How To Create Dynamic Light And dark Theme In Flutter App

dependencies:
  flutter:
    sdk: flutter

  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^0.1.2
  dynamic_theme: ^1.0.0

flutter pub get

import 'package:dynamic_theme/dynamic_theme.dart';
import 'package:dynamic_theme/theme_switcher_widgets.dart';

import 'package:dynamic_theme/dynamic_theme.dart';
import 'package:dynamic_theme/theme_switcher_widgets.dart';
import 'package:flutter/material.dart';


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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return DynamicTheme(
        defaultBrightness: Brightness.light,
        data: (brightness) => ThemeData(
          primarySwatch: Colors.indigo,
          brightness: brightness,
        ),
        themedWidgetBuilder: (context, theme) {
          return MaterialApp(
            debugShowCheckedModeBanner: false,
            title: 'Flutter Demo',
            theme: theme,
            home: MyHomePage(),
          );
        });
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        centerTitle: true,
        title: Text("Light & Dark Theme"),

      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            RaisedButton(
              color: Colors.indigo,
              onPressed: changeBrightness,
              child: const Text("Change Brightness",style: TextStyle(color: Colors.white),),
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: showChooser,
        child: const Icon(Icons.add),
      ),
      bottomNavigationBar: BottomNavigationBar(
        items: [
          BottomNavigationBarItem(
              icon: Icon(Icons.insert_drive_file), title: Text("File")),
          BottomNavigationBarItem(
              icon: Icon(Icons.show_chart), title: Text("Chart")),
        ],
      ),
    );
  }

  void showChooser() {
    showDialog<void>(
        context: context,
        builder: (context) {
          return BrightnessSwitcherDialog(
            onSelectedTheme: (brightness) {
              DynamicTheme.of(context).setBrightness(brightness);
            },
          );
        });
  }

  void changeBrightness() {
    DynamicTheme.of(context).setBrightness(
        Theme.of(context).brightness == Brightness.dark
            ? Brightness.light
            : Brightness.dark);
  }

  void changeColor() {
    DynamicTheme.of(context).setThemeData(ThemeData(
        primaryColor: Theme.of(context).primaryColor == Colors.indigo ? Colors.red : Colors.indigo));
  }
}