Select Features

 0 selected features

Example of using the Select interaction.

Choose between Single-click, Click, Hover and Alt+Click as the event type for selection in the combobox below. When using Single-click or Click you can hold do Shift key to toggle the feature in the selection.

Note: when Single-click is used double-clicks won't select features. This in contrast to Click, where a double-click will both select the feature and zoom the map (because of the DoubleClickZoom interaction). Note that Single-click is less responsive than Click because of the delay it uses to detect double-clicks.

In this example, a listener is registered for the Select interaction's select event in order to update the selection status above.

<!DOCTYPE html>
<html>
  <head>
    <title>Select Features</title>
    <link rel="stylesheet" href="https://openlayers.org/en/v3.20.0/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/v3.20.0/build/ol.js"></script>
  </head>
  <body>
    <div id="map" class="map"></div>
    <form class="form-inline">
      <label>Action type &nbsp;</label>
        <select id="type" class="form-control">
          <option value="click" selected>Click</option>
          <option value="singleclick">Single-click</option>
          <option value="pointermove">Hover</option>
          <option value="altclick">Alt+Click</option>
          <option value="none">None</option>
        </select>
      <span id="status">&nbsp;0 selected features</span>
      <br />
      <label>Hit tolerance for selecting features </label>
        <select id="hitTolerance" class="form-control">
          <option value="0" selected>0 Pixels</option>
          <option value="5">5 Pixels</option>
          <option value="10">10 Pixels</option>
        </select>
        <canvas id="circle" style="vertical-align: middle"/>
    </form>
    <script>
      var raster = new ol.layer.Tile({
        source: new ol.source.OSM()
      });

      var vector = new ol.layer.Vector({
        source: new ol.source.Vector({
          url: 'https://openlayers.org/en/v3.20.0/examples/data/geojson/countries.geojson',
          format: new ol.format.GeoJSON()
        })
      });

      var map = new ol.Map({
        layers: [raster, vector],
        target: 'map',
        view: new ol.View({
          center: [0, 0],
          zoom: 2
        })
      });

      var select = null;  // ref to currently selected interaction

      // select interaction working on "singleclick"
      var selectSingleClick = new ol.interaction.Select({
        multi: true // multi is used in this example if hitTolerance > 0
      });

      // select interaction working on "click"
      var selectClick = new ol.interaction.Select({
        condition: ol.events.condition.click,
        multi: true
      });

      // select interaction working on "pointermove"
      var selectPointerMove = new ol.interaction.Select({
        condition: ol.events.condition.pointerMove,
        multi: true
      });

      var selectAltClick = new ol.interaction.Select({
        condition: function(mapBrowserEvent) {
          return ol.events.condition.click(mapBrowserEvent) &&
              ol.events.condition.altKeyOnly(mapBrowserEvent);
        },
        multi: true
      });

      var selectElement = document.getElementById('type');

      var changeInteraction = function() {
        if (select !== null) {
          map.removeInteraction(select);
        }
        var value = selectElement.value;
        if (value == 'singleclick') {
          select = selectSingleClick;
        } else if (value == 'click') {
          select = selectClick;
        } else if (value == 'pointermove') {
          select = selectPointerMove;
        } else if (value == 'altclick') {
          select = selectAltClick;
        } else {
          select = null;
        }
        if (select !== null) {
          map.addInteraction(select);
          select.on('select', function(e) {
            document.getElementById('status').innerHTML = '&nbsp;' +
                e.target.getFeatures().getLength() +
                ' selected features (last operation selected ' + e.selected.length +
                ' and deselected ' + e.deselected.length + ' features)';
          });
        }
      };


      /**
       * onchange callback on the select element.
       */
      selectElement.onchange = changeInteraction;
      changeInteraction();

      var selectHitToleranceElement = document.getElementById('hitTolerance');
      var circleCanvas = document.getElementById('circle');

      var changeHitTolerance = function() {
        var value = parseInt(selectHitToleranceElement.value, 10);
        selectSingleClick.setHitTolerance(value);
        selectClick.setHitTolerance(value);
        selectPointerMove.setHitTolerance(value);
        selectAltClick.setHitTolerance(value);

        var size = 2 * value + 2;
        circleCanvas.width = size;
        circleCanvas.height = size;
        var ctx = circleCanvas.getContext('2d');
        ctx.clearRect(0, 0, size, size);
        ctx.beginPath();
        ctx.arc(value + 1, value + 1, value + 0.5, 0, 2 * Math.PI);
        ctx.fill();
        ctx.stroke();
      };

      selectHitToleranceElement.onchange = changeHitTolerance;
      changeHitTolerance();
    </script>
  </body>
</html>