Drop down menu in flutter

On Flutter.dev website, you can find this drop-down experience.

How to design such drop-down menu?

I have tried following but doesn't give the similar experience.

PopupMenuButton(
  child: Container(
    margin: const EdgeInsets.all(10),
    child: const Text(
      'Main menu',
      style: TextStyle(
        fontSize: 16,
        color: Colors.white,
        decoration: TextDecoration.underline,
      ),
    ),
  ),
  itemBuilder: (context) => [
    PopupMenuItem(
      child: const Text('Child one'),
      value: 1,
      onTap: () {},
    ),
    PopupMenuItem(
      child: const Text('Child two'),
      value: 1,
      onTap: () {},
    ),
  ],
)

Above code gives following experience.

You can use this widget drop-down button : https://pub.dev/packages/dropdown_button2

or you can refere to this code.

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter DropDownButton',
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),
      home: const MyHomePage(),
      debugShowCheckedModeBanner: false,
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

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

class _MyHomePageState extends State<MyHomePage> {

// Initial Selected Value
  String dropdownvalue = 'Item 1';

// List of items in our dropdown menu
  var items = [
    'Item 1',
    'Item 2',
    'Item 3',
    'Item 4',
    'Item 5',
  ];
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("Geeksforgeeks"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            DropdownButton(

              // Initial Value
              value: dropdownvalue,

              // Down Arrow Icon
              icon: const Icon(Icons.keyboard_arrow_down),

              // Array list of items
              items: items.map((String items) {
                return DropdownMenuItem(
                  value: items,
                  child: Text(items),
                );
              }).toList(),
              // After selecting the desired option,it will
              // change button value to selected value
              onChanged: (String? newValue) {
                setState(() {
                  dropdownvalue = newValue!;
                });
              },
            ),
          ],
        ),
      ),
    );
  }
}