Logo Questions Linux Laravel Mysql Ubuntu Git Menu
 

style multiple GeoJson files with the Google Maps Javascript API v3 data layer

I have a site that uses google api v3 for showing polygons from json files.

the site has multiple json polygons, I need to style each polygon with a different color and create a handle to the shape.

The only examples that I can find refer to pure polygons and not json files, there is one example that changes the json file (i cant do this as the json files are static.

sample code:

var map;

function initMap() {
    map = new google.maps.Map(document.getElementById('map'), {
        zoom: 4,
        center: { lat: 45, lng: -90 }
    });


//1st Json file
map.data.loadGeoJson(
        'https://storage.googleapis.com/mapsdevsite/json/google.json');

//2nd json file  (same as #1 for illustration purpose)
map.data.loadGeoJson(
        'https://storage.googleapis.com/mapsdevsite/json/google.json');

    // I want to style each Json file independently
    map.data.setStyle({
        fillColor: 'green',
        strokeWeight: 1
    });

   // map1.setMap(map);


}

I managed to get the layer added to the map using,

  data_layer.loadGeoJson('https://storage.googleapis.com/mapsdevsite/json/google.json');


    // Construct the polygon.
    var nLayer = new google.maps.JSON({
        paths: data_layer,
        strokeColor: 'green',
        strokeOpacity: 0.5,
        strokeWeight: 1,
        fillColor: 'green',
        fillOpacity: 0.8
    });

    nLayer.setMap(map);

I cannot get the style to apply to the map. any ideas ?

like image 567
user2668812 Avatar asked Aug 23 '16 16:08

user2668812


People also ask

How do I import GeoJSON into Google Maps?

Loading data from the same domain The Google Maps Data Layer provides a container for arbitrary geospatial data (including GeoJSON). If your data is in a file hosted on the same domain as your Maps JavaScript API application, you can load it using the map. data. loadGeoJson() method.

Does Google Maps use GeoJSON?

GeoJSON is a common standard for sharing geospatial data on the internet. It is lightweight and easily human-readable, making it ideal for sharing and collaborating. With the Data layer, you can add GeoJSON data to a Google map in just one line of code. map.

What is a GeoJSON layer?

GeoJSON is an open standard geospatial data interchange format that represents simple geographic features and their nonspatial attributes. Based on JavaScript Object Notation (JSON), GeoJSON is a format for encoding a variety of geographic data structures.


2 Answers

I have created a demo on github where I load polygons (boundaries) using Data Layer and I also show how to keep reference to respective polygons and update their specific styles. Check out this SO answer for a snippet (I don't want to copy it here, because it's redundant).

Notice mainly: new_boundary.feature = data_layer.getFeatureById(boundary_id); where I store reference to specific feature, which styles I can update anytime using e.g.:

data_layer.overrideStyle(new_boundary.feature, {
    fillColor: '#0000FF',
    fillOpacity: 0.9
});

And it would just update that one polygon, not all of them. So if your polygons in geoJSON files have some unique ids, or you can assign ids to all of them, you can then reference and change their styles based on that.

Another option, not shown in the example is, to have multiple data layers. It's possible to have multiple data layers in your application, e.g. create them like this:

var data_layer = new google.maps.Data({map: map});
var data_layer_2 = new google.maps.Data({map: map});

and then load data to them and change styles:

data_layer.loadGeoJson(
    'https://storage.googleapis.com/mapsdevsite/json/google.json');
data_layer_2.loadGeoJson(
    'https://storage.googleapis.com/mapsdevsite/json/google.json');
data_layer.setStyle({
    fillColor: 'green',
    strokeWeight: 1
});
data_layer_2.setStyle({
    fillColor: 'blue',
    strokeWeight: 2
});
like image 54
Matej P. Avatar answered Oct 05 '22 10:10

Matej P.


I think the best way to do this is to add a property to your feature, inside the json file you load, like so:

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {
        "county": "hernando"
      },
      "geometry": {
        "type": "MultiPolygon",
        "coordinates": [
          [
            [
              [
                -82.7784371,
                28.694206
              ],
              [
                -82.778214,
                28.6939659
              ],
            ]
          ]
        ]
      }
    }
  ]
}

Note the important part:

"properties": {
   "county": "hernando"
},

Each one of your json files can have as many properties as you want

Then in your javascript file, you can do something like this:

var map = new google.maps.Map($el[0], args);

map.data.loadGeoJson(
  '/wp-content/themes/hello-theme-child-master/county-json/pinellas.json'
);
map.data.loadGeoJson(
  '/wp-content/themes/hello-theme-child-master/county-json/pasco.json'
);
map.data.loadGeoJson(
  '/wp-content/themes/hello-theme-child-master/county-json/hillsborough.json'
);

map.data.setStyle( function ( feature ) {
  var county = feature.getProperty('county');
  var color = '';

  if ( county === 'pasco ) {
    color = 'orange'
  }
  else { 
    color = 'green'
  }

  return {
    fillColor: color,
    strokeWeight: 1
  };
});

The important part to note there is that you must pass a function to setStyle, so that it automatically iterates through every feature

like image 43
Nate Beers Avatar answered Oct 05 '22 10:10

Nate Beers