import 'package:flutter/material.dart';

void main() {
  runApp(const MaterialApp(home: MyApp()));
}

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

  @override
  Widget build(BuildContext context) => Scaffold(
    body: Padding(
      padding: const EdgeInsets.symmetric(horizontal: 64.0),
      child: CustomScrollView(
        reverse: true,
        physics: const BouncingScrollPhysics(),
        slivers: <Widget>[
          const _DecoratedSliver(
            isEnabled: true,
            // Here a simple SliverAppBar is used to demonstrate a pinned header sliver.
            sliver: SliverAppBar(
              pinned: true,
              stretch: true,
              expandedHeight: 100.0,
              surfaceTintColor: Colors.transparent,
              backgroundColor: Colors.transparent,
              flexibleSpace: FlexibleSpaceBar(title: Text('My header')),
            ),
          ),
          const _DecoratedSliver(
            sliver: PinnedHeaderSliver(child: ListTile(title: Text('A pinned header sliver'))),
          ),
          _DecoratedSliver(
            sliver: SliverMainAxisGroup(
              slivers: [
                PinnedHeaderSliver(
                  child: SizedBox(height: 150, child: const Center(child: Text('A SliverToBoxAdapter'))),
                ),
                SliverList.builder(
                  itemBuilder: (BuildContext context, int index) => ListTile(title: Text('Item $index')),
                  itemCount: 50,
                ),
              ],
            ),
          ),
        ],
      ),
    ),
  );
}

class _DecoratedSliver extends StatelessWidget {
  const _DecoratedSliver({this.isEnabled = true, required this.sliver});

  final bool isEnabled;
  final Widget sliver;

  @override
  Widget build(BuildContext context) => isEnabled
      ? DecoratedSliver(
          decoration: BoxDecoration(
            border: Border.all(),
            borderRadius: BorderRadius.circular(8),
            gradient: const LinearGradient(
              begin: Alignment.topCenter,
              end: Alignment.bottomCenter,
              colors: [Colors.blue, Colors.purple],
            ),
          ),
          sliver: sliver,
        )
      : sliver;
}