Layer Zoom Limits

<!--
  示例：图层缩放范围 — OpenLayers layer-zoom-limits
  核心逻辑：给每个图层设置 minZoom / maxZoom，缩放时由 OpenLayers 自动决定可见性
  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>图层缩放范围</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:14px;align-items:center;font-size:12px;color:#58606e;flex-wrap:wrap}
  .bar input[type=range]{width:200px}
  .tag{display:inline-block;padding:1px 7px;border-radius:9px;font-size:11px;
       background:#e9ecf1;color:#8a919e}
  .tag.on{background:#1f5fd0;color:#fff}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <label>缩放 <input type="range" id="zoom" min="4" max="16" step="1" value="12"><b id="zoomVal">12</b></label>
  <span id="tagCity" class="tag">城区 10–14</span>
  <span id="tagRing" class="tag">环路 8–12</span>
  <span id="tagRegion" class="tag">区域 4–9</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;
  }

  function ring(coords) {
    return new ol.geom.Polygon([coords.concat([coords[0]])])
      .transform('EPSG:4326', 'EPSG:3857');
  }

  /* 三层：区域面、环路、城区点，各自只在一定缩放范围内可见 */
  var regionLayer = new ol.layer.Vector({
    source: new ol.source.Vector({
      features: [new ol.Feature({
        geometry: ring([[115.9, 39.5], [117.0, 39.5], [117.0, 40.3],
          [115.9, 40.3], [115.9, 39.5]])
      })]
    }),
    style: new ol.style.Style({
      fill: new ol.style.Fill({ color: 'rgba(47,158,68,0.18)' }),
      stroke: new ol.style.Stroke({ color: '#2f9e44', width: 2, lineDash: [10, 6] })
    }),
    minZoom: 4,
    maxZoom: 9
  });

  var ringLayer = new ol.layer.Vector({
    source: new ol.source.Vector({
      features: [new ol.Feature({
        geometry: ring([[116.25, 39.85], [116.55, 39.85], [116.55, 40.02],
          [116.25, 40.02], [116.25, 39.85]])
      })]
    }),
    style: new ol.style.Style({
      fill: new ol.style.Fill({ color: 'rgba(232,89,12,0.12)' }),
      stroke: new ol.style.Stroke({ color: '#e8590c', width: 3 })
    }),
    minZoom: 8,
    maxZoom: 12
  });

  var cityFeatures = [
    [116.391, 39.907, '中心城区'],
    [116.461, 39.909, '国贸'],
    [116.352, 39.905, '西单']
  ].map(function (p) {
    return new ol.Feature({
      geometry: new ol.geom.Point(ol.proj.fromLonLat([p[0], p[1]])),
      name: p[2]
    });
  });

  var cityLayer = new ol.layer.Vector({
    source: new ol.source.Vector({ features: cityFeatures }),
    style: function (f) {
      return new ol.style.Style({
        image: new ol.style.Circle({
          radius: 5,
          fill: new ol.style.Fill({ color: '#1f5fd0' })
        }),
        text: new ol.style.Text({
          text: f.get('name'),
          offsetY: -13,
          font: '500 12px sans-serif',
          fill: new ol.style.Fill({ color: '#16181d' }),
          stroke: new ol.style.Stroke({ color: '#fff', width: 3 })
        })
      });
    },
    minZoom: 10,
    maxZoom: 14
  });

  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'}) }),
      regionLayer, ringLayer, cityLayer
    ],
    view: new ol.View({
      center: ol.proj.fromLonLat([116.391, 39.907]),
      zoom: 12,
      minZoom: 4,
      maxZoom: 16
    }),
    controls: ol.control.defaults.defaults({ attribution: false })
  });

  var zoomEl = document.getElementById('zoom');

  function update() {
    var z = Number(zoomEl.value);
    map.getView().setZoom(z);
    document.getElementById('zoomVal').textContent = z;

    document.getElementById('tagCity').className =
      'tag' + (z >= 10 && z <= 14 ? ' on' : '');
    document.getElementById('tagRing').className =
      'tag' + (z >= 8 && z <= 12 ? ' on' : '');
    document.getElementById('tagRegion').className =
      'tag' + (z >= 4 && z <= 9 ? ' on' : '');
  }

  zoomEl.addEventListener('input', update);
  map.getView().on('change:resolution', function () {
    var z = Math.round(map.getView().getZoom());
    if (String(z) !== zoomEl.value) {
      zoomEl.value = z;
      document.getElementById('zoomVal').textContent = z;
    }
  });

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