Edit

Marker Animation

animation5 feature11 postrender1 polyline1 maptiler24

Demonstrates how to move a feature along a line.

This example shows how to use postrender events and a vector context to animate a marker feature along a line. In this example an encoded polyline is being used.

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

var key = 'Get your own API key at https://www.maptiler.com/cloud/';
var attributions =
  '<a href="https://www.maptiler.com/copyright/" target="_blank">&copy; MapTiler</a> ' +
  '<a href="https://www.openstreetmap.org/copyright" target="_blank">&copy; OpenStreetMap contributors</a>';

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 XYZ({
        attributions: attributions,
        url: 'https://api.maptiler.com/maps/hybrid/{z}/{x}/{y}.jpg?key=' + key,
        tileSize: 512,
      }),
    }) ],
});

// The polyline string is read from a JSON similiar to those returned
// by directions APIs such as Openrouteservice and Mapbox.
fetch('data/polyline/route.json').then(function (response) {
  response.json().then(function (result) {
    var polyline = result.routes[0].geometry;

    var route = new Polyline({
      factor: 1e6,
    }).readGeometry(polyline, {
      dataProjection: 'EPSG:4326',
      featureProjection: 'EPSG:3857',
    });

    var routeFeature = new Feature({
      type: 'route',
      geometry: route,
    });
    var geoMarker = new Feature({
      type: 'geoMarker',
      geometry: new Point(route.getCoordinateAt(0)),
    });
    var startMarker = new Feature({
      type: 'icon',
      geometry: new Point(route.getCoordinateAt(0)),
    });
    var endMarker = new Feature({
      type: 'icon',
      geometry: new Point(route.getCoordinateAt(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 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')];
      },
    });

    map.addLayer(vectorLayer);

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

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

      if (animating) {
        var elapsedTime = frameState.time - startTime;
        var distance = (speed * elapsedTime) / 1e6;

        if (distance >= 1) {
          stopAnimation(true);
          return;
        }

        var currentPoint = new Point(route.getCoordinateAt(distance));
        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;
        startTime = new Date().getTime();
        speed = speedInput.value;
        startButton.textContent = 'Cancel Animation';
        // hide geoMarker
        geoMarker.changed();
        // just in case you pan somewhere else
        map.getView().setCenter(center);
        vectorLayer.on('postrender', moveFeature);
        map.render();
      }
    }

    function stopAnimation(ended) {
      animating = false;
      startButton.textContent = 'Start Animation';

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

    startButton.addEventListener('click', startAnimation, false);
  });
});
index.html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Marker Animation</title>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <label for="speed">
      speed:&nbsp;
      <input id="speed" type="range" min="10" max="999" step="10" value="60">
    </label>
    <button id="start-animation">Start Animation</button>
    <script src="main.js"></script>
  </body>
</html>
package.json
{
  "name": "feature-move-animation",
  "dependencies": {
    "ol": "6.5.0"
  },
  "devDependencies": {
    "parcel": "^2.0.0-beta.1"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}