Draw

<!--
  示例：绘制交互
  要点：ol.interaction.Draw 三种几何类型切换，Modify 编辑已有顶点
  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>绘制交互</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:12px;align-items:center;font-size:12px;color:#58606e;flex-wrap:wrap}
  .bar select,.bar button{font:inherit;font-size:12px;padding:4px 8px;border:1px solid #ccd1d9;
       border-radius:4px;background:#fff;color:#16181d;cursor:pointer}
  .bar label{display:flex;gap:5px;align-items:center;cursor:pointer}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <label>类型
    <select id="type">
      <option value="Point">点</option>
      <option value="LineString" selected>线</option>
      <option value="Polygon">面</option>
    </select>
  </label>
  <label><input type="checkbox" id="modify"> 可拖动顶点</label>
  <button id="clear">清空</button>
  <span id="info">在线类型下单击落点，双击结束</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') {
    document.getElementById('map').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;

  var drawSource = new ol.source.Vector();

  var drawLayer = new ol.layer.Vector({
    source: drawSource,
    style: new ol.style.Style({
      fill: new ol.style.Fill({ color: 'rgba(31,95,208,0.15)' }),
      stroke: new ol.style.Stroke({ color: '#1f5fd0', width: 2 }),
      image: new ol.style.Circle({
        radius: 5,
        fill: new ol.style.Fill({ color: '#1f5fd0' }),
        stroke: new ol.style.Stroke({ color: '#ffffff', width: 2 })
      })
    })
  });

  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'}) }),
      drawLayer
    ],
    view: new ol.View({
      center: fromLonLat([116.400, 39.915]),
      zoom: 12
    })
  });

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

  /* Modify 只对已有顶点生效，单独控制开关，避免和绘制争抢鼠标 */
  var modify = new ol.interaction.Modify({ source: drawSource, active: false });
  map.addInteraction(modify);

  function startDraw(type) {
    if (currentDraw) {
      map.removeInteraction(currentDraw);
    }

    currentDraw = new ol.interaction.Draw({
      source: drawSource,
      type: type
    });

    currentDraw.on('drawend', function (evt) {
      var geom = evt.feature.getGeometry();
      var count = 0;

      if (type === 'LineString') {
        count = geom.getCoordinates().length;
      } else if (type === 'Polygon') {
        count = geom.getCoordinates()[0].length - 1;
      }

      info.textContent = type === 'Point'
        ? '已添加点，投影坐标 ' + geom.getCoordinates()[0].toFixed(0)
        : '已完成 ' + type + '，顶点数 ' + count;
    });

    map.addInteraction(currentDraw);
  }

  startDraw('LineString');

  document.getElementById('type').addEventListener('change', function () {
    startDraw(this.value);
    info.textContent = '切换为 ' + this.options[this.selectedIndex].text + '，单击开始绘制';
  });

  document.getElementById('modify').addEventListener('change', function () {
    modify.setActive(this.checked);
    currentDraw.setActive(!this.checked);
    info.textContent = this.checked ? '拖动已有顶点调整形状' : '已回到绘制模式';
  });

  document.getElementById('clear').addEventListener('click', function () {
    drawSource.clear();
    info.textContent = '已清空全部要素';
  });
})();
</script>
</body>
</html>