Device Orientation

<!--
  说明：设备方向与地图旋转的中文示例，数据在页面内生成，可独立运行。
  核心逻辑：deviceorientation 事件 + view.setRotation(-alpha) + 权限申请
  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>设备方向与地图旋转</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;flex-wrap:wrap;font-size:12px;color:#58606e}
  .bar label{display:flex;gap:5px;align-items:center;cursor:pointer}
  .bar button{font:inherit;padding:3px 9px;border:1px solid #c9ced6;background:#fff;
       border-radius:5px;cursor:pointer;color:#333}
  .bar button:hover{background:#eef2f8}
  .bar input[type=range]{width:110px;vertical-align:middle}
  .bar input[type=text]{font:inherit;padding:2px 6px;border:1px solid #c9ced6;border-radius:4px}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3;position:relative}
  .panel{flex:0 0 auto;max-height:34%;overflow:auto;padding:8px 12px;font-size:12px;
       background:#fff;border-top:1px solid #e3e6ea;color:#3d4451}
  .panel pre{margin:0;font-family:Consolas,"Courier New",monospace;font-size:11px;
       white-space:pre-wrap;word-break:break-all;line-height:1.5}
  .ol-attribution{font-size:11px}

</style>
</head>
<body>
<div class="bar">
<button id="perm" type="button">请求传感器权限</button>
<label>方位角 <input type="range" id="alpha" min="0" max="360" value="0"></label>
<span id="info">—</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') {
    var errBox = document.getElementById('map');
    if (errBox) {
      errBox.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 view = new ol.View({
    center: fromLonLat([116.397, 39.909]),
    zoom: 12
  });

  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: view,
    controls: ol.control.defaults.defaults({attribution: false, zoom: true, rotate: true})
  });

  var info = document.getElementById('info');
  var slider = document.getElementById('alpha');
  var btn = document.getElementById('perm');

  function apply(deg) {
    view.setRotation(-deg * Math.PI / 180);
    info.textContent = '方位角 ' + deg.toFixed(1) + '° · 地图旋转 ' +
      (-deg).toFixed(1) + '° · 右上角按钮可复位正北';
  }

  function onOrient(evt) {
    if (evt.alpha === null || typeof evt.alpha === 'undefined') { return; }
    var deg = (360 - evt.alpha) % 360;
    slider.value = String(Math.round(deg));
    apply(deg);
  }

  slider.addEventListener('input', function () {
    apply(+this.value);
  });

  if (typeof DeviceOrientationEvent === 'undefined') {
    info.textContent = '当前环境不支持设备方向事件，请拖动滑块模拟';
    btn.disabled = true;
  } else if (typeof DeviceOrientationEvent.requestPermission === 'function') {
    info.textContent = '需要点击「请求传感器权限」，授权后自动跟随设备方向';
    btn.addEventListener('click', function () {
      DeviceOrientationEvent.requestPermission().then(function (state) {
        if (state === 'granted') {
          window.addEventListener('deviceorientation', onOrient);
          info.textContent = '已授权，正在监听设备方向';
        } else {
          info.textContent = '权限被拒绝，可拖动滑块模拟方位角';
        }
      }).catch(function () {
        info.textContent = '权限申请失败，可拖动滑块模拟方位角';
      });
    });
  } else {
    window.addEventListener('deviceorientation', onOrient);
    info.textContent = '已监听设备方向事件；桌面端无传感器时可拖动滑块';
  }

  apply(0);
})();
</script>
</body>
</html>