Map is gray or white when I leave my page

Ionic Framework ionic-v3
1

Map is gray or white when I leave my page.
My problem is this: My map loads well but if I go to the menu or see other options when I return to the map, no load remains gray or white.
I solve it with the getCurrentPosition () what happens is that I occupy my location updated since it is an uber type service … so I do it with the watchPosition () and that’s where the map does not load me
Investigating I saw that the solution is to make a detector to the mosaic loading event but I have no idea what it is or how it is done if somebody guides me I thank you


ionViewDidLoad(){
  if(this.ubiProv.solicitud){
    this.agregarMarcas();
  }else {
    //this.initializeMap();
    this.watchCurrentPosition()
    //this.tryGeolocation();
  }
}

watchCurrentPosition() {
  navigator.geolocation.watchPosition(
    (position)=> {
      let pos = {
        lat: position.coords.latitude,
        lng: position.coords.longitude
      };
        let options = {
          center: new google.maps.LatLng(position.coords.latitude, position.coords.longitude),
          zoom: 16,
          mapTypeId: google.maps.MapTypeId.ROADMAP
        }
        this.map = new google.maps.Map(document.getElementById("map"), options);

        let marker = new google.maps.Marker({
          map: this.map,
          icon: new google.maps.MarkerImage('//maps.gstatic.com/mapfiles/mobile/mobileimgs2.png',
            new google.maps.Size(22, 22),
            new google.maps.Point(0, 18),
            new google.maps.Point(11, 11)),
          position: pos
        });
        let nombre = this.userProv.nombre
        let content = nombre;
        this.addInfoWindow(marker, content);
    },
    (error) => {
        console.log(error);
    });
}