mdq: MediaQueryList;
  mediaQueryListener:()=>void;

  constructor( changeDetectorRef: ChangeDetectorRef, media: MediaMatcher ) {
    this.mdq = media.matchMedia('(max-width: 992px)');
    this.mediaQueryListener = () => changeDetectorRef.detectChanges();
    this.mdq.addListener(this.mediaQueryListener);
  }