GWT OpenLayers set sum of values of underlying VectorFeatures on cluster point

Question

I'm using gwt-openlayers-1.0, currently learning this example (Animated Cluster Strategy).

In my project each VectoreFeature has a numeric label and I want to display sums of label values of underlying points on each cluster point. Is there a way to do that?

upd:
According to this article (The “Most Important” Strategy part) in JS it would look like this:

// for each feature:
feature.attributes = { result_count: 10 };
...
var style = new OpenLayers.Style({
  ...
  } , context: {
    label: function(feature) {
      if (feature.cluster) {
        var result_count = 0;
        for (var i = 0; i < feature.cluster.length; i++) {
          result_count += feature.cluster[i].attributes.result_count;
        }
        features.attributes.label = result_count.toString();
      } else {
        features.attributes.label = features.attributes.result_count.toString();
      }
    }
  }

But I can't find a way to implement this in gwt-openlayers:

org.gwtopenmaps.openlayers.client.Style style = new org.gwtopenmaps.openlayers.client.Style();
style.setLabel( ??? );

score 1 · Answer 1 · answered Feb 10 '14 at 13:15

1

I don't think this is possible. I also don't think this is possible in standard OpenLayers with the standard AnimatedCluster.

Your best guess is to first go to https://github.com/acanimal/AnimatedCluster and ask there if what you want is possible (in standard openlayers).

If they say it is possible, and say how come back here and I can look further into it. If they say it is also not possible in standard openlayers, then it is also not possible in gwt openlayers.

answered Feb 10 '14 at 13:15

Knarf

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It's possible in JS according to this article: http://openflights.org/blog/2009/10/21/customized-openlayers-cluster-strategies/ (look at "The most important strategy" section). If only I knew how to attach function the same way in gwt-openlayers. – Moonsera Feb 10 '14 at 14:10
I believe the example you provide uses the standaard clustering in OpenLayers. You are trying to use Animated Cluster which is a 3rd party addon with different posibilities. This is a GWT-Openlayers example with the default cluster strategy : http://demo.gwt-openlayers.org/gwt_ol_showcase/GwtOpenLayersShowcase.html?example=Cluster%20Strategy%20Threshold Looking a bit further. That animated cluster extends the normal cluster in JS. So probably everything possible in normal cluster is possible in animated. IF I have time I will look into it. Maybe for now try with normal Cluster strategy. – Knarf Feb 11 '14 at 07:46
I already switched to standard clustering, and for example I provided it doesn't matter which strategy is used. – Moonsera Feb 11 '14 at 07:49
I'll look into it when I have some time. – Knarf Feb 11 '14 at 07:55
Thanks, will be much appreciated. Now I'm searching how to implement inline JS functions in GWT. – Moonsera Feb 11 '14 at 08:07

score 1 · Answer 2 · answered Feb 11 '14 at 10:13

I enhanced the Animated Cluster With Popup example to do what you ask. Will take some time before this is online though.

Changes I made are :

First I added an attribute to each feature added to the map. This feature just is a random number that we want to display the sum of when clicking a clustered feature :

for (int i = 0; i < points.size(); i++)
{
   features[i] = new VectorFeature(points.get(i));
   Attributes attributes = new Attributes();
   attributes.setAttribute("examplenumber", Random.nextInt(10));
   features[i].setAttributes(attributes);
}

Second change is in the public void onFeatureSelected(FeatureSelectedEvent eventObject)

int totalNumber = 0;
VectorFeature[] clusters = eventObject.getVectorFeature().getCluster();
for (int i = 0; i < clusters.length; i++)
{
   GWT.log("examplenumber = " + clusters[i].getAttributes().getAttributeAsInt("examplenumber"));
   totalNumber += clusters[i].getAttributes().getAttributeAsInt("examplenumber");
}

Now totalnumber contains the sum of all examplenumber attribute values.

I believe this solves your problem ?

And showcase is now also updated : http://demo.gwt-openlayers.org/gwt_ol_showcase/GwtOpenLayersShowcase.html?example=Animated%20cluster%20with%20popup — Knarf, Feb 11 '14 at 10:17

score 0 · Accepted Answer · answered Feb 11 '14 at 11:34

In method where I assign strategy to the VectorLayer:

{
    org.gwtopenmaps.openlayers.client.Style style = new org.gwtopenmaps.openlayers.client.Style();
    style.setJSObject(getOpenLayersStyle());
}

And where the magic is done:

private native JSObject getOpenLayersStyle() /*-{
    var style = new $wnd.OpenLayers.Style({
        fontColor: "#FFFFFF",
        fontSize: "12px",
        label: "${countLabel}"
        }, { context: {
            countLabel: function(feature) {
                var countLabel;
                if (feature.cluster) {
                    var result_count = 0;
                    for (var i = 0; i < feature.cluster.length; i++) {
                        result_count += feature.cluster[i].attributes.result_count;
                    }
                    countLabel = result_count.toString();
                } else {
                    countLabel = feature.attributes.result_count.toString();
                }
                feature.attributes.label = countLabel;
                return countLabel;
            }
        }
    });
    return style;
}-*/;

Using native methods is always a possible solution. But the goal of gwt-openlayers is that you don't need to use native methods. Anyway, good to see that the problem is solved :) — Knarf, Feb 11 '14 at 12:12

GWT OpenLayers set sum of values of underlying VectorFeatures on cluster point

3 Answers3