import 'package:flutter/material.dart';
final GlobalKey<NavigatorState> navigator = GlobalKey<NavigatorState>();
void main() {
  runApp(MaterialApp(home:TapBox()));
}

class TapBox extends StatelessWidget {
  TapBox({Key key}) : super(key: key);
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        actions: [
          // action button
          IconButton(icon: const BackButtonIcon(), onPressed: () {}),
        ],
      ),
      body: TapboxA(),
    );
  }
}
 
class TapboxA extends StatefulWidget {
  TapboxA({Key key}) : super(key: key);
 
  @override
  _TapboxAState createState() => _TapboxAState();
}
 
class _TapboxAState extends State<TapboxA> {
  bool _active = false;
 
  final pageViewKey = GlobalKey();
  final pageController = PageController(initialPage: 0, viewportFraction: 0.15);
 
  void _handleTap() {
    setState(() {
      _active = !_active;
    });
  }
 
  @override
  Widget build(BuildContext context) {
    return _active
        ? _buildPageView(
      context,
    )
        : Semantics(
            key: ValueKey<int>(1),
            scopesRoute: true,
            explicitChildNodes: true,
            child: Semantics(
              namesRoute: true,
              label: 'PageView widget',
              onTap: _handleTap,
              excludeSemantics: true,
              child: _buildPageView(
                context,
              ),
            )
          );
  }
 
  Widget _buildPageView(BuildContext context) {
    return Semantics(
      key: ValueKey<int>(0),
      scopesRoute: true,
      explicitChildNodes: true,
      child: PageView.builder(
        key: pageViewKey,
        controller: pageController,
        allowImplicitScrolling: true,
        itemCount: 20,
        itemBuilder: (_, index) => _buildItem(
          context,
          index: index,
        ),
      )
    );
  }
 
  Widget _buildItem(
      BuildContext context, {
        int index,
      }) {
    return Semantics(
      label: 'label',
      namesRoute: true,
      button: true,
      excludeSemantics: true,
      onTap: () async {
        await _animateToPage(index);
        _handleTap();
      },
      child: Center(child: const Text('text')),
    );
  }
 
  Future<void> _animateToPage(int page) {
    return pageController.animateToPage(
      page,
      duration: const Duration(milliseconds: 400),
      curve: Curves.easeInOut,
    );
  }
}