Remember the state of bottomNavigation bar when back to a page flutter

Question

In main_activity.dart, there has 4 bottom navigation bar, named A,B,C and D.

main_activity.dart

class MainPage extends StatefulWidget {
  static const ROUTE = '/mainPage';

  @override
  State<StatefulWidget> createState() => _MainPageState();
}

class _MainPageState extends State<MainPage> {
  int _selectedIndex = 2;
  final _tabs = [
    A(),
    B(),
    C(),
    D(),
  ];

  @override
  Widget build(BuildContext context) {
    return WillPopScope(
      child: Scaffold(
        body: _tabs[_selectedIndex],
        bottomNavigationBar: BottomNavigationBar(
          type: BottomNavigationBarType.fixed,
          currentIndex: _selectedIndex,
          items: [
           ...
          ],
          onTap: (index) => setState(() {
            _selectedIndex = index;
          }),
        ),
      ),
       onWillPop: () => _requestPop(context),
    );
  }
}

Initially it will open page in tab C. When I click tab B, it will show B page which contains a floating action button. When floating action button is clicked, it will call add_B.dart. My problem is when I click the back button in add_B.dart, it will back to main_activity and open tab C page. How can I make it open tab B page instead?

add_B.dart

onWillPop: (){
        _backToPreviousPage(context);
      },

 void _backToPreviousPage(BuildContext context) {
    Navigator.of(context).pushReplacementNamed(MainPage.ROUTE);
  }

Solution

You can create global.dart file and in it declare int _selectedIndex = 2; and import the file whenever you use it if you set _selectedIndex to a certain value the value is saved with you all over the app.

Comments

[John Joe]

let say I click the back button in add_B.dart. How can I load tab B state?

[Mohamed Adel]

before you navigate to the next page set _selectedIndex to the desired index

[John Joe]

yes, I have done that. onTap: (index) => setState(() { _selectedIndex = index; }),

[John Joe]

But when I back from add_B, it load the third tab page @@

[John Joe]

Is it because Navigator.of(context).pushReplacementNamed(MainPage.ROUTE); ?

[Mohamed Adel]

try to pass _selectedIndex = 1; statically

[John Joe]

how can I pass ? Thanks

[Mohamed Adel]

onWillPop: () { //here _requestPop(context);}

[John Joe]

Let us continue this discussion in chat.