder: (context, orientation, _) => Text(orientation.name),
          ),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: _next,
          tooltip: 'next',
          child: const Icon(Icons.rotate_90_degrees_cw),
        ),
      );
}