Epsg4326 View

<!--
  示例：EPSG:4326 视图
  要点：View 的 projection 设为 EPSG:4326，中心与要素直接写经纬度
  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>EPSG:4326 视图</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;font-size:12px;color:#58606e}
  .bar button{padding:4px 10px;border:1px solid #cfd4dc;border-radius:4px;
              background:#fff;cursor:pointer;font-size:12px}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <span id="center">—</span>
  <span id="equiv">—</span>
  <button id="toSh">跳转上海</button>
  <span>视图投影 EPSG:4326</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;
  }

  /* 视图用经纬度坐标系，要素也直接写经纬度 */
  var view = new ol.View({
    projection: 'EPSG:4326',
    center: [116.3974, 39.9093],
    zoom: 12
  });

  var features = [
    [116.3912, 39.9074, '天安门'],
    [116.4106, 39.9147, '王府井'],
    [116.3800, 39.9005, '西单'],
    [116.3966, 39.9182, '景山']
  ].map(function (p) {
    return new ol.Feature({
      geometry: new ol.geom.Point([p[0], p[1]]),
      name: p[2]
    });
  });

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

  layer.setStyle(function (feature) {
    return new ol.style.Style({
      image: new ol.style.Circle({
        radius: 6,
        fill: new ol.style.Fill({ color: '#c2410c' }),
        stroke: new ol.style.Stroke({ color: '#ffffff', width: 2 })
      }),
      text: new ol.style.Text({
        text: feature.get('name'),
        font: '500 11px sans-serif',
        offsetY: -13,
        fill: new ol.style.Fill({ color: '#16181d' }),
        stroke: new ol.style.Stroke({ color: '#ffffff', width: 3 })
      })
    });
  });

  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'}) }), layer],
    view: view,
    controls: ol.control.defaults.defaults({ attribution: false })
  });

  var centerOut = document.getElementById('center');

  function report() {
    var c = view.getCenter();
    centerOut.textContent = '中心 ' + c[0].toFixed(4) + ', ' + c[1].toFixed(4);
  }

  view.on('change:center', report);
  report();

  /* 对照：同一位置在 3857 与 4326 下的数值，用 fromLonLat / toLonLat 互转 */
  var merc = ol.proj.fromLonLat([116.3974, 39.9093]);
  var back = ol.proj.toLonLat(merc);
  document.getElementById('equiv').textContent =
    '对照 3857 ' + merc[0].toFixed(0) + ', ' + merc[1].toFixed(0) +
    ' ↔ 4326 ' + back[0].toFixed(4) + ', ' + back[1].toFixed(4);

  document.getElementById('toSh').addEventListener('click', function () {
    view.animate({ center: [121.4737, 31.2304], zoom: 11, duration: 900 });
  });

  /* 鼠标位置同样不需要投影转换 */
  map.on('pointermove', function (evt) {
    if (evt.dragging) {
      return;
    }
    var c = evt.coordinate;
    map.getTargetElement().title = c[0].toFixed(5) + ', ' + c[1].toFixed(5);
  });
})();
</script>
</body>
</html>