Imreking Imreking - 3 months ago 22
Java Question

Display WMS layer in GWT-Openlayers

I use GWT-Openlayers and i want to add a WMS layer to my Map. Here is the code:

...
MapOptions defaultMapOptions = new MapOptions();
defaultMapOptions.setNumZoomLevels(7);

//Create a MapWidget
MapWidget mapWidget = new MapWidget("700px", "700px", defaultMapOptions);

GoogleV3Options gSatelliteOptions = new GoogleV3Options();
gSatelliteOptions.setIsBaseLayer(true);
gSatelliteOptions.setType(GoogleV3MapType.G_SATELLITE_MAP);
GoogleV3 gSatellite = new GoogleV3("Google Satellite", gSatelliteOptions);

mapWidget.getMap().addLayer(gSatellite);

//Create a WMS layer as base layer
WMSParams wmsParams = new WMSParams();
wmsParams.setFormat("image/png");
wmsParams.setLayers("topp:tasmania_state_boundaries");
wmsParams.setStyles("");
wmsParams.setParameter("transparent", "true");

//create a WMS layer
WMSOptions wmsLayerParams = new WMSOptions();
wmsLayerParams.setUntiled();
wmsLayerParams.setTransitionEffect(TransitionEffect.RESIZE);
wmsLayerParams.setIsBaseLayer(false);

String wmsUrl = "http://demo.opengeo.org/geoserver/wms";

final WMS wmsLayer = new WMS("Basic WMS", wmsUrl, wmsParams,
wmsLayerParams);

//Add the WMS to the map
Map map = mapWidget.getMap();
map.addLayer(wmsLayer);

//Lets add some default controls to the map
map.addControl(new LayerSwitcher()); //+ sign in the upperright corner to display the layer switcher
map.addControl(new OverviewMap()); //+ sign in the lowerright to display the overviewmap
map.addControl(new ScaleLine()); //Display the scaleline
map.addControl(new MousePosition());

//Center and zoom to a location
LonLat lonLat = new LonLat(146.7, -41.8);
lonLat.transform(new Projection(ProjectionCode.LONGLAT.getEpsgCode()).getProjectionCode(),
map.getProjection()); //transform lonlat to OSM coordinate system
map.setCenter(lonLat, 6);
...


I used the example codes i found on this site:
http://demo.gwt-openlayers.org/gwt_ol_showcase/GwtOpenLayersShowcase.html

Anyone can try out because the wmsUrl points to the demo site.

The problem is that the WMS layer only appears when i zoom out to the outermost zoom level. Than if i try to zoom in, it disappears again. Any idea?

Answer

i've found a setting:

wmsLayerParams.setDisplayOutsideMaxExtent(true);

But i don't understand why isn't the true value the default...