Marker Animation

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index.jsimport 'ol/ol.css';
import Feature from 'ol/Feature';
import Map from 'ol/Map';
import View from 'ol/View';
import Polyline from 'ol/format/Polyline';
import Point from 'ol/geom/Point';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer';
import BingMaps from 'ol/source/BingMaps';
import VectorSource from 'ol/source/Vector';
import {Circle as CircleStyle, Fill, Icon, Stroke, Style} from 'ol/style';
import {getVectorContext} from 'ol/render';

// This long string is placed here due to jsFiddle limitations.
// It is usually loaded with AJAX.
var polyline = [
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var route = /** @type {import("../src/ol/geom/LineString.js").default} */ (new Polyline({
  factor: 1e6
}).readGeometry(polyline, {
  dataProjection: 'EPSG:4326',
  featureProjection: 'EPSG:3857'
}));

var routeCoords = route.getCoordinates();
var routeLength = routeCoords.length;

var routeFeature = new Feature({
  type: 'route',
  geometry: route
});
var geoMarker = /** @type Feature<import("../src/ol/geom/Point").default> */(new Feature({
  type: 'geoMarker',
  geometry: new Point(routeCoords[0])
}));
var startMarker = new Feature({
  type: 'icon',
  geometry: new Point(routeCoords[0])
});
var endMarker = new Feature({
  type: 'icon',
  geometry: new Point(routeCoords[routeLength - 1])
});

var styles = {
  'route': new Style({
    stroke: new Stroke({
      width: 6, color: [237, 212, 0, 0.8]
    })
  }),
  'icon': new Style({
    image: new Icon({
      anchor: [0.5, 1],
      src: 'data/icon.png'
    })
  }),
  'geoMarker': new Style({
    image: new CircleStyle({
      radius: 7,
      fill: new Fill({color: 'black'}),
      stroke: new Stroke({
        color: 'white', width: 2
      })
    })
  })
};

var animating = false;
var speed, now;
var speedInput = document.getElementById('speed');
var startButton = document.getElementById('start-animation');

var vectorLayer = new VectorLayer({
  source: new VectorSource({
    features: [routeFeature, geoMarker, startMarker, endMarker]
  }),
  style: function(feature) {
    // hide geoMarker if animation is active
    if (animating && feature.get('type') === 'geoMarker') {
      return null;
    }
    return styles[feature.get('type')];
  }
});

var center = [-5639523.95, -3501274.52];
var map = new Map({
  target: document.getElementById('map'),
  view: new View({
    center: center,
    zoom: 10,
    minZoom: 2,
    maxZoom: 19
  }),
  layers: [
    new TileLayer({
      source: new BingMaps({
        imagerySet: 'AerialWithLabelsOnDemand',
        key: 'Your Bing Maps Key from http://www.bingmapsportal.com/ here'
      })
    }),
    vectorLayer
  ]
});

var moveFeature = function(event) {
  var vectorContext = getVectorContext(event);
  var frameState = event.frameState;

  if (animating) {
    var elapsedTime = frameState.time - now;
    // here the trick to increase speed is to jump some indexes
    // on lineString coordinates
    var index = Math.round(speed * elapsedTime / 1000);

    if (index >= routeLength) {
      stopAnimation(true);
      return;
    }

    var currentPoint = new Point(routeCoords[index]);
    var feature = new Feature(currentPoint);
    vectorContext.drawFeature(feature, styles.geoMarker);
  }
  // tell OpenLayers to continue the postrender animation
  map.render();
};

function startAnimation() {
  if (animating) {
    stopAnimation(false);
  } else {
    animating = true;
    now = new Date().getTime();
    speed = speedInput.value;
    startButton.textContent = 'Cancel Animation';
    // hide geoMarker
    geoMarker.setStyle(null);
    // just in case you pan somewhere else
    map.getView().setCenter(center);
    vectorLayer.on('postrender', moveFeature);
    map.render();
  }
}


/**
 * @param {boolean} ended end of animation.
 */
function stopAnimation(ended) {
  animating = false;
  startButton.textContent = 'Start Animation';

  // if animation cancelled set the marker at the beginning
  var coord = ended ? routeCoords[routeLength - 1] : routeCoords[0];
  var geometry = geoMarker.getGeometry();
  geometry.setCoordinates(coord);
  //remove listener
  vectorLayer.un('postrender', moveFeature);
}

startButton.addEventListener('click', startAnimation, false);