Vector Layer Hit Detection

矢量图层命中检测

vector 86 geojson 11 click 1 hover 2 hitdetection 1

在带有保护状态的生态区矢量图层上命中检测的示例。

生态区数据从 GeoJSON 文件加载。通过图层的 getFeatures() 方法在悬停和点击时检索要素信息。对于矢量图层，此函数仅解析为最顶层要素的数组。它使用高效的命中检测算法，但以精度为代价。当性能不是问题时，如需像素级精确的命中检测，请使用地图的 getFeaturesAtPixel() 或 forEachFeatureAtPixel() 方法。

main.js

import Map from 'ol/Map.js';
import View from 'ol/View.js';
import GeoJSON from 'ol/format/GeoJSON.js';
import VectorLayer from 'ol/layer/Vector.js';
import VectorSource from 'ol/source/Vector.js';

const vectorLayer = new VectorLayer({
  background: '#1a2b39',
  source: new VectorSource({
    url: 'https://openlayers.org/data/vector/ecoregions.json',
    format: new GeoJSON(),
  }),
  style: {
    'fill-color': ['string', ['get', 'COLOR_NNH'], '#eee'],
  },
});

const map = new Map({
  layers: [vectorLayer],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 1,
  }),
});

const featureOverlay = new VectorLayer({
  source: new VectorSource(),
  map: map,
  style: {
    'stroke-color': 'rgba(255, 255, 255, 0.7)',
    'stroke-width': 2,
  },
});

let highlight;
const displayFeatureInfo = function (pixel) {
  vectorLayer.getFeatures(pixel).then(function (features) {
    const feature = features.length ? features[0] : undefined;
    const info = document.getElementById('info');
    if (features.length) {
      info.innerHTML = feature.get('ECO_NAME') + ': ' + feature.get('NNH_NAME');
    } else {
      info.innerHTML = '&nbsp;';
    }

    if (feature !== highlight) {
      if (highlight) {
        featureOverlay.getSource().removeFeature(highlight);
      }
      if (feature) {
        featureOverlay.getSource().addFeature(feature);
      }
      highlight = feature;
    }
  });
};

map.on('pointermove', function (evt) {
  if (evt.dragging) {
    return;
  }
  displayFeatureInfo(evt.pixel);
});

map.on('click', function (evt) {
  displayFeatureInfo(evt.pixel);
});

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Vector Layer Hit Detection</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>
    <div id="info">&nbsp;</div>

    <script type="module" src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "hitdetect-vector",
  "dependencies": {
    "ol": "10.9.0"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}