import 'dart:io';

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primaryColor: Colors.white,
      ),
      home: NewsScreen(),
      debugShowCheckedModeBanner: false,
    );
  }
}

class NewsScreen extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _NewsScreenState();
}

class _NewsScreenState extends State<NewsScreen> {
  final List<String> _tabs = <String>[
    "Featured",
    "Popular",
    "Latest",
  ];

  @override
  Widget build(BuildContext context) {
    return Material(
      child: Scaffold(
        body: DefaultTabController(
          length: _tabs.length,
          child: NestedScrollView(
            headerSliverBuilder:
                (BuildContext context, bool innerBoxIsScrolled) {
              return <Widget>[
                SliverOverlapAbsorber(
                  handle:
                      NestedScrollView.sliverOverlapAbsorberHandleFor(context),
                  child: SliverSafeArea(
                    top: false,
                    bottom: Platform.isIOS ? false : true,
                    sliver: SliverAppBar(
                      title: Text('Tab Demo'),
                      floating: true,
                      pinned: true,
                      snap: true,
                      forceElevated: innerBoxIsScrolled,
                      bottom: TabBar(
                        tabs: _tabs
                            .map((String name) => Tab(text: name))
                            .toList(),
                      ),
                    ),
                  ),
                ),
              ];
            },
            body: TabBarView(
              children: _tabs.map((String name) {
                return SafeArea(
                  top: false,
                  bottom: false,
                  child: Builder(
                    builder: (BuildContext context) {
                      return NotificationListener<ScrollNotification>(
                        onNotification: (scrollNotification) {
                          return true;
                        },
                        child: CustomScrollView(
                          key: PageStorageKey<String>(name),
                          slivers: <Widget>[
                            SliverOverlapInjector(
                              handle: NestedScrollView
                                  .sliverOverlapAbsorberHandleFor(context),
                            ),
                            SliverPadding(
                              padding: const EdgeInsets.all(8.0),
                              sliver: SliverList(
                                delegate: SliverChildBuilderDelegate(
                                  (BuildContext context, int index) {
                                    return Column(
                                      children: <Widget>[
                                        Container(
                                          height: 150,
                                          width: double.infinity,
                                          color: Colors.blueGrey,
                                          child: Column(
                                            mainAxisAlignment:
                                                MainAxisAlignment.center,
                                            children: <Widget>[
                                              Text('$name $index')
                                            ],
                                          ),
                                        ),
                                        SizedBox(
                                          height: 8,
                                        )
                                      ],
                                    );
                                  },
                                  childCount: 30,
                                ),
                              ),
                            ),
                          ],
                        ),
                      );
                    },
                  ),
                );
              }).toList(),
            ),
          ),
        ),
      ),
    );
  }
}