How to use Functions of another File in Dart / Flutter?

Question

You can write a file with just that function, like:

test.dart

void launchWebView () {
  print("1234");
}

and then import that file like this:

main.dart

import "test.dart";

class _MyHomePageState extends State<MyHomePage> {
   @override
   Widget build(BuildContext context) {
       launchWebView();

It is not really clean, but you can do that.
Alternatively you can use a class with a static method like:

class test {
    static void foo() {
        print("1234");
    }
}

and then in your code invoke it like that (after the import):

test.foo();