I have noticed that OpenLayers will not "load" source unless it is assigned to a layer which is assigned to map .
This code does console.log()
with number of features in a KML layer:
const layer = new Heatmap({
source: new VectorSource({
url: file,
format: new KML({
extractStyles: false,
}),
}),
});
layer.getSource().on('change', function (evt: any) {
var source = evt.target;
if (source.getState() === 'ready') {
var numFeatures = source.getFeatures().length;
console.log('Count after change: ' + numFeatures);
}
});
this.map.addLayer(layer);
If I remove this line:
this.map.addLayer(layer);
it doesn't output anything. I have a feeling that OpenLayers ignores it as it is not used. Is there a way to force OpenLayers to load it?
(context - I would like to merge features coming from multiple sources into one thus I don't want to directly load them onto the map . I'd like them to load so I can get features and then merge these features into one array and then display this array on the map )
You can combine features from multiple files and formats by fetching the urls and using the format's readFeatures()
method
const vectorSource = new VectorSource();
const layer = new Heatmap({
source: vectorSource,
});
function loadFromUrl (url, format) {
fetch(url).then(function (response) {
response.text().then(function (result) {
vectorSouce.addFeatures(
format.readFeatures(result, {
dataProjection: 'EPSG:4326',
featureProjection: map.getView().getProjection(),
})
}
});
}
loadFromUrl(kmlFile, new KML({extractStyles: false}));
loadFromUrl(geojsonFile, new GeoJSON());
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