Modify Features

<!--
  示例：修改要素
  要点：Modify 交互拖动顶点，insertVertexCondition 控制能否增删节点
  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>修改要素</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;color:#16181d}
  .bar{flex:0 0 auto;padding:8px 12px;background:#f6f7f9;border-bottom:1px solid #e3e6ea;
       display:flex;gap:14px;align-items:center;font-size:12px;color:#58606e;flex-wrap:wrap}
  .bar label{display:flex;gap:5px;align-items:center;cursor:pointer}
  .bar b{color:#16181d;font-weight:600}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <label><input type="checkbox" id="cbInsert" checked> 允许增删顶点</label>
  <span>顶点数 <b id="vn">—</b> / 面积 <b id="area">—</b></span>
  <span id="hint">拖动顶点或边中点</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 (!window.ol) {
    document.getElementById('map').textContent = 'OpenLayers 加载失败，请检查 cdn.jsdelivr.net 是否可访问';
    return;
  }
  var fromLonLat = ol.proj.fromLonLat;

  var ring = [
    [116.345, 39.935], [116.430, 39.945], [116.470, 39.900],
    [116.420, 39.862], [116.352, 39.878], [116.345, 39.935]
  ].map(function (c) { return fromLonLat(c); });

  var polygon = new ol.Feature({ geometry: new ol.geom.Polygon([ring]) });

  var style = new ol.style.Style({
    fill: new ol.style.Fill({ color: 'rgba(31,95,208,0.16)' }),
    stroke: new ol.style.Stroke({ color: '#1f5fd0', width: 2 }),
    image: new ol.style.Circle({
      radius: 5,
      fill: new ol.style.Fill({ color: '#ffffff' }),
      stroke: new ol.style.Stroke({ color: '#1f5fd0', width: 2 })
    })
  });
  polygon.setStyle(style);

  var source = new ol.source.Vector({ features: [polygon] });

  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 })],
    view: new ol.View({ center: fromLonLat([116.405, 39.905]), zoom: 12 }),
    controls: ol.control.defaults.defaults({ rotate: false })
  });

  var insertAllowed = true;

  var modify = new ol.interaction.Modify({
    source: source,
    insertVertexCondition: function () { return insertAllowed; }
  });

  map.addInteraction(modify);

  function report() {
    var coords = polygon.getGeometry().getCoordinates()[0];
    /* 闭合环首尾同点，顶点数要减 1 */
    document.getElementById('vn').textContent = Math.max(0, coords.length - 1);
    document.getElementById('area').textContent =
      (ol.sphere.getArea(polygon.getGeometry()) / 1e6).toFixed(3) + ' km²';
  }

  modify.on('modifyend', report);
  report();

  document.getElementById('cbInsert').addEventListener('change', function () {
    insertAllowed = this.checked;
    document.getElementById('hint').textContent = insertAllowed
      ? '拖动顶点或边中点'
      : '只能移动已有顶点，边中点不再响应';
  });
})();
</script>
</body>
</html>