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Custom Interactions

drag4 feature11 vector63 editing2 custom5 interaction4

Example of a custom interaction.

This example demonstrates creating a custom interaction by subclassing ol/interaction/Pointer. Note that the built in interaction ol/interaction/Translate might be a better option for moving features.

main.js
import 'ol/ol.css';
import Feature from 'ol/Feature';
import Map from 'ol/Map';
import View from 'ol/View';
import {Fill, Icon, Stroke, Style} from 'ol/style';
import {LineString, Point, Polygon} from 'ol/geom';
import {
  Pointer as PointerInteraction,
  defaults as defaultInteractions,
} from 'ol/interaction';
import {TileJSON, Vector as VectorSource} from 'ol/source';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer';

class Drag extends PointerInteraction {
  constructor() {
    super({
      handleDownEvent: handleDownEvent,
      handleDragEvent: handleDragEvent,
      handleMoveEvent: handleMoveEvent,
      handleUpEvent: handleUpEvent,
    });

    /**
     * @type {import("../src/ol/coordinate.js").Coordinate}
     * @private
     */
    this.coordinate_ = null;

    /**
     * @type {string|undefined}
     * @private
     */
    this.cursor_ = 'pointer';

    /**
     * @type {Feature}
     * @private
     */
    this.feature_ = null;

    /**
     * @type {string|undefined}
     * @private
     */
    this.previousCursor_ = undefined;
  }
}

/**
 * @param {import("../src/ol/MapBrowserEvent.js").default} evt Map browser event.
 * @return {boolean} `true` to start the drag sequence.
 */
function handleDownEvent(evt) {
  const map = evt.map;

  const feature = map.forEachFeatureAtPixel(evt.pixel, function (feature) {
    return feature;
  });

  if (feature) {
    this.coordinate_ = evt.coordinate;
    this.feature_ = feature;
  }

  return !!feature;
}

/**
 * @param {import("../src/ol/MapBrowserEvent.js").default} evt Map browser event.
 */
function handleDragEvent(evt) {
  const deltaX = evt.coordinate[0] - this.coordinate_[0];
  const deltaY = evt.coordinate[1] - this.coordinate_[1];

  const geometry = this.feature_.getGeometry();
  geometry.translate(deltaX, deltaY);

  this.coordinate_[0] = evt.coordinate[0];
  this.coordinate_[1] = evt.coordinate[1];
}

/**
 * @param {import("../src/ol/MapBrowserEvent.js").default} evt Event.
 */
function handleMoveEvent(evt) {
  if (this.cursor_) {
    const map = evt.map;
    const feature = map.forEachFeatureAtPixel(evt.pixel, function (feature) {
      return feature;
    });
    const element = evt.map.getTargetElement();
    if (feature) {
      if (element.style.cursor != this.cursor_) {
        this.previousCursor_ = element.style.cursor;
        element.style.cursor = this.cursor_;
      }
    } else if (this.previousCursor_ !== undefined) {
      element.style.cursor = this.previousCursor_;
      this.previousCursor_ = undefined;
    }
  }
}

/**
 * @return {boolean} `false` to stop the drag sequence.
 */
function handleUpEvent() {
  this.coordinate_ = null;
  this.feature_ = null;
  return false;
}

const pointFeature = new Feature(new Point([0, 0]));

const lineFeature = new Feature(
  new LineString([
    [-1e7, 1e6],
    [-1e6, 3e6],
  ])
);

const polygonFeature = new Feature(
  new Polygon([
    [
      [-3e6, -1e6],
      [-3e6, 1e6],
      [-1e6, 1e6],
      [-1e6, -1e6],
      [-3e6, -1e6],
    ],
  ])
);

const key =
  'Your Mapbox access token from https://mapbox.com/ here';

const map = new Map({
  interactions: defaultInteractions().extend([new Drag()]),
  layers: [
    new TileLayer({
      source: new TileJSON({
        url:
          'https://a.tiles.mapbox.com/v4/aj.1x1-degrees.json?secure&access_token=' +
          key,
      }),
    }),
    new VectorLayer({
      source: new VectorSource({
        features: [pointFeature, lineFeature, polygonFeature],
      }),
      style: new Style({
        image: new Icon({
          anchor: [0.5, 46],
          anchorXUnits: 'fraction',
          anchorYUnits: 'pixels',
          opacity: 0.95,
          src: 'data/icon.png',
        }),
        stroke: new Stroke({
          width: 3,
          color: [255, 0, 0, 1],
        }),
        fill: new Fill({
          color: [0, 0, 255, 0.6],
        }),
      }),
    }),
  ],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 2,
  }),
});
index.html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Custom Interactions</title>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep"></script>
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v3/polyfill.min.js?features=fetch,requestAnimationFrame,Element.prototype.classList,URL,TextDecoder,Number.isInteger"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <script src="main.js"></script>
  </body>
</html>
package.json
{
  "name": "custom-interactions",
  "dependencies": {
    "ol": "6.6.1"
  },
  "devDependencies": {
    "parcel": "^2.0.0-beta.1"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}