import 'package:flutter/material.dart';

​

void main() => runApp(MyApp());

​

class MyApp extends StatelessWidget {

  @override

  Widget build(BuildContext context) {

    return MaterialApp(

      home: Scaffold(

        body: Center(

          child: MyCustomButton(

            onValueChanged: (value) {

              print("ValueChanged: $value");

            },

            onCallback: () {

              print("Callback function executed");

            },

            someFunction: (int number) {

              print("Function with parameter: $number");

            },

          ),

        ),

      ),

    );

  }

}

​

class MyCustomButton extends StatelessWidget {

  final ValueChanged<int> onValueChanged; // Takes a value as a parameter

  final Function someFunction;            // Takes a parameter but doesn't return a value

  final VoidCallback onCallback;          // Doesn't take a parameter or return a value

​

  MyCustomButton({

    required this.onValueChanged,

    required this.someFunction,

    required this.onCallback,

  });

​

  @override

  Widget build(BuildContext context) {

    return ElevatedButton(

      onPressed: () {

        onValueChanged(42);      // Calling ValueChanged

        someFunction(10);        // Calling Function

        onCallback();            // Calling VoidCallback

      },

      child: Text("Press me"),

    );

  }

}