如何在某些屏幕上显示/隐藏底部导航栏？

Question

此blog显示了如何使用PageStorage保留页面状态

此blog在每个屏幕上显示多个导航。底部导航栏在所有屏幕上均保持不变

但是如何使BottomNavigationBar在某些屏幕上显示/隐藏？说，登录/注册/成功的屏幕？试图为BottomNavigationBar创建一个有状态的窗口小部件，但是每次使用导航栏时，都会重置导航栏的selectedIndex。我似乎无法使其正常工作。

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Text('app_screen'),
      bottomNavigationBar: AppBottomNavigationController(),
    );
  }
}

app_bottom_navigation_controller.dart

class AppBottomNavigationController extends StatefulWidget {
  @override
  _AppBottomNavigationControllerState createState() =>
      _AppBottomNavigationControllerState();
}

class _AppBottomNavigationControllerState
    extends State<AppBottomNavigationController> {
  int currentIndex = 0;
  final List<Widget> pages = [];
  final PageStorageBucket bucket = PageStorageBucket();

  @override
  void initState() {
    pages.addAll([
      HomeScreen(
        key: PageStorageKey('home_screen'),
      ),
      SearchScreen(
        key: PageStorageKey('search_screen'),
      ),
      AccountScreen(
        key: PageStorageKey('account_screen'),
      )
    ]);
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: PageStorage(
        child: pages[currentIndex],
        bucket: bucket,
      ),
      bottomNavigationBar: _bottomNavigationBar(currentIndex),
    );
  }

  Widget _bottomNavigationBar(int selectedIndex) {
    return BottomNavigationBar(
      currentIndex: selectedIndex,
      onTap: (index) => setState(() => currentIndex = index),
      items: [
        BottomNavigationBarItem(
          icon: Icon(Icons.home),
          title: Text('Home'),
        ),
        BottomNavigationBarItem(
          icon: Icon(Icons.search),
          title: Text('Search'),
        ),
        BottomNavigationBarItem(
          icon: Icon(Icons.person),
          title: Text('Account'),
        ),
      ],
    );
  }
}

然后在account.dart屏幕下，我有account_bag.dart和account_successful.dart屏幕。我想在account_bag.dart屏幕上显示底部导航栏，而在account_successful.dart屏幕上显示导航栏。