Adaptive UI Talk: Example of handling light mode and dark mode in Material.

main.dart

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      darkTheme: ThemeData(brightness: Brightness.dark),
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Flutter Forward 2023'),
        ),
        body: const _MyPage(),
      ),
    );
  }
}

class _MyPage extends StatelessWidget {
  const _MyPage();

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Icon(
        Theme.of(context).brightness == Brightness.light
            ? Icons.light_mode
            : Icons.dark_mode,
        size: 100.0,
      ),
    );
  }
}