feature-move-animation.js

import Feature from '../src/ol/Feature.js';
import Map from '../src/ol/Map.js';
import View from '../src/ol/View.js';
import Polyline from '../src/ol/format/Polyline.js';
import Point from '../src/ol/geom/Point.js';
import TileLayer from '../src/ol/layer/Tile.js';
import VectorLayer from '../src/ol/layer/Vector.js';
import BingMaps from '../src/ol/source/BingMaps.js';
import VectorSource from '../src/ol/source/Vector.js';
import CircleStyle from '../src/ol/style/Circle.js';
import Fill from '../src/ol/style/Fill.js';
import Icon from '../src/ol/style/Icon.js';
import Stroke from '../src/ol/style/Stroke.js';
import Style from '../src/ol/style/Style.js';

// This long string is placed here due to jsFiddle limitations.
// It is usually loaded with AJAX.
const polyline = [
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].join('');

const route = /** @type {module:ol/geom/LineString~LineString} */ (new Polyline({
  factor: 1e6
}).readGeometry(polyline, {
  dataProjection: 'EPSG:4326',
  featureProjection: 'EPSG:3857'
}));

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

const routeFeature = new Feature({
  type: 'route',
  geometry: route
});
const geoMarker = new Feature({
  type: 'geoMarker',
  geometry: new Point(routeCoords[0])
});
const startMarker = new Feature({
  type: 'icon',
  geometry: new Point(routeCoords[0])
});
const endMarker = new Feature({
  type: 'icon',
  geometry: new Point(routeCoords[routeLength - 1])
});

const 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,
      snapToPixel: false,
      fill: new Fill({color: 'black'}),
      stroke: new Stroke({
        color: 'white', width: 2
      })
    })
  })
};

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

const 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')];
  }
});

const center = [-5639523.95, -3501274.52];
const map = new Map({
  target: document.getElementById('map'),
  loadTilesWhileAnimating: true,
  view: new View({
    center: center,
    zoom: 10,
    minZoom: 2,
    maxZoom: 19
  }),
  layers: [
    new TileLayer({
      source: new BingMaps({
        imagerySet: 'AerialWithLabels',
        key: 'As1HiMj1PvLPlqc_gtM7AqZfBL8ZL3VrjaS3zIb22Uvb9WKhuJObROC-qUpa81U5'
      })
    }),
    vectorLayer
  ]
});

const moveFeature = function(event) {
  const vectorContext = event.vectorContext;
  const frameState = event.frameState;

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

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

    const currentPoint = new Point(routeCoords[index]);
    const feature = new Feature(currentPoint);
    vectorContext.drawFeature(feature, styles.geoMarker);
  }
  // tell OpenLayers to continue the postcompose 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);
    map.on('postcompose', 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
  const coord = ended ? routeCoords[routeLength - 1] : routeCoords[0];
  /** @type {module:ol/geom/Point~Point} */ (geoMarker.getGeometry())
    .setCoordinates(coord);
  //remove listener
  map.un('postcompose', moveFeature);
}

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