Angular 4: access an Openlayers 'overlay' element

Question

How can I use an Openlayer 'overlay' inside Angular? I think the best way is via a @Viewchild construction. So, not via document.getElementById('overlay').

In the HTML file I have something like.

<div #overlayElement id="overlay" style="background-color: yellow; width: 20px; height: 20px; border-radius: 10px;">
<div #mapElement id="map" class="map"> </div>

The non-Angular solution is attaching the overlay logic to the Html 'overlay' element via the 'element: document.getElementById('overlay')'. That works.

UPDATE: thanks to @ zerO the logic is moved from the constructor to the ngOnInit().

In my Angular component I hoped to attach the overlay Html element with a viewtag "#overlayElement". In my component code I hoped to access it via a @Viewchild. I get a strange [Object object] error.

declare var ol: any;

@Component({
  selector: 'app-tab4-controls',
  templateUrl: './tab4-controls.component.html',
  styleUrls: ['./tab4-controls.component.css']
})
export class Tab4ControlsComponent implements AfterViewInit, OnInit {

@ViewChild('mapElement') mapElement: ElementRef;
@ViewChild('overlayElement') overlayElement: ElementRef;
public map: any;

constructor() { }

ngOnInit(): void {

  const layer = new ol.layer.Tile({
    source: new ol.source.OSM()
  });
  const interaction = new ol.interaction.DragRotateAndZoom();
  const control = new ol.control.FullScreen();
  const center = ol.proj.transform([-1.812, 52.443], 'EPSG:4326', 'EPSG:3857');
  const overlay = new ol.Overlay({
    position: center,
    // element: document.getElementById('overlay') <== this works
    element : this.overlayElement.nativeElement.id
  });
  const view = new ol.View({
    center: center,
    zoom: 6
  });
  this.map = new ol.Map({
    layers: [layer],
    interactions: [interaction],
    controls: [control],
    overlays: [overlay],
    view: view
  });
}

ngAfterViewInit() {
    this.map.setTarget(this.mapElement.nativeElement.id);
}

Answer 1

I think constructor might be too early to access it. Could you please try putting it in ngOnInit() or ngAfterViewInit() ?