Question

我有一个OpenLayers 4地图，它具有单击交互作用，并且具有用于“ select”事件的相应事件处理程序，该事件处理程序会更改所选要素样式。

let clickInteraction = new olInteractionSelect({
  layers: function (layer: any) {
    return layer.get('selectable') == true;
  },
  condition: olEventCondition.singleClick,
  filter: (feature: any, layer: any) => {

    let shouldReturn: boolean = false;

    switch (layer.get(this.LAYER_PROPERTY_ID)) {
      case this.LAYER_ID_POINTS:
        this.onPointClick(feature.getId());
        shouldReturn = true;
        break;
      case this.LAYER_ID_AREAS:
        this.onAreaClick(feature.getId());
        shouldReturn = true;
        break;
      default:
        break;
    }
    return shouldReturn;
  }
});

let __this = this;

clickInteraction.on('select', function (evt: any) {
  let selected = evt.selected;
  let deselected = evt.deselected;

  //Select and set style for newly selected features
  if (selected.length) {
    selected.forEach(function (feature: any) {
      if (feature.get(__this.FEATUREKEY_SELECTEDSTYLEID)) {
        feature.setStyle(__this.createStyleFnFeatureSelected(feature.get(__this.FEATUREKEY_SELECTEDSTYLEID)));
      }
    });
  } else {
    deselected.forEach(function (feature: any) {
      if (feature.get(__this.FEATUREKEY_STYLEID)) {
        feature.setStyle(__this.createStyleFn(feature.get(__this.FEATUREKEY_STYLEID)));
      }
    });
  }
});

this.map.addInteraction(clickInteraction);

每次选择一个新功能时，我都要设置所有先前选择的功能的样式。我不知道是什么时候调用了单击交互的“选择”事件，如何在地图层上获取所有先前选择的要素的集合？

地图上有数千个要素，因此从性能角度来看，对所有要素进行迭代是不可行的。我要实现的只是获取以前选择的功能，而不是当前单击交互事件中选择或取消选择的功能。

Answer 1

您可以简单地维护所选要素的队列，并在选择新要素时将其添加到队列中。队列的处理可以是可选的，但必须在添加新功能之前完成

let prevSelection = [];

clickInteraction.on('select', function (evt: any) {
  let selected = evt.selected;
  let deselected = evt.deselected;

  //Restyle previously selected features now if desired (or leave until next time)
  if (myCondition) {
    prevSelection.forEach(
      ...
    )
    prevSelection = [];
  }

  //Append newly selected features to queue for next time 
  prevSelection = prevSelection.concat(selected);

  //Select and set style for newly selected features
  if (selected.length) {

如何在OpenLayers地图图层中获取所有先前选择的要素？

1 个答案: