[Users] Base Layer Does Not Display on Initial Load

[Andreas Hocevar]

Hi,

the problem here is that you configure the OpenLayers map in the wrong mode. See below:

On Sep 23, 2010, at 21:43 , IT Intern wrote:

> Hello GeoExt users,
> 
> This one's gotten me totally stumped.  I have some base layers and a few wms overlays.  When my page loads it shows the base layer for a quick second and then goes blank as it loads my overlays.  It stays blank until I click the map, etc.  Then it displays properly.  I've Googled all sorts of things concerning this sort of issue and have come up with nothing that gives me a hint as to why this could be.  This never happened to me before until I started using GeoExt to display my map.  Is it something in code I must write for GeoExt or OpenLayers so that this doesnt happen?  It's driving me crazy!!!
> 
> Code:
> 
> //Base Layers
> 
>              var ghyb = new OpenLayers.Layer.Google(
>                     "Google Hybrid",
>                     {type: google.maps.MapTypeId.HYBRID, numZoomLevels: 20}
>                 );
> 
>             var gmap = new OpenLayers.Layer.Google(
>                     "Google Streets", // the default
>                     {numZoomLevels: 20},{visibility: true} 
>             );
> 
>             var osm = new OpenLayers.Layer.OSM();
> 
> //.....
> ....
> ....
> 
> var options = {
>                     controls: [new OpenLayers.Control.Navigation()],
>                     maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
>                     maxResolution: "auto",
>                     projection: new OpenLayers.Projection("EPSG:900913"),
>                     units: 'm',
>                     allOverlays: false
>             }
> 
> 
>             var map = new OpenLayers.Map('map', options);

Wrong! If at all, use the following instead:

              var map = new OpenLayers.Map(options);

You don't want to render the map at this point, so you have to configure it without a map div.


>             map.addLayers([gmap, ghyb, osm, all_chn, all_tib, chn_bridges, tib_bridges, chn_countys, tib_countys, chn_farms, tib_farms, chn_glaciers, tib_glaciers, chn_grazing, tib_grazing, chn_hwyCrew, tib_hwyCrew, chn_hospitals, tib_hospitals, chn_lakes, tib_lakes, chn_monastaries, tib_monastaries, chn_pass, tib_pass, chn_rivers, tib_rivers, chn_townships, tib_townships, chn_villages, tib_villages]);                    
> 
>             var mapPanel = new GeoExt.MapPanel({
>                 title: "Map",
>                 map: map,

Now the preferred way to configure a MapPanel would be to remove the "var map = ..." above entirely, and configure the map here:

                  map: options,
                  layers: [gmap, ghyb, osm, all_chn, all_tib, chn_bridges, tib_bridges, chn_countys, tib_countys, chn_farms, tib_farms, chn_glaciers, tib_glaciers, chn_grazing, tib_grazing, chn_hwyCrew, tib_hwyCrew, chn_hospitals, tib_hospitals, chn_lakes, tib_lakes, chn_monastaries, tib_monastaries, chn_pass, tib_pass, chn_rivers, tib_rivers, chn_townships, tib_townships, chn_villages, tib_villages]

Regards,
Andreas. 

>                 center: map.setCenter(new OpenLayers.LonLat(93.9, 29.53).transform(new OpenLayers.Projection("EPSG:4326"), map.getProjectionObject())),
>                 zoom: 9, 
>                 region: "center",
>                 bbar: [{
>                     xtype: "label",
>                     text: "Scale = 1 : "
>                 }],
>                 items: [{
>                     xtype: "gx_zoomslider",
>                     vertical: true,
>                     height: 300,
>                     x: 10,
>                     y: 20,
>                     plugins: new GeoExt.ZoomSliderTip()
>                 }]
>             });
>             
>             var layerRoot = new Ext.tree.TreeNode({
>                 text: "All Layers",
>                 expanded: true,
>                 autoLoad: true
>                 });
>             
> //Is there something to set here???
>                 layerRoot.appendChild(new GeoExt.tree.BaseLayerContainer({
>                 text: "Base Layers",
>                 map: map,
>                 layerStore: mapPanel.layers,
>                 expanded: true,
>                 autoLoad: true
>                 }));
> 
> //.....
> 
> Thank you very much, I appreciate any suggestions :),
>  
> elshae
> 
> 
> 
> _______________________________________________
> Users mailing list
> Users at geoext.org
> http://www.geoext.org/cgi-bin/mailman/listinfo/users



-- 
Andreas Hocevar
OpenGeo - http://opengeo.org/
Expert service straight from the developers.