Rotation

<!--
  示例：旋转地图
  要点：View.setRotation 使用弧度，滑块与按钮联动并回显角度
  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>旋转地图</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:12px;align-items:center;font-size:12px;color:#58606e;flex-wrap:wrap}
  .bar input[type=range]{width:180px}
  .bar button{font:inherit;font-size:12px;padding:4px 9px;border:1px solid #ccd1d9;
       border-radius:4px;background:#fff;color:#16181d;cursor:pointer}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <button data-angle="0">0°</button>
  <button data-angle="90">90°</button>
  <button data-angle="180">180°</button>
  <button data-angle="270">270°</button>
  <label>角度 <input type="range" id="angle" min="-180" max="180" value="0"></label>
  <span>当前 <b id="val">0°</b></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 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'}) })
    ],
    view: new ol.View({
      center: fromLonLat([116.391263, 39.907359]),
      zoom: 12,
      rotation: 0
    }),
    controls: ol.control.defaults.defaults({
      attribution: false,
      rotate: false
    })
  });

  var view = map.getView();
  var slider = document.getElementById('angle');
  var valEl = document.getElementById('val');

  function applyDegrees(deg) {
    /* 旋转以弧度为单位，顺时针为正，和 CSS rotate 的方向一致 */
    view.setRotation(deg * Math.PI / 180);
  }

  function sync(deg) {
    var normalized = ((deg + 180) % 360 + 360) % 360 - 180;
    slider.value = normalized;
    valEl.textContent = Math.round(normalized) + '°';
  }

  slider.addEventListener('input', function () {
    applyDegrees(Number(this.value));
    valEl.textContent = this.value + '°';
  });

  Array.prototype.forEach.call(
    document.querySelectorAll('.bar button[data-angle]'),
    function (btn) {
      btn.addEventListener('click', function () {
        var deg = Number(btn.getAttribute('data-angle'));
        sync(deg);
        applyDegrees(deg);
      });
    }
  );

  /* 用户用默认交互（Alt + 拖动）旋转时，回写滑块 */
  view.on('change:rotation', function () {
    sync(view.getRotation() * 180 / Math.PI);
  });
})();
</script>
</body>
</html>