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GeoJSON Module

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The GeoJSON module (mapbox-sdk-geojson) of the Mapbox Java SDK provides support for GeoJSON, an open standard file format for representing map data. Read the GeoJSON specification and the Mapbox Glossary's GeoJSON entry for more information about GeoJSON.

Import GeoJSON classes​

Below are import statements for some of the most commonly used GeoJSON geometry classes, along with Feature and FeatureCollection.

import com.mapbox.geojson.Point
import com.mapbox.geojson.MultiPoint
import com.mapbox.geojson.LineString
import com.mapbox.geojson.MultiLineString
import com.mapbox.geojson.Polygon
import com.mapbox.geojson.MultiPolygon
import com.mapbox.geojson.Feature
import com.mapbox.geojson.FeatureCollection

Geometries​

The Java SDK provides classes for all GeoJSON geometry types. Point, MultiPoint, LineString, MultiLineString, Polygon, MultiPolygon, and GeometryCollection all end up implementing the Geometry interface. This shared interface gives you flexibility as you work with the Java SDK and potentially other Mapbox SDKs for Android.

The Point object represents a single geographical coordinate. It contains two values, longitude and latitude, in that order. This order is the reverse of the LatLng object in the Mapbox Maps SDK for Android. If you're using the Maps SDK and the Java SDK together, you'll need to convert between Point and LatLng objects.

Point point = Point.fromLngLat(LONGITUDE, LATITUDE); // Java SDK

LatLng latLng = new LatLng(point.latitude(), point.longitude()); // Maps SDK

Point point = Point.fromLngLat(latLng.getLongitude(), latLng.getLatitude());

All geometry classes can be created via several different static methods. Always use a static method to create a GeoJSON geometry class.

Creating a single Polygon:

Polygon polygon = Polygon.fromLngLats(listOfPointList);

Polygon polygonFromOuterInner = Polygon.fromOuterInner(outerLineStringObject,innerLineStringObject);

Creating a single MultiLineString:

MultiLineString multiLineString = MultiLineString.fromLineString(singleLineString);

MultiLineString multiLineStringFromLngLat = MultiLineString.fromLngLats(listOfPointList);

MultiLineString multiLineStringFromJson = MultiLineString.fromJson(JSON_STRING);

Feature and FeatureCollection​

In the GeoJSON specification, a feature is an individual (or in some cases, a group of) points, lines, or polygons. Read more about features in the Mapbox Glossary. A group of features is called a feature collection.

The Java SDK's GeoJSON module also provides Feature and FeatureCollection classes. These classes can be combined with the various GeoJSON geometry classes.

Feature pointFeature = Feature.fromGeometry(Point.fromLngLat(LONGITUDE, LATITUDE));

Feature multiPointFeature = Feature.fromGeometry(MultiPoint.fromLngLats(listOfPoints));

FeatureCollection featureCollectionFromSingleFeature = FeatureCollection.fromFeature(pointFeature);

FeatureCollection featureCollection = FeatureCollection.fromFeatures(listOfFeatures);

FeatureCollection featureCollectionFromJson = FeatureCollection.fromJson(jsonString);

Cast to a specific geometry object​

A Feature's Geometry can be cast to a specific geometry object.

In the code below, a Feature is used to create a Polygon:

String polygonFeatureJson = "{
" +
    "      "type": "Feature",
" +
    "      "properties": {},
" +
    "      "geometry": {
" +
    "        "type": "Polygon",
" +
    "        "coordinates": [
" +
    "          [
" +
    "            [
" +
    "              -20.7421875,
" +
    "              38.8225909761771
" +
    "            ],
" +
    "            [
" +
    "              -22.8515625,
" +
    "              -36.03133177633187
" +
    "            ],
" +
    "            [
" +
    "              51.328125,
" +
    "              -36.597889133070204
" +
    "            ],
" +
    "            [
" +
    "              48.515625,
" +
    "              39.90973623453719
" +
    "            ],
" +
    "            [
" +
    "              -20.7421875,
" +
    "              38.8225909761771
" +
    "            ]
" +
    "          ]
" +
    "        ]
" +
    "      }
" +
    "    }";

Feature singleFeature = Feature.fromJson(polygonFeatureJson);

Polygon polygon = (Polygon) singleFeature.geometry();

Check a geometry type​

You can check a Feature's geometry type. In the code below, a log message would appear whenever a Feature is a Point:

FeatureCollection featureCollection = FeatureCollection.fromFeatures(featureList);
if (featureCollection.features() != null) {
  for (Feature singleFeature : featureCollection.features()) {
    if (singleFeature.geometry() instanceof Point) {
      Log.d(TAG, "is a Point geometry");
    }
  }
}

Use with the Maps SDK​

When installed with Maven, the Mapbox Maps SDK for Android includes the Java SDK's GeoJSON module, which means you don't have to explicitly declare the Java SDK module if you're already using the Maps SDK. If you install the Maps SDK via direct download, you will need to declare the Java SDK explicitly.

Because of the Maps SDK's dependency on the GeoJSON module, the Maps SDK has been developed to support the Geometry, Feature, and FeatureCollection classes.

GeoJSON updates​

The Java and Maps SDKs are often used together to create a Maps SDK GeoJsonSource with a Feature or FeatureCollection.

For example, here's how you can create a GeoJsonSource with a Feature and then add the GeoJsonSource to the map.

mapboxMap.getStyle(new Style.OnStyleLoaded() {
@Override
public void onStyleLoaded(@NonNull Style style) {

	// Create a list to store our line coordinates.
	List routeCoordinates = new ArrayList<Point>();
	routeCoordinates.add(Point.fromLngLat(-118.394391, 33.397676));
	routeCoordinates.add(Point.fromLngLat(-118.370917, 33.391142));

	// Create the LineString from the list of coordinates and then make a GeoJSON FeatureCollection so that you can add the line to our map as a layer.

	LineString lineString = LineString.fromLngLats(routeCoordinates);

	Feature feature = Feature.fromGeometry(lineString);

	GeoJsonSource geoJsonSource = new GeoJsonSource("geojson-source", feature);
	style.addSource(geoJsonSource);
}
});

You can also update a GeoJsonSource's GeoJSON data to visually update the data on the map. Rather than passing through a Feature or FeatureCollection in the source.setGeoJson() method, you can pass a Geometry object to setGeoJson() directly.

For example, here's how to set a GeoJsonSource's GeoJSON data with a LineString:

mapboxMap.getStyle(new Style.OnStyleLoaded() {
	@Override
	public void onStyleLoaded(@NonNull Style style) {

	  GeoJsonSource source = style.getSourceAs(sourceId);

	  if (source != null && directionsRoute.geometry() != null) {
	    source.setGeoJson(LineString.fromPolyline(directionsRoute.geometry(), PRECISION_6));
	  }
	}
});

Serialize and deserialize geometries​

There might be a situation where you want to pass geometry data from one part of your project to another. A common case is putting data into an Android Intent as you start a new activity.

The geometry classes all have fromJson() and toJson() static methods, which help with serialization. The formatted valid JSON String passed through the fromJson() method will create the geometry object. This fromJson() method also means you can use Gson or other serialization/deserialization strategies.

MultiPolygon multiLineStringFromJson = MultiPolygon.fromJson(JSON_STRING);

String multiPolygonString = multiPolygon.toJson();
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