使多个矢量层可在OpenLayers中单击

Question

我正在开发一个OpenLayers映射，它将同时显示多个KML层。我希望能够点击任何层的功能，并有一个弹出窗口向我显示一些信息。到目前为止，我只能点击最近添加的图层。如果我想点击之前添加的层，我必须关闭之前添加的所有层。显然，这并不理想。到目前为止，这是我的代码：

var select = [];
function addLayer(layerId, layerLink, layerColor)
{
    var kmlLayer = new OpenLayers.Layer.Vector("Layer_"+layerId, {
        strategies: [new OpenLayers.Strategy.Fixed()],
        protocol: new OpenLayers.Protocol.HTTP({
            url: layerLink,
            format: new OpenLayers.Format.KML({
        extractStyles: true, 
        extractAttributes: true,
        maxDepth: 2
        })
    })
    });
    kmlLayer.events.on({
        "featureselected": onKMLSelect,
        "featureunselected": onKMLUnselect
    });
    select["Layer_"+layerId] = new OpenLayers.Control.SelectFeature(kmlLayer);
    map.addControl(select["Layer_"+layerId]);
    select["Layer_"+layerId].activate();  
    map.addLayer(kmlLayer);
}
function onKMLPopupClose(evt) {
    for(s in select)
    {
        select[s].unselectAll();
    }
}
function onKMLSelect(event) {
        var feature = event.feature;
    var content = "<h2>"+feature.attributes.name + "</h2>" + feature.attributes.description;
    popup = new OpenLayers.Popup.FramedCloud("chicken", 
                             feature.geometry.getBounds().getCenterLonLat(),
                             new OpenLayers.Size(100,100),
                             content,
                             null, true, onKMLPopupClose);
    feature.popup = popup;
    map.addPopup(popup);
}
function onKMLUnselect(event) {
    var feature = event.feature;
    if(feature.popup) {
        map.removePopup(feature.popup);
        feature.popup.destroy();
        delete feature.popup;
    }
}

如有任何帮助，我们将不胜感激。谢谢，

Answer 1

我不久前也遇到了同样的问题。你可以从Openlayers中找到关于这一点的好例子示例：Openlayers在多层上选择功能示例。

以下是代码的主要部分：

var map, selectControl;
function init(){
    map = new OpenLayers.Map('map');
    var wmsLayer = new OpenLayers.Layer.WMS(
        "OpenLayers WMS", 
        "http://vmap0.tiles.osgeo.org/wms/vmap0",
        {layers: 'basic'}
    ); 
    var vectors1 = new OpenLayers.Layer.Vector("Vector Layer 1");
    var vectors2 = new OpenLayers.Layer.Vector("Vector Layer 2");
    map.addLayers([wmsLayer, vectors1, vectors2]);
    map.addControl(new OpenLayers.Control.LayerSwitcher());
    selectControl = new OpenLayers.Control.SelectFeature(
        [vectors1, vectors2]
    );
    map.addControl(selectControl);
    selectControl.activate();
    map.setCenter(new OpenLayers.LonLat(0, 0), 3);
    vectors1.addFeatures(createFeatures());
    vectors2.addFeatures(createFeatures());

    vectors1.events.on({
        "featureselected": function(e) {
            showStatus("selected feature "+e.feature.id+" on Vector Layer 1");
        },
        "featureunselected": function(e) {
            showStatus("unselected feature "+e.feature.id+" on Vector Layer 1");
        }
    });
    vectors2.events.on({
        "featureselected": function(e) {
            showStatus("selected feature "+e.feature.id+" on Vector Layer 2");
        },
        "featureunselected": function(e) {
            showStatus("unselected feature "+e.feature.id+" on Vector Layer 2");
        }
    });
}

Answer 2

这就是我所做的，让CHOSEN层上的所有功能都可以选择调用弹出窗口：

var selectStop = new OpenLayers.Control.SelectFeature([layerKMLClient, layerKMLStops,  layerKMLTarget],{onSelect: onFeatureSelect, onUnselect: onFeatureUnselect});
    layerKMLStops.events.on({
                "featureselected": onFeatureSelect,
                "featureunselected": onFeatureUnselect
            });
    layerKMLClient.events.on({
                "featureselected": onFeatureSelect,
                "featureunselected": onFeatureUnselect
            });
    layerKMLTarget.events.on({
                "featureselected": onFeatureSelect,
                "featureunselected": onFeatureUnselect
            });
    map.addControl(selectStop);
    selectStop.activate(); 

注意，我有多个其他层（主要来自KML文件，但也有一些来自txt文件的矢量层），它们的功能是不可选择的。可以通过为每个图层类型自定义onFeatureSelect来更改行为。

好处：如果你决定在（某些）层上使用cluster strategy（相信我，在某个时间点你会的）-在你的onFeatureSelected函数语句中检查feature.cluster是否为true：

function onFeatureSelect(event) {
   var feature = event.feature;
   if (feature.cluster) {