// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Flutter code sample for NestedScrollView

import 'package:flutter/material.dart';

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

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

  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: _title,
      home: MyStatelessWidget(),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: NestedScrollView(headerSliverBuilder:
            (BuildContext context, bool innerBoxIsScrolled) {
      return <Widget>[
        SliverOverlapAbsorber(
          handle: NestedScrollView.sliverOverlapAbsorberHandleFor(context),
          sliver: SliverAppBar(
            title: const Text('Snapping Nested SliverAppBar'),
            floating: true,
            snap: true,
            expandedHeight: 200.0,
            forceElevated: innerBoxIsScrolled,
          ),
        )
      ];
    }, body: Builder(builder: (BuildContext context) {
      return CustomScrollView(
        // The "controller" and "primary" members should be left
        // unset, so that the NestedScrollView can control this
        // inner scroll view.
        // If the "controller" property is set, then this scroll
        // view will not be associated with the NestedScrollView.
        slivers: <Widget>[
          SliverOverlapInjector(
              handle: NestedScrollView.sliverOverlapAbsorberHandleFor(context)),
          SliverFixedExtentList(
            itemExtent: 48.0,
            delegate: SliverChildBuilderDelegate(
              (BuildContext context, int index) =>
                  ListTile(title: Text('Item $index')),
              childCount: 30,
            ),
          ),
        ],
      );
    })));
  }
}