Modify Test

<!--
  示例：修改交互的实时反馈
  要点：modifystart/modifyend 记录编辑过程，逐次统计几何变化
  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>修改交互的实时反馈</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 button{padding:4px 10px;border:1px solid #d5dae2;background:#fff;border-radius:4px;cursor:pointer}
  .bar b{color:#16181d;font-weight:600}
  #log{font-family:ui-monospace,Menlo,Consolas,monospace;font-size:11px}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <span>顶点 <b id="vn">—</b></span>
  <span>长度 <b id="len">—</b></span>
  <span>修改次数 <b id="cnt">0</b></span>
  <span id="log">等待编辑</span>
  <button id="reset">复位</button>
</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 base = [
    [116.30, 39.90], [116.355, 39.945], [116.415, 39.918],
    [116.470, 39.952], [116.520, 39.900]
  ].map(function (c) { return fromLonLat(c); });

  var line = new ol.Feature({ geometry: new ol.geom.LineString(base.slice()) });
  line.setStyle(new ol.style.Style({
    stroke: new ol.style.Stroke({ color: '#1f5fd0', width: 3 }),
    image: new ol.style.Circle({
      radius: 5,
      fill: new ol.style.Fill({ color: '#ffffff' }),
      stroke: new ol.style.Stroke({ color: '#1f5fd0', width: 2 })
    })
  }));

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

  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([116.41, 39.92]), zoom: 12 }),
    controls: ol.control.defaults.defaults({ rotate: false })
  });

  var modify = new ol.interaction.Modify({ source: source, pixelTolerance: 10 });
  map.addInteraction(modify);

  var count = 0;
  var startCoords = null;

  function stats() {
    var g = line.getGeometry();
    var coords = g.getCoordinates();
    document.getElementById('vn').textContent = coords.length;
    document.getElementById('len').textContent = (ol.sphere.getLength(g) / 1000).toFixed(4) + ' km';
    return coords;
  }

  modify.on('modifystart', function () {
    startCoords = line.getGeometry().getCoordinates().slice();
    document.getElementById('log').textContent = '开始拖动…';
  });

  modify.on('modifyend', function () {
    count++;
    document.getElementById('cnt').textContent = count;

    var coords = stats();
    /* 对比拖动前后，找出真正移动的顶点索引 */
    var moved = [];
    coords.forEach(function (c, i) {
      var s = startCoords[i];
      if (!s || c[0] !== s[0] || c[1] !== s[1]) moved.push(i);
    });

    var lonlat = moved.length
      ? ol.proj.toLonLat(coords[moved[moved.length - 1]])
      : null;

    document.getElementById('log').textContent = lonlat
      ? '顶点 #' + moved.join(',#') + ' 移到 ' + lonlat[0].toFixed(5) + ', ' + lonlat[1].toFixed(5)
      : '这次没有顶点位置变化';
  });

  document.getElementById('reset').addEventListener('click', function () {
    line.getGeometry().setCoordinates(base.slice());
    count = 0;
    document.getElementById('cnt').textContent = '0';
    document.getElementById('log').textContent = '已复位';
    stats();
  });

  stats();
})();
</script>
</body>
</html>