Box Selection

<!--
  说明：框选要素的中文示例，数据在页面内生成，可独立运行。
  核心逻辑：ol.interaction.DragBox + source.getFeaturesInExtent + 选中图层
  依赖：OpenLayers 10.3.1 · jsDelivr CDN
-->
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta name="robots" content="noindex,follow">
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>框选要素</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/ol@10.3.1/ol.css">
<style>
  html,body{height:100%;margin:0}
  body{display:flex;flex-direction:column;overflow:hidden;
       font:13px/1.6 -apple-system,"Segoe UI","PingFang SC",sans-serif}
  .bar{flex:0 0 auto;padding:8px 12px;background:#f6f7f9;border-bottom:1px solid #e3e6ea;
       display:flex;gap:10px;align-items:center;flex-wrap:wrap;font-size:12px;color:#58606e}
  .bar label{display:flex;gap:5px;align-items:center;cursor:pointer}
  .bar button{font:inherit;padding:3px 9px;border:1px solid #c9ced6;background:#fff;
       border-radius:5px;cursor:pointer;color:#333}
  .bar button:hover{background:#eef2f8}
  .bar input[type=range]{width:110px;vertical-align:middle}
  .bar input[type=text]{font:inherit;padding:2px 6px;border:1px solid #c9ced6;border-radius:4px}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3;position:relative}
  .panel{flex:0 0 auto;max-height:34%;overflow:auto;padding:8px 12px;font-size:12px;
       background:#fff;border-top:1px solid #e3e6ea;color:#3d4451}
  .panel pre{margin:0;font-family:Consolas,"Courier New",monospace;font-size:11px;
       white-space:pre-wrap;word-break:break-all;line-height:1.5}
  .ol-attribution{font-size:11px}

</style>
</head>
<body>
<div class="bar">
<span>按住 Shift 拖拽框选</span>
<button id="clear" type="button">清空选择</button>
<span id="info">选中 0 个</span>
</div>
<div id="map"></div>

<script src="https://cdn.jsdelivr.net/npm/ol@10.3.1/dist/ol.js"></script>
<script>
(function () {
  'use strict';

  if (typeof ol === 'undefined') {
    var errBox = document.getElementById('map');
    if (errBox) {
      errBox.innerHTML = '<div style="padding:20px;color:#b42318">OpenLayers 加载失败，请检查能否访问 cdn.jsdelivr.net</div>';
    }
    return;
  }

  var fromLonLat = ol.proj.fromLonLat;
  function rand(seed) {
    var v = Math.sin(seed * 12.9898) * 43758.5453;
    return v - Math.floor(v);
  }

  var names = ['朝阳', '海淀', '西城', '东城', '丰台', '石景山', '通州', '昌平'];
  var features = [];
  for (var i = 0; i < 48; i++) {
    var lon = 116.15 + rand(i + 1) * 0.62;
    var lat = 39.75 + rand(i + 21) * 0.34;
    features.push(new ol.Feature({
      geometry: new ol.geom.Point(fromLonLat([lon, lat])),
      name: names[i % names.length] + (i + 1)
    }));
  }

  var source = new ol.source.Vector({features: features});
  var selSource = new ol.source.Vector();

  var view = new ol.View({center: fromLonLat([116.4, 39.9]), zoom: 11});
  var map = new ol.Map({
    target: 'map',
    layers: [
      new ol.layer.Tile({source: new ol.source.XYZ({url: 'https://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer/tile/{z}/{y}/{x}', attributions: 'Tiles © Esri'})}),
      new ol.layer.Vector({
        source: source,
        style: new ol.style.Style({
          image: new ol.style.Circle({
            radius: 5,
            fill: new ol.style.Fill({color: '#1f5fd0'}),
            stroke: new ol.style.Stroke({color: '#ffffff', width: 1.5})
          })
        })
      }),
      new ol.layer.Vector({
        source: selSource,
        style: new ol.style.Style({
          image: new ol.style.Circle({
            radius: 8,
            fill: new ol.style.Fill({color: 'rgba(238,96,42,0.35)'}),
            stroke: new ol.style.Stroke({color: '#ee602a', width: 2})
          })
        })
      })
    ],
    view: view,
    controls: ol.control.defaults.defaults({attribution: false, zoom: true, rotate: false})
  });

  var dragBox = new ol.interaction.DragBox({
    condition: ol.events.condition.shiftKeyOnly
  });
  map.addInteraction(dragBox);

  var info = document.getElementById('info');

  dragBox.on('boxend', function () {
    var ext = dragBox.getGeometry().getExtent();
    var hit = source.getFeaturesInExtent(ext);
    selSource.clear();
    hit.forEach(function (f) { selSource.addFeature(f.clone()); });
    info.textContent = '选中 ' + hit.length + ' 个点 · 范围 ' +
      (ext[2] - ext[0]).toFixed(0) + ' × ' + (ext[3] - ext[1]).toFixed(0) + ' 米';
  });

  dragBox.on('boxstart', function () {
    info.textContent = '正在框选…';
  });

  document.getElementById('clear').addEventListener('click', function () {
    selSource.clear();
    info.textContent = '选中 0 个';
  });
})();
</script>
</body>
</html>