choropleth_map.dart

import 'dart:typed_data';
import 'package:flutter/material.dart';
import 'package:syncfusion_flutter_core/theme.dart';
import 'package:syncfusion_flutter_maps/maps.dart';

import '../consts.dart';
import '../data_classes.dart';

/// ChoroplethMap is a stateful widget that contains a choropleth map.
/// The map is created using the Syncfusion Flutter Maps library and
/// coordinates fetched from the server.
class ChoroplethMap extends StatefulWidget {
  const ChoroplethMap({
    Key? key,
    required this.relation,
    required this.measurements,
    required this.subdivisions,
    required this.onSelectionChanged,
  }) : super(key: key);

  final Uint8List relation;
  final List<Measurement> measurements;
  final List<SubDiv> subdivisions;
  final void Function(int selectedIndex) onSelectionChanged;

  @override
  ChoroplethMapState createState() => ChoroplethMapState();
}

class ChoroplethMapState extends State<ChoroplethMap> {
  int selectedIndex = -1;            // Subdivision/map tile index
  late MapShapeSource dataSource;
  late final MapZoomPanBehavior _zoomPanBehavior = MapZoomPanBehavior();

  void updateDataSource() {
    _initDataSource();
  }

  @override
  void initState() {
    super.initState();
      selectedIndex = 0;
      _initDataSource();
    }

    void _initDataSource() {
      dataSource = MapShapeSource.memory(
        widget.relation,
        shapeDataField: 'sub_div_id',
        dataCount: widget.subdivisions.length,
        primaryValueMapper: (int index) => widget.subdivisions[index].sub_div_id,
        shapeColorValueMapper: (int index) => widget.subdivisions[index].color,
        shapeColorMappers: const [
          MapColorMapper(
              from: 0,
              to: 1,
              color: Color(0xffff0000),
              text: '{0},{1}'),
          MapColorMapper(
              from: 1,
              to: 2,
              color: Color(0xffff6a00),
              text: '2'),
          MapColorMapper(
              from: 2,
              to: 3,
              color: Color(0xFFb1ff00),
              text: '3'),
          MapColorMapper(
              from: 3,