Unable to call a method in another dart file - flutter

Question

I have a dart file with IndexedStack and the following function in the same file to change the stacks.
The file with method as follows-
class RootApp extends StatefulWidget with selectedTab {
#override
_RootAppState createState() => _RootAppState();
}
class _RootAppState extends State<RootApp> {
int pageIndex = 0;
List<Widget> pages = [
......
];
#override
void initState() {
super.initState();
}
#override
void dispose() {
super.dispose();
}
#override
Widget build(BuildContext context) {
....
return AnimatedBottomNavigationBar(
.......
onTap: (index) {
selectedTab(index);
},
);
}
selectedTab(index) {
setState(() {
pageIndex = index;
});
}
}
There is this other dart file from which i would like to call selectedTab method with value of 0. The other file is as follows---
class CreatBudgetPage extends StatefulWidget {
#override
_CreatBudgetPageState createState() => _CreatBudgetPageState();
}
class _CreatBudgetPageState extends State<CreatBudgetPage> {
.......
FirebaseFirestore.instance
.collection('expenses/' + userId + '/' + todayDate)
.add({
....
}).then((_) {
print("collection created");
void rootApp() => selectedTab(0);
}).catchError((error) {
print(error);
});
}
How can i call this method from the other dart file?
P.S: I am a Newbie

Answer 1

You can pass the function callback as parameters from the source class to the intended class and invoke the function as you want.
here is a simple example.
class Example extends StatefulWidget {
const Example({Key? key}) : super(key: key);
#override
_ExampleState createState() => _ExampleState();
}
class _ExampleState extends State<Example> {
int pageIndex = 0;
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('BottomNavigationBar Sample'),
),
body: IndexedStack(
index: pageIndex,
children: [
Tab1Page(),
Tab2Page(
/// solution 1
onPressed1: () {
selectedTab(0);
},
/// solution 2
// onPressed2: selectedTab,
),
],
),
bottomNavigationBar: BottomNavigationBar(
items: const <BottomNavigationBarItem>[
BottomNavigationBarItem(
icon: Icon(Icons.home),
label: 'TAB 1',
),
BottomNavigationBarItem(
icon: Icon(Icons.business),
label: 'TAB 2',
),
],
currentIndex: pageIndex,
selectedItemColor: Colors.amber[800],
onTap: selectedTab,
),
);
}
selectedTab(index) {
setState(() {
pageIndex = index;
});
}
}
class Tab1Page extends StatelessWidget {
const Tab1Page({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Container(
color: Colors.red,
child: Center(
child: Text(
"Tab1",
style: TextStyle(fontSize: 20),
),
),
);
}
}
class Tab2Page extends StatelessWidget {
final VoidCallback? onPressed1;
// final Function(int)? onPressed2;
const Tab2Page({
Key? key
/// solution 1
,
this.onPressed1,
/// solution 2
// this.onPressed2
}) : super(key: key);
#override
Widget build(BuildContext context) {
return Container(
color: Colors.red,
child: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Text(
"Tab2",
style: TextStyle(fontSize: 20),
),
ElevatedButton(
onPressed: () {
/// solution 1
if (onPressed1 != null) {
onPressed1!();
}
/// solution 2
// if(onPressed2!=null){
// onPressed2!(0);
//
// }
},
child: Text("click to navigate to another tab",
style: TextStyle(fontSize: 20)),
),
],
),
),
);
}
}