如何在 OpenLayers 的矢量图层上以编程方式选择特征？

Question

我目前正在寻找在 OpenLayers.Layer.Vector 中选择（或突出显示）矢量的解决方案。

我已经构建了一个简单的网格表，用户可以在其中选择一个向量（以 WKT 格式的字符串形式给出），该向量应该突出显示图层上的相应向量。用户访问网站时，gridtable 中的所有矢量都会绘制到地图上的矢量图层。

我发现我需要 OpenLayers.Control.ModifyFeature 的 selectFeature(feature) 函数或 OpenLayers.Control.SelectFeature（请参阅 dev.openlayers.org/apidocs/files/OpenLayers/Control/SelectFeature-js.html 的 select(功能）功能（可能不存在或不再存在？）。请参阅邮件列表中的帖子：osgeo-org.1803224.n2.nabble.com/Programatically-Select-a-Feature-tt2192485.html# a2193928 了解更多信息。

我尝试了以下但没有成功，所以我希望有人可以抓住这个代码行并可以向我展示一个工作代码 sn-p ;-)

// ... some initializing code
this.vlayer = new OpenLayers.Layer.Vector("VectorLayer");  // VectorLayer

// some controls
this.openLayerControlPoint = new OpenLayers.Control.DrawFeature(this.vlayer, OpenLayers.Handler.Point);
this.openLayerControlPolygon = new OpenLayers.Control.DrawFeature(this.vlayer, OpenLayers.Handler.Polygon);
this.openLayerControlModify = new OpenLayers.Control.ModifyFeature(this.vlayer, {
  mode: OpenLayers.Control.ModifyFeature.RESHAPE | OpenLayers.Control.ModifyFeature.DRAG,
  standalone: false
});

// just deactivate to make sure everything is really deactivated
this.openLayerControlPoint.deactivate();
this.openLayerControlPolygon.deactivate();
this.openLayerControlModify.deactivate();

// add the just created layer to the map
this.map.addLayer(this.vlayer);

// add all (deactivated) controls to the map
this.map.addControl(this.openLayerControlPoint);
this.map.addControl(this.openLayerControlPolygon);
this.map.addControl(this.openLayerControlModify);

后面的代码：

// ... another function doing the action
selectVector: function(wktVector) {
  this.openLayerControlModify.activate();

  // this is no elegant solution, this should only show how I would 
  // test the functionallity.
  for (var i = 0; i < this.vlayer.features.length; ++i) {
    // returns a WKT formatted string: 
    // 'POLYGON((xxxx.xxx xxxx.xxx), (xxxx.xxx xxxx.xxx))'
    var wktVectorCurrent = this.vlayer.features[i].geometry.toString(); 
    if (wktVector == wktVectorCurrent) {
      // \/ doesn't work :-(
      this.openLayerControlModify.selectFeature(this.vlayer.features[i]);
      break;
    }
  }
}

Answer 1

我不明白您为什么要使用 ModifyFeature 来选择功能。 OpenLayers.Control.SelectFeature 专门用于选择功能，因此我建议您改用此控件。

所以，创建 SelectFeature 控件：

var selectFeature = new OpenLayers.Control.SelectFeature(this.vlayer);
selectFeature.activate();

然后在你的 if 语句中（我猜它可以通过比较几何来找到你想要选择的特征？）使用 select 方法：

if (wktVector == wktVectorCurrent) {
   selectFeature.select(this.vlayer.features[i]);
}

根据文档，此方法应将功能标记为已选择并引发适当的事件：

 * Method: select
 * Add feature to the layer's selectedFeature array, render the feature as
 * selected, and call the onSelect function.

如果您想在选择要素时在地图上做某事（例如显示弹出窗口），您应该在创建矢量图层时订阅选择事件：

this.vlayer.events.on({'featureselected': function(){
   //Handle select event
}});