[OpenLayers-Users] Features Not Added to Vector Layer

[Phil Scadden]

I'm not convinced you have anything that would cause the 
beforefeatureadded to be triggered? I would have to say that while I 
dont know your application strategy, it seems counterintuitive to me. 
Maybe my way of doing lacks elegance, but here is my strategy for doing 
what I think you want to do:

1/ Create a general purpose vector layer.
selectedLayer = new OpenLayers.Layer.Vector("Selected Layer", {
     wrapDateLine: true,
     displayOutsideMaxExtent: true,
     displayInLayerSwitcher: false,
     attribution: "<a  href='http://www.gns.cri.nz' 
target='metadata'><img src='images/GNS_logo_mini.png'></a>"
});
map.addLayer(selectedLayer);

2/ Add in my other layers.

3/ create wfsprotocols for WFS query layers
                 lay.wfsProtocol = new OpenLayers.Protocol.WFS.v1_1_0({
                     url: spatialQueryNode.url,
                     featurePrefix: spatialQueryNode.featurePrefix,
                     featureType: spatialQueryNode.featureType,
                     srsName: "EPSG:900913"
                 });
4/ Now set up query strategies. To query by polygon, I do
             polySelCtrl = new 
OpenLayers.Control.DrawFeature(selectedLayer, OpenLayers.Handler.Polygon, {
                 geodesic: true,
                 handlerOptions: {
                     citeCompliant: false
                 }
             });
(the citecompliant stuff is about crossing 180 line). It draws onto the 
general purpose vector layer.
Actually do the query with this.
             polySelCtrl.events.register("featureadded", this, function 
(e) {
                 clearData(); // clean up popups etc, clear the 
selectLayer of features
wrapDateline(e.feature.geometry,map.baseLayer.maxExtent); // deals with 
dateline issues
                 var pfilter = new OpenLayers.Filter.Spatial({
                     type: OpenLayers.Filter.Spatial.INTERSECTS,
                     value: e.feature.geometry
                 });
                  map.div.style.cursor = 'wait';
                  loadingPanel.maximizeControl();

                 wfsProtocol.read({
                     filter:  pfilter,
                     propertyNames:propNames,
                     callback: processSpatialQuery,
                     scope: strategy
                 });
             });

processSpatialQuery deals with the returned values.
I do something very similar for mouse-click event creating a BBOX or 
DWithin filter
(            ptSelCtrl = new 
OpenLayers.Control.DrawFeature(selectedLayer, OpenLayers.Handler.Point,{
                 handlerOptions: {
                     citeCompliant: true
                 }
             });
) but you can use getFeature or similar instead.

If you want query based on filter of feature values, then you create the 
filter (eg
             var filter = new OpenLayers.Filter.Comparison({
                 type: OpenLayers.Filter.Comparison.LIKE,
                 matchCase:false,
                 property: fld.name,
                 value: "*" + searchText + "*"
             });
)
and action it with:
wfsProtocol.read({
        filter: new OpenLayers.Filter.Logical({
                 type: OpenLayers.Filter.Logical.OR,
                 filters: filter
         }),
         callback: processSpatialQuery,
         scope: strategy
      });
(Same callback!)

processSpatialQuery can be rather complex, but in skeleton:
     selectedLayer.destroyFeatures();
     map.div.style.cursor = 'default';
     loadingPanel.minimizeControl();
    ....
and
   selectedLayer.addFeatures(request.features)

In summary have a general purpose selectedLayer for drawing and 
highlighting; centralised request handlers (processSpatialQuery) used 
for point, polygon and text queries, and used the wfsprotocol handler 
throughout.

Not shown, but I actually add the wfsprotocol and point/poly controls to 
the layer object.

I hope that might help.


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