Pass function as arguments

main.dart

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyHomePage(testest: () {
        print('test');
      }),
    );
  }
}

class MyHomePage extends StatefulWidget {
  final VoidCallback testest;
  MyHomePage({@required this.testest});
  @override
  _MyHomePage createState() => _MyHomePage();
}

class _MyHomePage extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      drawer:
          Drawer(child: ListTile(title: Text("test"), onTap: widget.testest)),
      body: Column(children: [Text("Hello World")]),
    );
  }
}