How to modify parent FloatingActionButton on flutter? - flutter

Question

I am making an app in which I have to pages, routed by a BottomNavigationBar, and each page has its own nested routes. The app contains a main FloatingActionButton centered and docked into the BottomNavigationBar. The problem is that I wanted to control what the FAB does from inside each nested route. The problem is that if I create a FAB inside each nested route the button will not be docked into the BottomNavigationBar. Bellow are some pictures. Anyone can help? Thanks in advance.
What I have :
What I wanted :

Answer 1

Is this what you are asking? If not please share some code which casing the problem
UPDATE
Scaffold(
appBar: AppBar(
title: Text('Test'),
),
body: _screenList[_screenIndex],
bottomNavigationBar: BottomNavigationBar(
type: BottomNavigationBarType.fixed,
currentIndex: _screenIndex,
onTap: (index) {
print(index);
setState(() {
_screenIndex = index;
});
},
items: [
BottomNavigationBarItem(
icon: Icon(Icons.inbox),
title: Text('Screen1'),
),
BottomNavigationBarItem(
icon: Icon(Icons.search),
title: Text('Screen2'),
),
]),
floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
floatingActionButton: FloatingActionButton(
child: Icon(
Icons.android,
),
onPressed: () {
_screenIndex == 0
? print('hello from screen1')
: print('hello from screen2');
},
),
);
OUTPUT