Manipulate GeoJSON Data - reload vector Layer in OpenLayers

问题

I’m stuck on creating a function that manipulates loaded GeoJSON data and updates the OpenLayers Map. What I have so far is a map that works with data filtered from a loaded GeoJSON file. How do I change the vector layer to use updated data?

That’s my code so far:

load GeoJSON fullGeoJSON:

var fullGeoJSON = require("./data/data.json");

create var filteredGeoJSON

var filteredGeoJSON = {
    "type": "FeatureCollection",
    "features": []
};

fill empty features by filtering the fullGeoJSON

function filterGeoJSON(religion, gender) {
    fullGeoJSON.features.forEach(function (feature) {
        if (
            feature.properties.religion == religion &&
            feature.properties.gender == gender
        ) {
            filteredGeoJSON.features.push(feature);
        }
    });
}

define a vector source

var filteredSource = new VectorSource({
    features: new GeoJSON().readFeatures(filteredGeoJSON, {
        featureProjection: "EPSG:3857"
    })
});

define new vector layer using the source

var filteredLayer = new VectorLayer({
    source: filteredSource
});

define map (mainMap) using the vector source. The Map renders fine with only the features shown that are left over after filtering the input JSON

Now I’m looking for a way to change the filteredGeoJSON by the click of a button by calling filterGeoJSON() with different parameters and use this changed data source for refreshing the filteredSource and hence the filteredLayer. What I have so far is:

onClick("gender", function () {
    // clear filteredGeoJSON
    (filteredGeoJSON = {
        type: "FeatureCollection",
        features: []
    });
    filterGeoJSON("protestantisch", "f"); // call filterGeoJSON again
    mainMap.refresh(); // <- Something like this?
});

How do I force OpenLayers to use the changed filteredGeoJSON from the onClick function as the datasource for my mainMap?

Thanks for your help!

回答1:

You have to change the layer´s source to refresh the map´s content:

onClick("gender", function() {
   // clear filteredGeoJSON
   filteredGeoJSON = {
      type: "FeatureCollection",
      features: []
   };
   filteredSource = new VectorSource({
      features: filterGeoJSON("protestantisch", "f")
   })
  filteredLayer.setSource(filteredSource);
})

See here.

来源：https://stackoverflow.com/questions/53345234/manipulate-geojson-data-reload-vector-layer-in-openlayers

标签

javascript

OpenLayers

geojson