Re: [Gwt-openlayers-users] Cluster Strategy

[Weber, S. H. <ste...@si...>]

OK, I found the solution. 

2 Problems 

1: Cluster strategy activation does nothing clustering only happens when you add features _after_ the control is
activated. (from http://osgeo-org.1803224.n2.nabble.com/Cluster-strategy-activation-td5078623.html)

2: the VectorFeatures have to be added as an array (not separately)

So here is the running code:

-------------------------------------------
package com.siemens.test.client;

import org.gwtopenmaps.openlayers.client.LonLat;
import org.gwtopenmaps.openlayers.client.Map;
import org.gwtopenmaps.openlayers.client.MapOptions;
import org.gwtopenmaps.openlayers.client.MapWidget;
import org.gwtopenmaps.openlayers.client.Style;
import org.gwtopenmaps.openlayers.client.control.LayerSwitcher;
import org.gwtopenmaps.openlayers.client.control.MousePosition;
import org.gwtopenmaps.openlayers.client.control.NavToolbar;
import org.gwtopenmaps.openlayers.client.control.PanZoomBar;
import org.gwtopenmaps.openlayers.client.control.Scale;
import org.gwtopenmaps.openlayers.client.feature.VectorFeature;
import org.gwtopenmaps.openlayers.client.geometry.Point;
import org.gwtopenmaps.openlayers.client.layer.Layer;
import org.gwtopenmaps.openlayers.client.layer.OSM;
import org.gwtopenmaps.openlayers.client.layer.Vector;
import org.gwtopenmaps.openlayers.client.layer.VectorOptions;
import org.gwtopenmaps.openlayers.client.strategy.Strategy;
import org.gwtopenmaps.openlayers.client.util.JSObject;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.user.client.Random;
import com.google.gwt.user.client.ui.RootPanel;

/**
 * Entry point classes define <code>onModuleLoad()</code>.
 */
public class ClusterStrategy implements EntryPoint {

	private Map map;
	private Vector vectorLayer;
	private OSM osmLayer;
	private LonLat centerOfGermany = new LonLat(9.77, 51.16);

	/**
	 * This is the entry point method.
	 */
	public void onModuleLoad() {
		MapOptions config = new MapOptions();
		config.setNumZoomLevels(32);
		config.setProjection("EPSG:4326");
		MapWidget mapWidget = new MapWidget("900px", "500px", config);
		map = mapWidget.getMap();
		map.addControl(new PanZoomBar());
		map.addControl(new NavToolbar());
		map.addControl(new MousePosition());
		map.addControl(new LayerSwitcher());
		map.addControl(new Scale());
		centerOfGermany.transform("EPSG:4326", "EPSG:900913");
		osmLayer = OSM.Mapnik("OpenStreetMap");
		vectorLayer = createLayer();
		map.addLayers(new Layer[] { osmLayer, vectorLayer });
		map.setCenter(centerOfGermany, 5);
		RootPanel.get("main").add(mapWidget);
		// Problem 1: add points after control is activated
		addSomePoints(vectorLayer);

	}

	private Vector createLayer() {
		// Create the vectorOptions
		VectorOptions vectorOptions = new VectorOptions();
		vectorOptions.setStyle(createStyle());
		Strategy st = new Strategy(createClusterStrategy()) {
		};
		vectorOptions.setStrategies(new Strategy[] { st });
		Vector layer = new Vector("Vector Layer", vectorOptions);
		return layer;
	}

	/**
	 * @param layer
	 */
	private void addSomePoints(Vector layer) {
		// Problem 2: add points as array together
		VectorFeature[] features = new VectorFeature[500];
		for (int i = 0; i < 500; i++) {
			double lon = 9 + Random.nextDouble()*5;
			double lat = 45 + Random.nextDouble()*5;
			LonLat lonlat = new LonLat(lon, lat);
			lonlat.transform("EPSG:4326", "EPSG:900913");
			Point point = new Point(lonlat.lon(), lonlat.lat());
			VectorFeature pointFeature = new VectorFeature(point);
			features[i] = pointFeature;
		}
		layer.addFeatures(features);
	}

	private Style createStyle() {
		Style style = new Style();
		style.setStrokeColor("#000000");
		style.setStrokeWidth(1);
		style.setFillColor("#FF0000");
		style.setFillOpacity(0.5);
		style.setPointRadius(10);
		style.setStrokeOpacity(1.0);
		return style;
	}

	private static native JSObject createClusterStrategy() /*-{
		var clusterStrategy = new $wnd.OpenLayers.Strategy.Cluster({
			distance : 20,
			threshold : 1
		});
		return clusterStrategy;
	}-*/;

}
-------------------------------------------

Stefan

-----Ursprüngliche Nachricht-----
Von: Alexander Solovets [mailto:aso...@gm...] 
Gesendet: Donnerstag, 19. Mai 2011 13:50
An: Weber, Stefan Hagen
Cc: gwt...@li...
Betreff: Re: [Gwt-openlayers-users] Cluster Strategy

Hello, Stefan!

See JSNI explanation on GWT project page. Or you could just look at
OL-GWT sources and do it similarly.