How to get query parameters from URL in Angular 5?

I’m using angular 5.0.3, I would like to start my application with a bunch of query parameters like /app?param1=hallo&param2=123. Every tip given in How to get query params from url in Angular 2? does not work for me.

Any ideas how to get query parameters work?

private getQueryParameter(key: string): string {
  const parameters = new URLSearchParams(window.location.search);
  return parameters.get(key);
}

This private function helps me to get my parameters, but I don’t think it is the right way in new Angular environment.

[update:]
My main app looks like

@Component({...})
export class AppComponent implements OnInit {

  constructor(private route: ActivatedRoute) {}

  ngOnInit(): void {
    // would like to get query parameters here...
    // this.route...
  }
}