geojson 0.4.0

Manipulate geojson data. Load and parse geojson from a string or a file.

Geojson

Utilities to work with geojson data in Dart. Features:

• Parser: simple functions are available to parse geojson
• Reactive api: streams are available to retrieve the geojson features as soon as they are parsed

Note: the data is parsed in an isolate to avoid slowing down the main thread

Simple functions

featuresFromGeoJson: get a FeaturesCollection from geojson string data. Parameters:

• data: a string with the geojson data, required
• nameProperty: the property used for the geoserie name, automaticaly set if null
• verbose: print the parsed data if true

featuresFromGeoJsonFile: get a FeaturesCollection from a geojson file. Parameters:

• file: the file to load, required
• nameProperty: the property used for the geoserie name, automaticaly set if null
• verbose: print the parsed data if true

Reactive api

Typed streams are available to retrieve the features as soon as they are parsed. Example: add assets on a Flutter map:

  import 'dart:math' as math;
  import 'package:pedantic/pedantic.dart';
  import 'package:flutter/services.dart' show rootBundle;
  import 'package:geojson/geojson.dart';
  import 'package:flutter_map/flutter_map.dart' as map;

  /// Data for the Flutter map polylines layer
  final lines = <map.Polyline>[];

  Future<void> processData() async {
    final data = await rootBundle
        .loadString('assets/railroads_of_north_america.geojson');
    final geojson = GeoJson();
    geojson.processedLines.listen((Line line) {
      final color = Color((math.Random().nextDouble() * 0xFFFFFF).toInt() << 0)
          .withOpacity(0.3);
      setState(() => lines.add(map.Polyline(
          strokeWidth: 2.0, color: color, points: line.geoSerie.toLatLng())));
    });
    geojson.endSignal.listen((_) => geojson.dispose());
    unawaited(geojson.parse(data, verbose: true));
  }

Check the examples for more details

Available streams:

• processedFeatures: the parsed features: all the geometries
• processedPoints: the parsed points
• processedMultipoints: the parsed multipoints
• processedLines: the parsed lines
• processedMultilines: the parsed multilines
• processedPolygons: the parsed polygons
• processedMultipolygons: the parsed multipolygons
• endSignal: parsing is finished indicator

Supported geojson features

All the data structures use GeoPoint and GeoSerie from the GeoPoint package to store the geometry data. Data structures used:

FeatureCollection:

• String name
• List<Feature> collection

Feature:

• FeatureType type: one of FeatureType.point, FeatureType.multipoint, FeatureType.line, FeatureType.multiline, FeatureType.polygon, FeatureType.multipolygon
• Map<String, dynamic> properties: the json properties of the feature
• dynamic geometry: the geometry data, depends on the feature type, see below

Point:

• String name
• GeoPoint geoPoint: the geometry data

MultiPoint:

• String name
• GeoSerie geoSerie: the geometry data: this will produce a geoSerie of type GeoSerieType.group

Line:

• String name
• GeoSerie geoSerie: the geometry data: this will produce a geoSerie of type GeoSerieType.line

MultiLine:

• String name
• List<Line> lines

Polygon:

• String name
• List<GeoSerie> geoSeries: the geometry data: this will produce a list of geoSerie of type GeoSerieType.polygon*

MultiPolygon:

• String name
• List<Polygon> polygons

Note: none of the parameters is final for all of these data structures