[GIS] Select features of layer which is not on top in OpenLayers

geoserveropenlayers-2wfs

I have posted this question before on the general StackOverflow forum:
https://stackoverflow.com/questions/16278569/select-features-of-layer-which-is-not-on-top

In short my problem is that I have a baselayer, an overlay layer and a WFS layer in OL.
The base and overlay layers are WMS using GWC in GeoServer.
I want to select a feature of the WFS layer but KEEP the overlay layer on top.

By binding a selectFeature control to the WFS layer moves the layer on top.
Using

map.setLayerZIndex(overlayLayer, map.Z_INDEX_BASE["Feature"]+10);

I move the overlay layer back.
But now I can no longer select a feature of the WFS layer.

Adding the overlayLayer to the SelectFeature control doesn't work because it is a WMS layer.

How can I select a feature on the WFS layer which is not on top?
I've tried the GetFeature control, but that requires a roundtrip to the server and I don't want.

I've made an sample of my problem at http://www.smartdakscan.nl/webapps/assen/selectFeature.html

Any help is much appreciated.

Best Answer

Use setLayerIndex instead setLayerZIndex which is a "private" method. Using the setLayerZIndex you simple change the z-index of the DOM elements but not the position of the layer within the map's layer stack.

Once you have ordered the layers as you want, you are right using the SelectFeature control passing the desired layer (WFS) where to select features.

Cheers.

Related Solutions

[GIS] WFS GetFeature control doesn’t take ‘viewparams’ into account

Looking at the source of the WFS.fromWMSLayer function, it looks like you should pass in your viewparams as an additional option:

        protocol: OpenLayers.Protocol.WFS.fromWMSLayer(test, 
                                                       {viewparams: 'x:'+myX+';y:'+myY}),

Check the URL that is called when you select a feature - and hopefully the viewparams will be added to the URL.

If you wanted to apply a filter to a WFS layer you can play around with the filter code and the XML it generates on this demo.

Once you have the filter code correct then set the WFS layer's filter filter property.

        wfsLayer.filter = my_filter;

As you don't have a WFS layer you could try the following - the parameters may be copied across - you'd have to test.

        protocol: OpenLayers.Protocol.WFS.fromWMSLayer(test, 
                                                       {filter: my_filter}),

[GIS] Select single feature from multiple types with WFS in OpenLayers

If your WFS supports it (and it looks like you're using GeoServer, which does), OpenLayers can query multiple feature types in a single WFS query:

var featureTypes = ["parcelshape_lin", "wmain_lin", "buildings_pol"];

var allLayersControl = new OpenLayers.Control.GetFeature({
    protocol: OpenLayers.Protocol.WFS.fromWMSLayer(wms, {
        url: baseUrl + "/geoserver/wfs",
        featureType: featureTypes
    }),
    hover: false
});

This is exactly what I do in my OpenLayers/GeoServer installation, the only difference being that I create a new OpenLayers.Protocol.WFS({ ... }) manually instead of using fromWMSLayer. However, it should work identically.

Just register the events on allLayerscontrol and the GetFeature control will take care of parsing the geometries and finding the best match. If you're interested in how it does that, I'd recommend taking a look at the source for the control (GetFeature.js in OpenLayers).

Best Answer

Related Solutions

[GIS] WFS GetFeature control doesn’t take ‘viewparams’ into account

[GIS] Select single feature from multiple types with WFS in OpenLayers

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