Parent components gets empty Params from ActivatedRoute

If you'd like to access the router parameters via a service, this approach will not work! consider using a service to prevent the replication of the "Route params value extraction logic" (from this Medium article):

@Injectable({
  providedIn: 'root'
})
export class MyParamsAwareService {
  constructor(private router: Router) { 
    this.router.events
      .pipe(
        filter(e => (e instanceof ActivationEnd) && (Object.keys(e.snapshot.params).length > 0)),
        map(e => e instanceof ActivationEnd ? e.snapshot.params : {})
      )
      .subscribe(params => {
      console.log(params);
      // Do whatever you want here!!!!
      });
  }
}

ActivatedRoute: Contains the information about a route associated with a component loaded in an router outlet. If you would like to access route details outside of it, use the code below.

import { Component } from '@angular/core';
import { Router, ActivatedRoute, Params, RoutesRecognized } from '@angular/router';

export class AppComponent {

    constructor(private route: ActivatedRoute, private router: Router) {

    }

    ngOnInit(): void {
        this.router.events.subscribe(val => {

            if (val instanceof RoutesRecognized) {

                console.log(val.state.root.firstChild.params);

            }
        });

    }
}

There are other ways to share data in between components for example by using a service.

For more details about how you can tackle this as concept, read comments here.

The Very simple answer

import { Component } from '@angular/core';
import { Router, ActivatedRoute, Params, RoutesRecognized } from '@angular/router';

export class AppComponent {

    constructor(private actRoute: ActivatedRoute, private router: Router){}

    ngOnInit(): void {
        this.actRoute.firstChild.params.subscribe(
            (params: any) => {
                if (params.hasOwnProperty('<whatever the param name>') != '') {
                    //do whatever you want
                    console.log(params.<whatever the param name>);
                } 
            });
    }
}

ActivatedRoute works for components loaded via router-outlet. From docs - it:

Contains the information about a route associated with a component loaded in an outlet.

I don't think you can use it in components that are not loaded in an outlet. It also doesn't work in base classes your component extends.

class A { constructor(public route: ActivatedRoute) } 
class B extends A { ngOnInit() { this.route; } }        // not working
class C { constructor(public route: ActivatedRoute) }   // working if loaded in outlet