Flutter rebuilds previous routes when focusing on TextField

Question

My project is structured with Blocs and Statefull widget. Which worked fine until now. Everytime I focus on a Textfield it rebuilds the entire chain, meaning all the routes behind it. I mean when routes are pushed one route can't access the context of the other routes right?

MaterialApp
   -> Home(context)

//pushed a route

MaterialApp
  -> NewPage(context) //it's doesn't interfere with Home
  -> Home(context)

So how does it happens to rebuilds everything? Only this particular rebuilding of widget is causing the issue other wise everything else is fine.

Overview of what happens:

1. CheckoutPage is pushed on the stack from the cart page

2. User Selects to add new location

3. Selects TextField

4. All the previous routes are rebuild

Codes: This is how my routes are defined

routes: {
...
'/checkout': (context) => BlocProvider(
      bloc: CheckoutBloc(),
      child: BlocProvider( //statefull widget
        bloc: LocationBloc(),
        child: CheckoutPage(),
      ),
    ),
'/locations/new': (context) => BlocProvider(
          bloc: NewLocationBloc(),
          child: NewLocationModal(),
        )
...
}

All the widgets are Statefull. The checkout page contains list of widgets.

class _CheckoutPageState extends State < CheckoutPage > {
  final Key _scaffold = GlobalKey < ScaffoldState > ();
  //Pages
  //1. Cart Summary
  //2. Address
  //3. Appoint Schdule
  //4. Payment
  //5  Confirmation
  int initialData = 0;
  List < Widget > _pages = [
    CartSummary(),
    LocationPage(),
    AppointmentSchedule(),
    Payment(),
    Confirmation()
  ];
  List < String > _pageTitle = [
    'Cart Summary',
    'Address',
    'Schedule Appointment',
    'Payment',
    'Confirmation'
  ];
  final PageController controller = PageController(initialPage: 0);
  @override
  Widget build(BuildContext context) {
    final CheckoutBloc bloc = BlocProvider.of < CheckoutBloc > (context);
    return BlocProvider(
      bloc: cartBloc,
      child: Scaffold(
        resizeToAvoidBottomInset: true,
        key: _scaffold,
        body: PageView(
          key: PageStorageKey('checkout'),
          onPageChanged: (int index) {
            bloc.changePage(index);
          },
          controller: controller,
          children: _pages,
        ),
      ),
      // ),
    );
  }
}

Now when I push to a new route both named/unamed and click on any TextField it rebuilds the previous routes which are on stack and the Blocs get re-instantiated.

class _NewLocationModalState extends State < NewLocationModal > {
  static final _scaffoldKey = GlobalKey < ScaffoldState > ();
  static final _form = GlobalKey < FormState > ();
  final TextEditingController _name = TextEditingController();
  @override
  Widget build(BuildContext context) {
    final NewLocationBloc bloc = BlocProvider.of < NewLocationBloc > (context);
    return Scaffold(
      key: _scaffoldKey,
      resizeToAvoidBottomInset: true,
      appBar: AppBar(
        automaticallyImplyLeading: false,
        leading: IconButton(
          icon: Icon(Icons.close),
          onPressed: () {
            Navigator.pop(context, null);
          },
        ),
        title: Text('New address'),
      ),
      body: SingleChildScrollView(
        child: Form(
          key: _form,
          child: Padding(
            padding: const EdgeInsets.symmetric(horizontal: 18),
              child: Column(
                mainAxisSize: MainAxisSize.min,
                children: < Widget > [
                  Container(
                    color: Colors.lightGreenAccent,
                    height: 300,
                    child: Center(
                      child: Text('TODO// ADD Gmaps'),
                    ),
                  ),
                  TextFormField(
                    // autofocus: true,
                    decoration: InputDecoration(hintText: 'Client Name'),
                    controller: _name,
                    validator: (val) {
                      if (val.length <= 0) return "Can't be left blank";
                      return null;
                    },
                  ),
                ],
              ),
          ),
        ),
      ),
    );
  }
}

Is this a expected behavior to rebuild the previous routes too?

How do I structure my project to solve this issue?

There is a closed GitHub issue but there isn't anything helpful in it. https://github.com/flutter/flutter/issues/37878