Callback from child to parent Flutter - flutter

Question

I am new to flutter. I am trying to separate the bottomappbar widget from my home screen. Thing is, it is I need to send back the index to the home screen file so I can switch the body of the screen. I've been learning BloC lately, but I think it is an overkill for this case, even though I am going to use it in other parts of the app (hopefully this is the right assumption). So, how can I send the index to the parent?
Parent
class HomeScreen extends StatefulWidget {
#override
_HomeScreenState createState() => _HomeScreenState();
}
class _HomeScreenState extends State<HomeScreen> {
int _selectedIndex = 0;
final _bottomNavigationPages = [
Screen1(),
Screen2(),
];
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
iconTheme: IconThemeData(
color: Colors.blueGrey,
),
title:
Text('xxx', style: new TextStyle(fontWeight: FontWeight.w400)),
),
body: _bottomNavigationPages[_selectedIndex],
bottomNavigationBar: HomeBottomAppBar(),
);
}
}
Child
class HomeBottomAppBar extends StatefulWidget {
#override
_HomeBottomAppBarState createState() => _HomeBottomAppBarState();
}
class _HomeBottomAppBarState extends State<HomeBottomAppBar> {
int _selectedIndex = 0;
void _itemTapped(int index) {
setState(() {
_selectedIndex = index;
});
}
#override
Widget build(BuildContext context) {
return BottomAppBar(
shape: CircularNotchedRectangle(),
notchMargin: 5.0,
clipBehavior: Clip.antiAlias,
child: BottomNavigationBar(
items: [
BottomNavigationBarItem(
icon: Icon(Icons.x), title: Text("1")),
BottomNavigationBarItem(
icon: Icon(Icons.x), title: Text("2")),
],
currentIndex: _selectedIndex,
onTap: _itemTapped,
),
);
}
}
Also, I am going under the assumption that this is good practice. Maybe it is just better to have everything in the same file.

Answer 1

class HomeScreen extends StatefulWidget {
#override
_HomeScreenState createState() => _HomeScreenState();
}
class _HomeScreenState extends State<HomeScreen> {
int _selectedIndex = 0;
final _bottomNavigationPages = [
Screen1(),
Screen2(),
];
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
iconTheme: IconThemeData(color: Colors.blueGrey),
title: Text('xxx', style: new TextStyle(fontWeight: FontWeight.w400)),
),
body: _bottomNavigationPages[_selectedIndex],
bottomNavigationBar: HomeBottomAppBar(refresh: _refresh),
);
}
void _refresh(int index) {
setState(() {
_selectedIndex = index;
});
}
}
class HomeBottomAppBar extends StatefulWidget {
final Function refresh;
const HomeBottomAppBar({Key key, this.refresh}) : super(key: key);
#override
_HomeBottomAppBarState createState() => _HomeBottomAppBarState();
}
class _HomeBottomAppBarState extends State<HomeBottomAppBar> {
int _selectedIndex = 0;
void _itemTapped(int index) {
_selectedIndex = index;
widget.refresh(index);
}
#override
Widget build(BuildContext context) {
return BottomAppBar(
shape: CircularNotchedRectangle(),
notchMargin: 5.0,
clipBehavior: Clip.antiAlias,
child: BottomNavigationBar(
items: [
BottomNavigationBarItem(icon: Icon(Icons.x), title: Text("1")),
BottomNavigationBarItem(icon: Icon(Icons.x), title: Text("2")),
],
currentIndex: _selectedIndex,
onTap: _itemTapped,
),
);
}
}