Argument type 'Function' can't be assigned to the parameter type 'void' - flutter

Question

I am passing a call back function from my child file to the parent file, in the elevated button class, I am passing the function in the class (in the child file )to the named parameter on pressed, but I am getting the error in the question above, while it worked for the tutorial I am using(academind).
How do I solve this?
CHILD file
class Answer extends StatelessWidget {
final Function selectHandler;
Answer(this.selectHandler);
#override
Widget build(BuildContext context) {
return Container(
width: double.infinity,
child: ElevatedButton(
child: Text('Answer 1'),
style: ElevatedButton.styleFrom(
primary: Colors.lightGreen
),
onPressed: selectHandler,
),
);
}
}
PARENT file
// ignore_for_file: prefer_const_constructors, avoid_print, prefer_const_literals_to_create_immutables, must_be_immutable, prefer_const_constructors_in_immutables
import 'package:flutter/material.dart';
import './question.dart';
import './answer.dart';
void main() => runApp(MyApp());
class MyApp extends StatefulWidget {
MyApp({Key? key}) : super(key: key);
#override
State<StatefulWidget> createState() {
// ignore: todo
// TODO: implement createState
return _MyAppState();
}
}
class _MyAppState extends State <MyApp>{
var _questionsIndex = 0;
var questions = [
'What\'s your favourite book',
'What\'s your favourite colour',
'What\'s our favourite poem',
];
void _answerQuestion() {
setState(() {
_questionsIndex = _questionsIndex + 1;
if (_questionsIndex >= questions.length) _questionsIndex = 0;
});
print(_questionsIndex);
print(questions.length);
}
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(title: Text('My First App'),),
body: Column(
children: [
Question(
questions[_questionsIndex],
),
Answer(_answerQuestion),
Answer(_answerQuestion),
Answer(_answerQuestion),
],
)
),
);
}
}

Answer 1

Change Function to
void Function functionName(){}
or
VoidCallback functionName(){}

Answer 2

Same issue i have faced after updating this it is working
import 'package:flutter/material.dart';
class Answer extends StatelessWidget {
final VoidCallback clickFunction;
const Answer(this.clickFunction,{Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Container(
width: double.infinity,
padding: const EdgeInsets.all(5),
child: RaisedButton(
padding: const EdgeInsets.all(10),
color: Colors.blue,
onPressed: clickFunction,
child: const Text("This is texxt"),
));
}
}

Answer 3

this is worked for me
final void Function()? FunctionName;