javascript - beforefeatureadded 事件等效于 OpenLayers 3

Question

对于 openlayers 2，您有一个名为 beforefeatureadded 的事件，您可以在实际添加新功能之前进行验证。什么是 OpenLayers 3 的 beforefeatureadded 事件？

OpenLayers 2 示例:

layer.events.register("beforefeatureadded", layer, validationFunction);

Answer 1

与 OpenLayers 2 beforefeatureadded 事件等效的是为绘制的要素使用暂存集合:

var source = new ol.source.Vector();
var features = new ol.Collection();
features.on('add', function(evt) {
  var feature = evt.element;
  if (conditionMet(feature)) {
    source.addFeature(evt.element);
  }
  // clear the staging collection
  features.pop();
});

也可以使用 Draw 条件，这正是 @robert-smith 在这里真正想要的:

var draw = new ol.interaction.Draw({
  condition: function(evt) {
    return ol.events.condition.noModifierKeys(evt) && conditionMet(evt);
  }
});