Hide Bottom Navigation Bar On Scroll Down In Flutter Android

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

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  MyHomePageState createState() {
    return new MyHomePageState();
  }
}

class MyHomePageState extends State<MyHomePage> {
  String text = 'Home';
  ScrollController _scrollController;
  bool _visible = true;

  @override
  void initState() {
    super.initState();
    _scrollController = ScrollController();
    _scrollController.addListener(() {
      if (_scrollController.position.userScrollDirection == ScrollDirection.reverse) {
        setState(() => _visible = false);
      }

      if (_scrollController.position.userScrollDirection == ScrollDirection.forward) {
        setState(() => _visible = true);
      }
    });
  }

  _onTap(int index) {
    switch (index) {
      case 0:
        setState(() => text = 'Home');
        break;
      case 1:
        setState(() => text = 'Message');
        break;
      case 2:
        setState(() => text = 'Search');
        break;
      case 3:
        setState(() => text = 'Settings');
        break;
      default:
        setState(() => text = 'Home');
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: NestedScrollView(
        headerSliverBuilder: (context, boxScrolled) => [
          SliverAppBar(
            centerTitle: true,
            backgroundColor: Colors.indigo,
            title: Text("Hide BottomNavigation Bar"),
            pinned: true,
            floating: true,
            snap: false,
          ),
        ],
        body: ListView(
          controller: _scrollController,
          children: <Widget>[
            Padding(
              padding: const EdgeInsets.all(2.0),
              child: Image.asset("assets/images/slider5.jpg"),
            ),
            Padding(
              padding: const EdgeInsets.all(8.0),
              child: Image.asset("assets/images/slider2.jpg"),
            ),
            Padding(
              padding: const EdgeInsets.all(8.0),
              child: Image.asset("assets/images/slider3.jpg"),
            ),
            Padding(
              padding: const EdgeInsets.all(8.0),
              child: Image.asset("assets/images/slider4.jpg"),
            ),
          ],
        ),
      ),
      bottomNavigationBar: !_visible
          ? SizedBox()
          : BottomNavigationBar(
        type: BottomNavigationBarType.fixed,
        items: <BottomNavigationBarItem>[
          BottomNavigationBarItem(
            icon: Icon(Icons.home, color: Colors.indigo,),
            title: Text("Home",style: TextStyle(color: Colors.indigo),),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.message),
            title: Text("Message"),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.search),
            title: Text("Search"),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.settings),
            title: Text("Settings"),
          ),
        ],
        onTap: _onTap,
      ),
    );
  }
}