//in HTML

<input

  #autoCompleteInput //it is the selector used in component

  type="text"

  class="form-control"

  matInput

  [matAutocomplete]="auto"

  formControlName="country"

  (input)="filterCountries($event.target.value)"

/>

​

//in component

@ViewChild('autoCompleteInput', { read: MatAutocompleteTrigger, static: false })

autoComplete: MatAutocompleteTrigger;

​

ngOnInit(): void {

    window.addEventListener('scroll', this.scrollEvent, true);

}

​

scrollEvent = (event: any): void => {

    if(this.autoComplete.panelOpen)

      // this.autoComplete.closePanel(); //you can also close the panel 

      this.autoComplete.updatePosition();

};