flutter_tabbar.dart

class TabBarWidget extends StatefulWidget {
  @override
  _TabBarWidgetState createState() => _TabBarWidgetState();
}

class _TabBarWidgetState extends State<TabBarWidget> {

  List<Widget> _widgets = [
    DashboardPage(),
    SettingsWidget()
  ];

  static final titles = ['Dashboard', 'Settings'];

  PersistentTabController _controller;

  @override
  void initState() {
    super.initState();
    _controller = PersistentTabController(initialIndex: 0);
  }

  @override
  Widget build(BuildContext context) {
    var selectedColor = context.color(
        forLightMode: ThemeColors.lightTabBarContentActiveColor,
        forDarkMode: ThemeColors.darkTabBarContentActiveColor
    );
    var unselectedColor = context.color(
        forLightMode: ThemeColors.lightTabBarContentInactiveColor,
        forDarkMode: ThemeColors.darkTabBarContentInactiveColor
    );
    var backgroundColor = context.color(
        forLightMode: ThemeColors.lightTabBarBackgroundColor,
        forDarkMode: ThemeColors.darkTabBarBackgroundColor
    );
    var borderColor = context.color(
        forLightMode: ThemeColors.lightTabBarBorderColor,
        forDarkMode: Color(0xFF3333330)//ThemeColors.darkTabBarBorderColor
    );
    var border = Border(
        top: BorderSide(
            color: borderColor,
      )
    );

    Widget widget;
    if (context.isAndroid()) {
      widget = PersistentTabView(
        context,
        controller: _controller,
        screens: _widgets,
        items: [
          PersistentBottomNavBarItem(
              icon: Icon(Icons.dashboard),
              title: titles[0],
              activeColorPrimary: selectedColor,
              inactiveColorPrimary: unselectedColor,
              routeAndNavigatorSettings: RouteAndNavigatorSettings(onGenerateRoute: getRoutes)
          ),
          PersistentBottomNavBarItem(
              icon: Icon(Icons.settings),
              title: titles[1],
              activeColorPrimary: selectedColor,
              inactiveColorPrimary: unselectedColor,
              routeAndNavigatorSettings: RouteAndNavigatorSettings(onGenerateRoute: getRoutes)
          )
        ],
        confineInSafeArea: true,
        backgroundColor: Theme.of(context).backgroundColor,
        handleAndroidBackButtonPress: true, // Default is true.
        resizeToAvoidBottomInset: true, // This needs to be true if you want to move up the screen when keyboard appears. Default is true.
        stateManagement: true, // Default is true.
        hideNavigationBarWhenKeyboardShows: true, // Recommended to set 'resizeToAvoidBottomInset' as true while using this argument. Default is true.
        decoration: NavBarDecoration(
            colorBehindNavBar: Colors.white,
            border: border
        ),
        popAllScreensOnTapOfSelectedTab: true,
        popActionScreens: PopActionScreensType.all,
        itemAnimationProperties: ItemAnimationProperties( // Navigation Bar's items animation properties.
          duration: Duration(milliseconds: 200),
          curve: Curves.ease,
        ),
        navBarStyle: NavBarStyle.style8, // Choose the nav bar style with this property.
      );
    } else {
      widget = CupertinoTabScaffold(
          tabBar: CupertinoTabBar(
            activeColor: selectedColor,
            inactiveColor: unselectedColor,
            backgroundColor: backgroundColor,
            items: [
              BottomNavigationBarItem(
                label: titles[0],
                icon: Icon(Icons.dashboard),
              ),
              BottomNavigationBarItem(
                label: titles[1],
                icon: Icon(context.platformIcons.settings),
              ),
            ]
          ),
          tabBuilder: (context, index) => _getWidget(index)
      );
    }

    return WillPopScope (
      onWillPop: () async => false,
      child: widget,
    );
  }

  Widget _getWidget(int index) {
    return _widgets[index];
  }
}