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Select Features

发布于 2022-11-30 23:36:05 字数 5843 浏览 0 评论 0 收藏 0

Example of using the Select interaction.

Choose between Single-click, Click, Hover and Alt+Click as the event type for selection in the combobox below. When using Single-click or Click you can hold the Shift key to toggle the feature in the selection.

Note: when Single-click is used double-clicks won't select features. This in contrast to Click, where a double-click will both select the feature and zoom the map (because of the DoubleClickZoom interaction). Note that Single-click is less responsive than Click because of the delay it uses to detect double-clicks.

In this example, a listener is registered for the Select interaction's select event in order to update the selection status above.

main.js

import 'ol/ol.css';
import GeoJSON from 'ol/format/GeoJSON';
import Map from 'ol/Map';
import OSM from 'ol/source/OSM';
import Select from 'ol/interaction/Select';
import VectorSource from 'ol/source/Vector';
import View from 'ol/View';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer';
import {altKeyOnly, click, pointerMove} from 'ol/events/condition';

const raster = new TileLayer({
  source: new OSM(),
});

const vector = new VectorLayer({
  source: new VectorSource({
    url: 'data/geojson/countries.geojson',
    format: new GeoJSON(),
  }),
});

const map = new Map({
  layers: [raster, vector],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 2,
  }),
});

let select = null; // ref to currently selected interaction

// select interaction working on "singleclick"
const selectSingleClick = new Select();

// select interaction working on "click"
const selectClick = new Select({
  condition: click,
});

// select interaction working on "pointermove"
const selectPointerMove = new Select({
  condition: pointerMove,
});

const selectAltClick = new Select({
  condition: function (mapBrowserEvent) {
    return click(mapBrowserEvent) && altKeyOnly(mapBrowserEvent);
  },
});

const selectElement = document.getElementById('type');

const changeInteraction = function () {
  if (select !== null) {
    map.removeInteraction(select);
  }
  const value = selectElement.value;
  if (value == 'singleclick') {
    select = selectSingleClick;
  } else if (value == 'click') {
    select = selectClick;
  } else if (value == 'pointermove') {
    select = selectPointerMove;
  } else if (value == 'altclick') {
    select = selectAltClick;
  } else {
    select = null;
  }
  if (select !== null) {
    map.addInteraction(select);
    select.on('select', function (e) {
      document.getElementById('status').innerHTML =
        '&nbsp;' +
        e.target.getFeatures().getLength() +
        ' selected features (last operation selected ' +
        e.selected.length +
        ' and deselected ' +
        e.deselected.length +
        ' features)';
    });
  }
};

/**
 * onchange callback on the select element.
 */
selectElement.onchange = changeInteraction;
changeInteraction();

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Select Features</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="./resources/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>
    <form class="form-inline">
      <label for="type">Action type &nbsp;</label>
      <select id="type" class="form-control">
        <option value="click" selected>Click</option>
        <option value="singleclick">Single-click</option>
        <option value="pointermove">Hover</option>
        <option value="altclick">Alt+Click</option>
        <option value="none">None</option>
      </select>
      <span id="status">&nbsp;0 selected features</span>
    </form>
    <script src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "select-features",
  "dependencies": {
    "ol": "7.1.0"
  },
  "devDependencies": {
    "parcel": "^2.0.0-beta.1"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}

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