geojson 0.9.1

Dart native
Flutter Android iOS

Utilities to work with geojson data. Parser with a reactive api, search and geofencing

Geojson #

pub package Build Status Coverage Status

Utilities to work with geojson data in Dart. Features:

  • Parser with a reactive api: streams are available to retrieve the geojson features as soon as they are parsed
  • Search: search for properties
  • Geofencing: geofence points in a polygon or from a distance

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

These functions are suitable for small data. Example:

final features = await featuresFromGeoJson(data);

Web support #

featuresFromGeoJsonMainThread: as the web do not support isolates use this function to parse in the main thread. 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

Reactive api #

Parse and listen #

Typed streams are available to retrieve the features as soon as they are parsed. This is useful when the data is big.

  • 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

Example: add assets on a Flutter map:

  import 'package:flutter/services.dart' show rootBundle;
  import 'package:geojson/geojson.dart';
  import 'package:flutter_map/flutter_map.dart';

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

  Future<void> parseAndDrawAssetsOnMap() async {
    final geo = GeoJson();
    geo.processedLines.listen((GeoJsonLine line) {
      /// when a line is parsed add it to the map right away
      setState(() => lines.add(Polyline(
          strokeWidth: 2.0, color: Colors.blue, points: line.geoSerie.toLatLng())));
    });
    geo.endSignal.listen((_) => geo.dispose());
    final data = await rootBundle
        .loadString('assets/railroads_of_north_america.geojson');
    await geo.parse(data, verbose: true);
  }

Data properties #

After the data is parsed the GeoJson instance has properties to access the data:

List<GeoJsonFeature> features;
List<GeoJsonPoint> points;
List<GeoJsonMultiPoint> multipoints;
List<GeoJsonLine> lines;
List<GeoJsonMultiLine> multilines;
List<GeoJsonPolygon> polygons;
List<GeoJsonMultiPolygon> multipolygons;

Example:

final List<GeoJsonLine> lines = geo.lines;

Search in a geojson file:

final geo = GeoJson();
await geo.searchInFile("countries.geojson",
    query: GeoJsonQuery(
        geometryType: GeoJsonFeatureType.multipolygon,
        matchCase: false,
        property: "name",
        value: "Zimbabwe"),
    verbose: true);
List<GeoJsonMultiPolygon> result = geo.multipolygons;

A search method is also available, taking string data in parameter instead of a file path. The streams are available to retrieve the data as soon as it is found

Geofencing #

Geofence points within a distance of a given point:

   final geo = GeoJson();
   /// `point` is the [GeoJsonPoint] to search from
   /// `points` is the list of [GeoJsonPoint] to search in
   /// `distance` is the distance to search in meters
   await geo.geofenceDistance(
         point: point, points: points, distance: distance);
    List<GeoPoint> foundPoints = geo.points;

Geofence points in a polygon:

   final geo = GeoJson();
   /// `polygon` is the [GeoJsonPolygon] to check
   /// `points` is the list of [GeoJsonPoint] to search in
   await geo.geofencePolygon(polygon: polygon, points: points);
    List<GeoPoint> foundPoints = geo.points;

Note: the processedPoints stream is available to retrieve geofenced points as soon as they are found

Maps #

To draw geojson data on a map check the Map controller package

Supported geojson features #

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

GeoJsonFeatureCollection:

  • String name
  • List<GeoJsonFeature> collection

GeoJsonFeature:

  • GeoJsonFeatureType type: types

  • Map<String, dynamic> properties: the json properties of the feature

  • dynamic geometry: the geometry data, depends on the feature type, see below

GeoJsonPoint:

  • String name
  • GeoPoint geoPoint: the geometry data

GeoJsonMultiPoint:

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

GeoJsonLine:

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

GeoJsonMultiLine:

  • String name
  • List<GeoJsonLine> lines

GeoJsonPolygon:

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

GeoJsonMultiPolygon:

  • String name
  • List<GeoJsonPolygon> polygons

GeoJsonGeometryCollection:

  • String name
  • List<GeoJsonFeature> geometries

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

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Utilities to work with geojson data. Parser with a reactive api, search and geofencing

Repository (GitHub)
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Documentation

API reference

Uploader

ansterj@gmail.com

License

MIT (LICENSE)

Dependencies

extra_pedantic, geodesy, geopoint, iso, meta, pedantic

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