MaterialBanner

import 'package:flutter/material.dart';

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

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

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        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);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("MaterialBanner"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            ElevatedButton(
                onPressed: () {
                  MaterialBanner materialBanner = MaterialBanner(
                    backgroundColor: Colors.amber,
                    leading: Icon(Icons.wallet_giftcard),
                    content: Text("I am new material banner"),
                    contentTextStyle: TextStyle(
                        color: Colors.black, fontWeight: FontWeight.bold),
                    actions: [
                      TextButton(
                          onPressed: () {
                            ScaffoldMessenger.of(context)
                                .hideCurrentMaterialBanner();
                          },
                          child: Text("Open")),
                      TextButton(
                          onPressed: () {
                            ScaffoldMessenger.of(context)
                                .hideCurrentMaterialBanner();
                          },
                          child: Text("Close"))
                    ],
                  );

                  ScaffoldMessenger.of(context)
                      .showMaterialBanner(materialBanner);
                },
                child: const Text('Show Banner'))
          ],
        ),
      ),
      // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}