Device Orientation——设备方向

最新推荐文章于 2024-11-08 15:33:24 发布

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最新推荐文章于 2024-11-08 15:33:24 发布

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该示例详细解释了如何监测和响应设备方向的变化，主要关注于移动设备上的设备方向API使用。

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This example shows how to track changes in device orientation.

这个例子用来展示如何去追踪设备方向的改变。

代码：

<!DOCTYPE html>
<html>
  <head>
    <title>Device Orientation</title>
    <link rel="stylesheet" href="https://openlayers.org/en/v4.2.0/css/ol.css" type="text/css">
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>
    <script src="https://openlayers.org/en/v4.2.0/build/ol.js"></script>
  </head>
  <body>
    <div id="map" class="map"></div>
    <label>
      track changes
      <input id="track" type="checkbox"/>
    </label>
    <p>
      α : <code id="alpha"></code>  
      β : <code id="beta"></code>  
      γ : <code id="gamma"></code>  
      heading : <code id="heading"></code>
    </p>
    <script>
      var projection = ol.proj.get('EPSG:3857');
      var view = new ol.View({
        center: [0, 0],
        projection: projection,
        extent: projection.getExtent(),
        zoom: 2
      });
      var map = new ol.Map({
        layers: [
          new ol.layer.Tile({
            source: new ol.source.OSM()
          })
        ],
        target: 'map',
        controls: ol.control.defaults({
          attributionOptions: /** @type {olx.control.AttributionOptions} */ ({
            collapsible: false
          })
        }),
        view: view
      });

      // 创建一个DeviceOrientation对象
      var deviceOrientation = new ol.DeviceOrientation();

      function el(id) {
        return document.getElementById(id);
      }

      // 根据track change复选框的选中状态决定是否进行跟踪
      el('track').addEventListener('change', function() {
        deviceOrientation.setTracking(this.checked);
      });

      // 当设备的方向改变时更新alpha、beta、gamma和heading的值
      deviceOrientation.on('change', function() {
        el('alpha').innerText = deviceOrientation.getAlpha() + ' [rad]';
        el('beta').innerText = deviceOrientation.getBeta() + ' [rad]';
        el('gamma').innerText = deviceOrientation.getGamma() + ' [rad]';
        el('heading').innerText = deviceOrientation.getHeading() + ' [rad]';
      });

      // 倾斜地图
      deviceOrientation.on(['change:beta', 'change:gamma'], function(event) {
        var center = view.getCenter();
        var resolution = view.getResolution();
        var beta = event.target.getBeta() || 0;
        var gamma = event.target.getGamma() || 0;

        center[0] -= resolution * gamma * 25;
        center[1] += resolution * beta * 25;

        view.setCenter(view.constrainCenter(center));
      });
    </script>
  </body>
</html>