Решено! Я добавил onChange, как предложил @webdevius:
Добавлено onChange в HTML-код моей панели
<div class="filter-multiselect">
<p-multiSelect [options]="items"
[(ngModel)]="itemsSelected"
styleClass="multiSelect"
[defaultLabel]="labelComponent"
(onPanelShow)="handlePanelShow()"
(onPanelHide)="handlePanelHide()"
(onChange)="filtersApply()"
panelStyleClass="panelStyleClassCustom"
[ngClass]="isOpen ? 'multi-select-open' : '' "
[maxSelectedLabels]="0">
<ng-template let-element let-i="index" pTemplate="item">
<div class="ui-multiselect-item-text">{{element.label}}</div>
</ng-template>
</p-multiSelect>
</div>
и излучать при выборе фильтра (теперь не зависит, открыта ли панель или нет)
import { Component, OnInit, ViewEncapsulation, Input, ElementRef, EventEmitter, Output } from '@angular/core';
import { MultiselectBaseModel } from '../app-models/MultiselectBaseModel';
@Component({
selector: 'app-filter-multiselect',
templateUrl: './filter-multiselect.component.html',
styleUrls: ['./filter-multiselect.component.less'],
encapsulation: ViewEncapsulation.None
})
export class FilterMultiselectComponent implements OnInit {
@Input() labelComponent: string;
@Input() items: MultiselectBaseModel[];
@Input() itemsSelected: MultiselectBaseModel[];
@Output() closeMultiselectEventHandler: EventEmitter<any> = new EventEmitter();
isOpen = false;
constructor(public el: ElementRef) { }
ngOnInit() {}
handlePanelShow() {
this.isOpen = true;
}
handlePanelHide() {
this.isOpen = false;
}
filtersApply() {
this.closeMultiselectEventHandler.emit(this.itemsSelected);
}
handleClickMultiSelect(event) {
}
}