Box Selection——盒形方式选择

来源：互联网发布：角色数据库设计编辑：程序博客网时间：2024/06/06 01:21

This example shows how to use a DragBox interaction to select features. Selected features are added to the feature overlay of a select interaction (ol.interaction.Select) for highlighting.

Use Ctrl+Drag (Command+Drag on Mac) to draw boxes.

这个例子用来展示如何使用DragBox交互控件来选择要素，选中的要素被添加到选择交互控件(ol.interaction.Select)
的要素叠加层中来进行高亮显示。

使用Ctrl+Drag (Mac系统使用Command+Drag)来绘制盒形。

代码：

<!DOCTYPE html><html>  <head>    <title>Box Selection</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>    <style>      .ol-dragbox {        background-color: rgba(255,255,255,0.4);        border-color: rgba(100,150,0,1);      }    </style>  </head>  <body>    <div id="map" class="map"></div>    <div id="info">No countries selected</div>    <script>      //加载GeoJson格式的矢量数据     var vectorSource = new ol.source.Vector({        url: 'https://openlayers.org/en/v4.2.0/examples/data/geojson/countries.geojson',        format: new ol.format.GeoJSON()      });      var map = new ol.Map({        layers: [          new ol.layer.Tile({            source: new ol.source.OSM()          }),          new ol.layer.Vector({            source: vectorSource          })        ],        target: 'map',        view: new ol.View({          center: [0, 0],          zoom: 2        })      });      //创建选择交互控件      var select = new ol.interaction.Select();      map.addInteraction(select);      //获取所有选择的要素      var selectedFeatures = select.getFeatures();      //创建DragBox交互控件      var dragBox = new ol.interaction.DragBox({         //ol.events.condition.platformModifierKeyOnly         //Return true if only the platform-modifier-key (the meta-key on Mac, ctrl-key otherwise) is pressed,         //如果只按下platform-modifier-key（Mac平台是meta-key，其他平台是ctrl-key）则返回true         //false otherwise         //其他都返回false        condition: ol.events.condition.platformModifierKeyOnly      });      map.addInteraction(dragBox);      dragBox.on('boxend', function() {        //获取当前绘制的范围        var extent = dragBox.getGeometry().getExtent();        //遍历当前范围内的每一个要素，并把它添加到selectedFeatures集合中       vectorSource.forEachFeatureIntersectingExtent(extent, function(feature) {          selectedFeatures.push(feature);        });      });      //每次绘制之前清除selectedFeatures中的所有要素      dragBox.on('boxstart', function() {        selectedFeatures.clear();      });      var infoBox = document.getElementById('info');       selectedFeatures.on(['add', 'remove'], function() {        //遍历selectedFeatures中的每一个要素，并返回每一个要素的名称       var names = selectedFeatures.getArray().map(function(feature) {          return feature.get('name');        });        //如果names数组的长度大于0，则把它用逗号分隔添加到id为info的DIV标签中       if (names.length > 0) {          infoBox.innerHTML = names.join(', ');        } else {          infoBox.innerHTML = 'No countries selected';        }      });    </script>  </body></html>

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