flutter-examples/sliver_app_bar_example/lib/main.dart

import 'package:flutter/material.dart';

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

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

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: Scaffold(
          body: NestedScrollView(
            floatHeaderSlivers: true,
            headerSliverBuilder: (context, innerBoxIsScrolled) => [
              const SliverAppBar(
                expandedHeight: 240,
                flexibleSpace: FlexibleSpaceBar(
                  title: Text('Sliver App Bar Demo'),
                  background: Image(
                    image: AssetImage('assets/sample.jpg'),
                    fit: BoxFit.cover,
                  ),
                ),
                floating: true,
              ),
            ],
            body: ListView.separated(
                padding: const EdgeInsets.all(12),
                itemCount: 30,
                itemBuilder: (context, index) => ListTile(
                      title: Text('Item $index'),
                    ),
                separatorBuilder: (context, index) => const SizedBox(
                      height: 10,
                    )),
          ),
        ));
  }
}