Flutter BottomNavigationBar nasıl gösterilir?

Böyle bir root page yazdım fakat istediğim sayfalarda bottomNavigationBar'ı nasıl gösterceğimi bilmiyorum, nasıl yapmalıyım? Yani tabPages de gösterilen sayfalarda nasıl bu yazdığım Navigation bar'ı göstereceğim?

Kod 
Yığını:
import 'dart:async';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:google_nav_bar/google_nav_bar.dart';
import 'package:mythgames/core/init/constants/widget_constants.dart';
import 'package:mythgames/presentation/pages/homepage/homepage_screen.dart';
import 'package:mythgames/presentation/pages/profile/profile_screen.dart';
import 'package:mythgames/presentation/pages/settings/settings_screen.dart';

class RootPage extends StatefulWidget {


  _RootPageState createState() => _RootPageState();
}

class _RootPageState extends State{

  int selectedTab = 0;
  late PageController _pageController;

  List tabPages = [
    HomepageScreen(),
    SettingsScreen(),
    ProfileScreen()
  ];

  @override
  void initState() {
    _pageController = PageController(initialPage: selectedTab);
    super.initState();
  }

  @override
  void dispose() {
    _pageController.dispose();
    super.dispose();
  }
  Color iconColor = Color(0xFFC4D9FF);

  final GlobalKey _scaffoldKey = GlobalKey();
  @override
  Widget build(BuildContext context) {

    double widthSize = resWidthSize(context);
    double heightSize = resHeightSize(context);

    return GestureDetector(
      onTap: () => FocusScope.of(context).requestFocus(new FocusNode()),
      child: Scaffold(
        backgroundColor: Colors.black,
          key: _scaffoldKey,
          bottomNavigationBar: ClipRRect(
            borderRadius: const BorderRadius.only(
              topRight: Radius.circular(40),
              topLeft: Radius.circular(40),
            ),
            child: Container(
              color: const Color(0xFF2a2319),
              child:  Padding(
                padding: const EdgeInsets.symmetric(horizontal: 15,vertical: 20),
                child: GNav(
                  selectedIndex: selectedTab,
                  tabBorderRadius: WidgetConstants.borderRadius1,
                  gap: 8,
                  backgroundColor: const Color(0xFF2a2319),
                  color: const Color(0xFF625546),
                  activeColor: const Color(0xFFffffff),
                  tabBackgroundColor:const Color(0xFFac8c6b),
                  padding: const EdgeInsets.all(9),
                  onTabChange: onTabTapped,
                  tabs: const [
                    GButton(
                      icon: Icons.home_filled,
                      text: "Home",
                      textStyle:  TextStyle(
                        fontSize: 15,
                        fontFamily: "Inter",
                        fontWeight: FontWeight.w500,
                        color: Color(0xFFffffff),
                      ),
                    ),
                    GButton(
                      icon: Icons.explore_outlined,
                      text: "Search",
                      textStyle: TextStyle(
                        fontSize: 15,
                        fontFamily: "Inter",
                        fontWeight: FontWeight.w500,
                        color: Color(0xFFffffff),
                      ),
                    ),
                    GButton(
                      icon: Icons.person_outline,
                      text: "Profile",
                      textStyle: TextStyle(
                        fontSize: 15,
                        fontFamily: "Inter",
                        fontWeight: FontWeight.w500,
                        color: Color(0xFFffffff),
                      ),
                    ),
                  ],
                ),
              ),
            ),
          ),
        body: PageView(
          children: tabPages,
          onPageChanged: onPageChanged,
          controller: _pageController,
          physics: NeverScrollableScrollPhysics(),
        ),
      ),
    );
  }

  void onPageChanged(int page) {
    // PageView onPageChanged
    setState(() {
      this.selectedTab = page;
    });
  }

  void onTabTapped(int index) {  // BottomNavigatonBar OnTap
    FocusScope.of(context).requestFocus(new FocusNode());
    this._pageController.jumpToPage(index);
  }




  double resWidthSize(BuildContext context){
    double widthSize;
    if(MediaQuery.of(context).size.width>598)  widthSize = MediaQuery.of(context).size.width * 0.0072;
    else widthSize = MediaQuery.of(context).size.width * 0.01;
    return widthSize;
  }
  double resHeightSize(BuildContext context){
    double heightSize = MediaQuery.of(context).size.height * 0.01;
    return heightSize;
  }
}

Bir tane StatefulWidget oluştur tab diye. En aşağısına bir bar koy. Tıklamana göre üstte widget göster.