Theme (Light and Dark) in Flutter

 import "package:flutter/material.dart";

import "package:sdreatech_learning_widget/Theme/themes.dart";

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

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

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  void initState() {
    super.initState();
    currentTheme.addListener(() {
      setState(() {});
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "Theme",
      debugShowCheckedModeBanner: false,
      theme: CustomTheme.lightTheme,
      darkTheme: CustomTheme.darkTheme,
      themeMode: currentTheme.currentTheme,
      home: const ThemePracticeTutorial(),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.blue,
        title: const Text(
          "Theme Practice",
          style: TextStyle(fontWeight: FontWeight.bold, color: Colors.white),
        ),
        centerTitle: true,
        actions: [
          IconButton(
            onPressed: () {
              currentTheme.toggleTheme();
            },
            icon: const Icon(Icons.brightness_4_rounded, color: Colors.white),
          ),
        ],
      ),
      body: const Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              "Flutter Themes Demo",
              style: TextStyle(fontWeight: FontWeight.bold, fontSize: 30.0),
            ),
          ],
        ),
      ),
    );
  }
}

import "package:flutter/material.dart";

CustomTheme currentTheme = CustomTheme();

class CustomTheme extends ChangeNotifier {
  static bool _isDarkTheme = false;

  ThemeMode get currentTheme {
    return _isDarkTheme ? ThemeMode.dark : ThemeMode.light;
  }

  void toggleTheme() {
    _isDarkTheme = !_isDarkTheme;
    notifyListeners();
  }

  static ThemeData get lightTheme {
    return ThemeData(
      primaryColor: Colors.lightBlue,
      scaffoldBackgroundColor: Colors.white,
      textTheme: const TextTheme(
        displayLarge: TextStyle(color: Colors.black),
        displayMedium: TextStyle(color: Colors.black),
        bodyLarge: TextStyle(color: Colors.black),
        bodyMedium: TextStyle(color: Colors.black),
      ),
    );
  }

  static ThemeData get darkTheme {
    return ThemeData(
      primaryColor: Colors.black,
      scaffoldBackgroundColor: Colors.black,
      textTheme: const TextTheme(
        displayLarge: TextStyle(color: Colors.white),
        displayMedium: TextStyle(color: Colors.white),
        bodyLarge: TextStyle(color: Colors.white),
        bodyMedium: TextStyle(color: Colors.white),
      ),
    );
  }
}