矢量瓦片选中

在矢量瓦片中选中图形要素.

在地图上点击高亮已经渲染的矢量瓦片图形要素。点击地图上空白的地方（海洋）来重置选中的对象。通过改变触发动作的类型（"Multi Select"）可以连续选中多个图形要素。当选中单个悬浮时（"Single Select on hover"），鼠标悬浮在图形要素上时会高亮显示。

当选中图层配置 renderMode: 'vector' 参数后，在频繁重绘时性能会更好，即在选择 "Single Select on hover" 操作的时候。

main.js

import MVT from 'ol/format/MVT.js';
import Map from 'ol/Map.js';
import VectorTileLayer from 'ol/layer/VectorTile.js';
import VectorTileSource from 'ol/source/VectorTile.js';
import View from 'ol/View.js';
import {Fill, Stroke, Style} from 'ol/style.js';

// lookup for selection objects
let selection = {};

const country = new Style({
  stroke: new Stroke({
    color: 'gray',
    width: 1,
  }),
  fill: new Fill({
    color: 'rgba(20,20,20,0.9)',
  }),
});
const selectedCountry = new Style({
  stroke: new Stroke({
    color: 'rgba(200,20,20,0.8)',
    width: 2,
  }),
  fill: new Fill({
    color: 'rgba(200,20,20,0.4)',
  }),
});

const vtLayer = new VectorTileLayer({
  declutter: true,
  source: new VectorTileSource({
    maxZoom: 15,
    format: new MVT({
      idProperty: 'iso_a3',
    }),
    url:
      'https://ahocevar.com/geoserver/gwc/service/tms/1.0.0/' +
      'ne:ne_10m_admin_0_countries@EPSG%3A900913@pbf/{z}/{x}/{-y}.pbf',
  }),
  style: country,
});

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

// Selection
const selectionLayer = new VectorTileLayer({
  map: map,
  renderMode: 'vector',
  source: vtLayer.getSource(),
  style: function (feature) {
    if (feature.getId() in selection) {
      return selectedCountry;
    }
  },
});

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

map.on(['click', 'pointermove'], function (event) {
  if (
    (selectElement.value === 'singleselect-hover' &&
      event.type !== 'pointermove') ||
    (selectElement.value !== 'singleselect-hover' &&
      event.type === 'pointermove')
  ) {
    return;
  }
  vtLayer.getFeatures(event.pixel).then(function (features) {
    if (!features.length) {
      selection = {};
      selectionLayer.changed();
      return;
    }
    const feature = features[0];
    if (!feature) {
      return;
    }
    const fid = feature.getId();

    if (selectElement.value.startsWith('singleselect')) {
      selection = {};
    }
    // add selected feature to lookup
    selection[fid] = feature;

    selectionLayer.changed();
  });
});

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Vector Tile Selection</title>
    <link rel="stylesheet" href="node_modules/ol/ol.css">
    <style>
      .map {
        width: 100%;
        height: 400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <form>
      <label for="type">Action type &nbsp;</label>
      <select id="type">
        <option value="singleselect" selected>Single Select</option>
        <option value="multiselect">Multi Select</option>
        <option value="singleselect-hover">Single Select on hover</option>
      </select>
    </form>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="./resources/elm-pep.js"></script>
    <script type="module" src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "vector-tile-selection",
  "dependencies": {
    "ol": "7.3.0"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}