I am trying to load a single vector layer and be able to turn on and off
visibility of individual features within that layer from a layer tree.
For example, load all the United States in one layer and turn on and off each
state from the layer tree.
I would like to display this as a grouped layer for organization. Here is what
I have come up with so far. Is there a better way to do this?
var layerList = new GeoExt.tree.LayerNode({
text: 'The United States',
expanded: true,
layer: usa, // refers to a vector layer using HTTP protocol to get
GeoJSON.
leaf: false,
children : [{
text: "Alabama",
leaf: true,
fid:1,
checked: false
},{
text: "Alaska",
leaf: true,
fid:2,
checked: false
}, {
//... load other fifty states
}]
});
var layerTree = new Ext.tree.TreePanel({
title: 'Map Layers',
root: layerList,
autoScroll:true,
listeners: {
'checkchange': function(node, checked){
var tempfid = node.attributes.fid;
if(checked){
node.parentNode.attributes.layer.getFeatureByFid(tempfid).renderIntent =
'default';
// I am setting visibility with renderIntent
because styles are reset when layer is redrawn form panning or zooming.
node.parentNode.attributes.layer.redraw();
}else{
node.parentNode.attributes.layer.getFeatureByFid(tempfid).renderIntent =
'delete';
node.parentNode.attributes.layer.redraw();
}
}
}
});
I can't load individual layers for each state because I intend to do this with
other layers and OpenLayers can only display so many layers at a time, also
requests would become very heavy.
I am also using featureserver for my requests which does not have built in
GetCapabilities functionality.
I have found an example in OpenLayers that achieves what I am trying to do
here:
http://gis.ibbeck.de/ginfo/apps/OLExamples/OL26/examples/select-feature-with-function.html
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