platform_parent.dart

class PlatformParent extends PlatformWidget<CupertinoTabScaffold, Scaffold> {
  ...

  PlatformParent({...});

  @override
  Scaffold createAndroidWidget(BuildContext context) {
    return Scaffold(
        ...,
        appBar: buildTabBar(this.showTabs, context),
        body: TabBarView(
          children: this.children,
        ),
        bottomNavigationBar: BottomNavigationBar(
          ...,
          items: _buildNavigationItems(),
        ));
  }

  Widget buildTabBar(bool showTabs, BuildContext context) {
    return AppBar(
      bottom: showTabs
          ? TabBar(
              indicatorColor: VoiceTheme.blaze_orange,
              tabs: _buildTabs(),
            )
          : null,
    );
  }

  @override
  CupertinoTabScaffold createIosWidget(BuildContext context) {
    final Map<int, Widget> children = <int, Widget>{
      0: Text(countries[0].label),
      1: Text(countries[1].label),
      2: Text(countries[2].label),
    };

    return CupertinoTabScaffold(
      tabBar: CupertinoTabBar(
        ...,
        items: _buildNavigationItems(),
      ),
      tabBuilder: (BuildContext context, int index) {
        return CupertinoPageScaffold(
          navigationBar: CupertinoNavigationBar(
            middle: showTabs
                ? SizedBox(
                    width: 500.0,
                    child: CupertinoSegmentedControl(
                      ...
                      children: children,
                    ))
                : Container(),
          ),
          child: Scaffold(
            body: this.children[0],
          ),
        );
      },
    );
  }

  List<Widget> _buildTabs() {
    return <Widget>[
      PlatformTabs(label: countries[0].label),
      PlatformTabs(label: countries[1].label),
      PlatformTabs(label: countries[2].label),
    ];
  }

  List<BottomNavigationBarItem> _buildNavigationItems() {
    return <BottomNavigationBarItem>[
      BottomNavigationBarItem(
        icon: Icon(
          FontAwesomeIcons.handHoldingHeart,
          size: 26,
        ),
        title: Text(categories[0].label),
      ),
      ...,
    ];
  }
}