cupertinosegmentedcontrol

main.dart

import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';

void main() {
  runApp(
    MaterialApp(
      home: HomeScreen(),
    ),
  );
}

class HomeScreen extends StatefulWidget {
  @override
  _HomeScreenState createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen>
    with SingleTickerProviderStateMixin {
  TabController _tabController;

  final Map<int, Widget> pages = const <int, Widget>{
    0: Text("Symptoms"),
    1: Text("Prevention"),
  };
  int currentIndex = 0;

  @override
  void initState() {
    _tabController = new TabController(length: 2, vsync: this);
    _tabController.addListener(() {
      setState(() {
        currentIndex = _tabController.index;
      });
    });
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Column(
        children: <Widget>[
          PreferredSize(
            preferredSize: const Size.fromHeight(48.0),
            child: CupertinoSegmentedControl(
              children: pages,
              groupValue: currentIndex,
              onValueChanged: (int val) {
                setState(
                  () {
                    this._tabController.index = val;
                  },
                );
              },
            ),
          ),
          Expanded(
            child: TabBarView(
              controller: _tabController,
              children: <Widget>[
                ListView.builder(
                  itemCount: 20,
                  itemBuilder: (context, i) {
                    return Text("$i");
                  },
                ),
                Text("Page 2"),
              ],
            ),
          ),
        ],
      ),
    );
  }
}