Legend in Flutter Maps (SfMaps)

2 Nov 202124 minutes to read

You can provide clear information on the data plotted on the map using legend.

Shape legend

You can show shape legend by setting the MapShapeLayer.legend property as MapLegend(MapElement.shape). By default, the legend item’s text is rendered based on the value of shapeDataField property. The default value of the legend property is null and hence the legend will not be shown by default.

late MapShapeSource _shapeSource;

@override
void initState() {
  super.initState();

  _shapeSource = MapShapeSource.asset(
    "assets/world_map.json",
    shapeDataField: "continent",
  );
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: SizedBox(
          height: 350,
          child: Padding(
            padding: const EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend(MapElement.shape),
                ),
              ],
            ),
          ),
        ),
      ),
   );
}

Shape legend support

NOTE

Bubble legend

You can show bubble legend by setting the MapShapeLayer.legend property as MapLegend(MapElement.bubble). By default, the legend item’s text is rendered based on the value of shapeDataField property.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
  super.initState();
  _data = <Model>[
    Model('Asia', 150),
    Model('Africa', 45),
    Model('Europe', 34),
    Model('North America', 28),
    Model('South America', 25),
    Model('Australia', 5),
  ];

  _shapeSource = MapShapeSource.asset(
    "assets/world_map.json",
    shapeDataField: "continent",
    dataCount: _data.length,
    primaryValueMapper: (int index) => _data[index].continent,
    bubbleSizeMapper: (int index) => _data[index].populationDensityPerSqKm,
  );
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: Center(
      child: Container(
        padding: const EdgeInsets.only(left: 10, right: 15, top: 30),
        height: 350,
        child: SfMaps(
          layers: [
            MapShapeLayer(
              source: _shapeSource,
              legend: MapLegend(MapElement.bubble),
              bubbleSettings: const MapBubbleSettings(
                maxRadius: 45,
                minRadius: 15,
              ),
            )
          ],
        ),
      ),
    ),
  );
}

class Model {
  const Model(this.continent, this.populationDensityPerSqKm);

  final String continent;
  final double populationDensityPerSqKm;
}

Bubble legend support

NOTE

Bar shape legend

You can show bar shape legend by setting the MapShapeLayer.legend property as MapLegend.bar(MapElement.shape). By default, the legend item’s text is rendered based on the value of shapeDataField property.

late MapShapeSource _shapeSource;

@override
void initState() {
  super.initState();

  _shapeSource = MapShapeSource.asset(
    "assets/world_map.json",
    shapeDataField: "continent",
  );
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: const EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend.bar(MapElement.shape),
                ),
              ],
            ),
          ),
        ),
      ),
   );
}

Bar shape legend

NOTE

  • Refer the MapLegend, for showing default legend.

Bar bubble legend

You can show bar bubble legend by setting the MapShapeLayer.legend property as MapLegend.bar(MapElement.bubble). By default, the legend item’s text is rendered based on the value of shapeDataField property.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
  super.initState();
  _data = <Model>[
    Model('Asia', 150),
    Model('Africa', 45),
    Model('Europe', 34),
    Model('North America', 28),
    Model('South America', 25),
    Model('Australia', 5),
  ];

  _shapeSource = MapShapeSource.asset(
    "assets/world_map.json",
    shapeDataField: "continent",
    dataCount: _data.length,
    primaryValueMapper: (int index) => _data[index].continent,
    bubbleSizeMapper: (int index) => _data[index].populationDensityPerSqKm,
  );
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: Center(
      child: Container(
        padding: const EdgeInsets.only(left: 10, right: 15, top: 30),
        height: 350,
        child: SfMaps(
          layers: [
            MapShapeLayer(
              source: _shapeSource,
              legend: MapLegend.bar(MapElement.bubble),
              bubbleSettings: const MapBubbleSettings(
                maxRadius: 45,
                minRadius: 15,
              ),
            )
          ],
        ),
      ),
    ),
  );
}

class Model {
  const Model(this.continent, this.populationDensityPerSqKm);

  final String continent;
  final double populationDensityPerSqKm;
}

Bar bubble legend

NOTE

  • Refer the MapLegend, for showing default legend.

Title

You can add title to the legend using the MapLegend.title property.

NOTE

It is applicable for both shape and bar legend.

late MapShapeSource _dataSource;
late List<DataModel> _data;

@override
void initState() {
   _data = const <DataModel>[
      DataModel('Asia', 280),
      DataModel('Europe', 120),
      DataModel('Africa', 40),
      DataModel('North America', 90),
      DataModel('South America', 190),
      DataModel('Australia', 210),
   ];

   _dataSource = MapShapeSource.asset(
      'assets/world_map.json',
      shapeDataField: 'continent',
      dataCount: _data.length,
      primaryValueMapper: (int index) => _data[index].continent,
   );
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: Column(
        children: [
          SfMaps(
            layers: <MapShapeLayer>[
              MapShapeLayer(
                source: _dataSource,
                legend: MapLegend(
                  MapElement.shape,
                  title: Text('Continents',
                      style:
                          TextStyle(fontSize: 14, fontWeight: FontWeight.bold)),
                ),
              ),
            ],
          ),
        ],
      ),
   );
}

class DataModel {
  const DataModel(this.continent, this.size);

  final String continent;
  final double size;
}

Legend title

Icon and text customization

The icons color of the legend is applied based on the colors returned from the MapShapeLayerDelegate.shapeColorValueMapper property and the text is taken from the shapeDataField. It is possible to customize the legend icons color and texts using the MapColorMapper.color and MapColorMapper.text properties based on the MapColorMapper.value or MapColorMapper.from and MapColorMapper.to properties.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
  super.initState();
  _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Russia', 310)
  ];

  _shapeSource = MapShapeSource.asset("assets/world_map.json",
        shapeDataField: "name",
        dataCount: _data.length,
        primaryValueMapper: (int index) => _data[index].country,
        shapeColorValueMapper: (int index) => _data[index].density,
        shapeColorMappers: [
          MapColorMapper(from: 0, to: 100, color: Colors.red, text: '< 100/km'),
          MapColorMapper(
              from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
          MapColorMapper(
              from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
          MapColorMapper(
              from: 301, to: 400, color: Colors.orange, text: '300 - 400/km'),
  ]);
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: const EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend(MapElement.shape),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Legend text customization

First segment label customization

You can customize the first segment label of the legend using the MapColorMapper.text property with curly braces. The first curly brace value will be applied as segment start label and the next curly brace value will be applied as segment end label. By default, the MapColorMapper.from value is placed at the starting position of first segment and the MapColorMapper.to value is placed at the ending position of the first segment.

late List<DataModel> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
  _data = <DataModel>[
    DataModel('India', 280),
    DataModel('United States of America', 190),
    DataModel('Kazakhstan', 37),
    DataModel('Italy', 201),
    DataModel('Japan', 335),
    DataModel('Cuba', 103),
    DataModel('China', 148)
  ];

  _shapeSource = MapShapeSource.asset(
    "assets/world_map.json",
    shapeDataField: "name",
    dataCount: _data.length,
    primaryValueMapper: (int index) => _data[index].country,
    shapeColorValueMapper: (int index) => _data[index].density,
    shapeColorMappers: [
      MapColorMapper(
          from: 0, to: 100, color: Colors.red, text: '{0/km},{100/km}'),
      MapColorMapper(from: 101, to: 200, color: Colors.green, text: '200/km'),
      MapColorMapper(from: 201, to: 300, color: Colors.blue, text: '300/km'),
      MapColorMapper(from: 301, to: 400, color: Colors.orange, text: '400/km'),
      MapColorMapper(from: 401, to: 500, color: Colors.teal, text: '500/km'),
    ],
  );
  super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: Center(
      child: Container(
        height: 350,
        child: Padding(
          padding: const EdgeInsets.only(left: 15, right: 15),
          child: SfMaps(
            layers: [
              MapShapeLayer(
                source: _shapeSource,
                legend: MapLegend.bar(
                  MapElement.shape,
                ),
              )
            ],
          ),
        ),
      ),
    ),
  );
}

class DataModel {
  const DataModel(this.country, this.density);

  final String country;
  final double density;
}

First label customization

Position

You can position the legend items in different directions using the MapLegend.position property. The default value of the position property is MapLegendPosition.top. The possible values are left, right, top, and bottom.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
  super.initState();
  _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Korea', 512),
      Model('Japan', 335),
      Model('Cuba', 103),
      Model('China', 148)
  ];

  _shapeSource = MapShapeSource.asset("assets/world_map.json",
        shapeDataField: "name",
        dataCount: _data.length,
        primaryValueMapper: (int index) => _data[index].country,
        shapeColorValueMapper: (int index) => _data[index].density,
        shapeColorMappers: [
          MapColorMapper(from: 0, to: 100, color: Colors.red, text: '< 100/km'),
          MapColorMapper(
              from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
          MapColorMapper(
              from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
          MapColorMapper(
              from: 301, to: 400, color: Colors.orange, text: '300 - 400/km'),
          MapColorMapper(
              from: 401, to: 500, color: Colors.teal, text: '400 - 500/km'),
          MapColorMapper(
              from: 501,
              to: 600,
              color: Colors.deepPurple,
              text: '500 - 600/km'),
    ]);
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: const EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend(
                    MapElement.shape,
                    position: MapLegendPosition.right,
                  ),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Legend position

NOTE

  • Refer the offset, for placing the legend in custom position.

Offset

You can place the legend in custom position using the MapLegend.offset property. The default value of the offset property is null.

If the property MapLegend.offset has been set with the property MapLegend.position as top, then the legend will be placed in top but with absolute position, i.e. legend will not take dedicated position for it and will be drawn at the top of the map.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
    super.initState();
    _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Korea', 512),
      Model('Japan', 335),
      Model('Cuba', 103),
      Model('China', 148)
    ];

    _shapeSource = MapShapeSource.asset("assets/world_map.json",
        shapeDataField: "name",
        dataCount: _data.length,
        primaryValueMapper: (int index) => _data[index].country,
        shapeColorValueMapper: (int index) => _data[index].density,
        shapeColorMappers: [
          MapColorMapper(from: 0, to: 100, color: Colors.red, text: '< 100/km'),
          MapColorMapper(
              from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
          MapColorMapper(
              from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
          MapColorMapper(
              from: 301, to: 400, color: Colors.orange, text: '300 - 400/km'),
          MapColorMapper(
              from: 401, to: 500, color: Colors.teal, text: '400 - 500/km'),
          MapColorMapper(
              from: 501,
              to: 600,
              color: Colors.deepPurple,
              text: '500 - 600/km'),
    ]);
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: const EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend(
                    MapElement.shape,
                    offset: Offset(60, 275)),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Legend offset

Overflow mode

For default legend

You can wrap or scroll the legend items using the MapLegend.overflowMode property. The default value of the overflowMode property is MapLegendOverflowMode.wrap. The possible values are scroll and wrap.

If the legend position is left or right, then the default scroll direction is vertical.

If the legend position is top or bottom, then the default scroll direction is horizontal.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
   super.initState();
   _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Korea', 512),
      Model('Japan', 335),
      Model('Cuba', 103),
      Model('China', 148)
   ];

   _shapeSource = MapShapeSource.asset("assets/world_map.json",
        shapeDataField: "name",
        dataCount: _data.length,
        primaryValueMapper: (int index) => _data[index].country,
        shapeColorValueMapper: (int index) => _data[index].density,
        shapeColorMappers: [
          MapColorMapper(from: 0, to: 100, color: Colors.red, text: '< 100/km'),
          MapColorMapper(
              from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
          MapColorMapper(
              from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
          MapColorMapper(
              from: 301, to: 400, color: Colors.orange, text: '300 - 400/km'),
          MapColorMapper(
              from: 401, to: 500, color: Colors.teal, text: '400 - 500/km'),
          MapColorMapper(
              from: 501,
              to: 600,
              color: Colors.deepPurple,
              text: '500 - 600/km'),
        ]);
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: const EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend(
                    MapElement.shape,
                    position: MapLegendPosition.bottom,
                    overflowMode: MapLegendOverflowMode.scroll,
                  ),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Legend overflow mode

For bar legend

You can wrap or scroll the bar legend items using the MapLegend.overflowMode property. The default value of the overflowMode property is MapLegendOverflowMode.scroll. The possible values are scroll and wrap.

If the legend position is left or right, then the default scroll direction is vertical.

If the legend position is top or bottom, then the default scroll direction is horizontal.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
   super.initState();
   _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Korea', 512),
      Model('Japan', 335),
      Model('Cuba', 103),
      Model('China', 148)
   ];

   _shapeSource = MapShapeSource.asset("assets/world_map.json",
        shapeDataField: "name",
        dataCount: _data.length,
        primaryValueMapper: (int index) => _data[index].country,
        shapeColorValueMapper: (int index) => _data[index].density,
        shapeColorMappers: [
          MapColorMapper(from: 0, to: 100, color: Colors.red, text: '< 100/km'),
          MapColorMapper(
              from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
          MapColorMapper(
              from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
          MapColorMapper(
              from: 301, to: 400, color: Colors.orange, text: '300 - 400/km'),
          MapColorMapper(
              from: 401, to: 500, color: Colors.teal, text: '400 - 500/km'),
          MapColorMapper(
              from: 501,
              to: 600,
              color: Colors.deepPurple,
              text: '500 - 600/km'),
        ]);
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: const EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend.bar(
                    MapElement.shape,
                    position: MapLegendPosition.bottom,
                    edgeLabelsPlacement: MapLegendEdgeLabelsPlacement.center,
                    overflowMode: MapLegendOverflowMode.scroll,
                  ),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Bar legend overflow mode

NOTE

  • Refer the iconSize, for setting the size of the icon.

Legend toggling

NOTE

Legend toggling is not applicable for bar type legend.

You can enable toggling the legend items and the corresponding shapes or bubbles using the enableToggleInteraction argument in the constructor. The default value of the enableToggleInteraction argument in the constructor is false. You can customize the toggled shapes or bubbles using the following properties:

  • Toggled item color - Change the color for the toggled legend item’s icon and it’s shape or bubble using the toggledItemColor argument in the constructor.
  • Toggled item stroke color - Change the stroke color which applies to the toggled legend item’s shape or bubble using the toggledItemStrokeColor argument in the constructor.
  • Toggled item stroke width - Change the stroke width which applies to the toggled legend item’s shape or bubble using the toggledItemStrokeWidth argument in the constructor.
  • Toggled item opacity - Change the opacity of the toggled legend item’s shape or bubble using the toggledItemOpacity argument in the constructor.
late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
   super.initState();
   _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Korea', 512),
      Model('Japan', 335),
      Model('Cuba', 103),
      Model('China', 148)
   ];

   _shapeSource = MapShapeSource.asset("assets/world_map.json",
        shapeDataField: "name",
        dataCount: _data.length,
        primaryValueMapper: (int index) => _data[index].country,
        shapeColorValueMapper: (int index) => _data[index].density,
        shapeColorMappers: [
          MapColorMapper(from: 0, to: 100, color: Colors.red, text: '< 100/km'),
          MapColorMapper(
              from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
          MapColorMapper(
              from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
          MapColorMapper(
              from: 301, to: 400, color: Colors.orange, text: '300 - 400/km'),
          MapColorMapper(
              from: 401, to: 500, color: Colors.teal, text: '400 - 500/km'),
          MapColorMapper(
              from: 501,
              to: 600,
              color: Colors.deepPurple,
              text: '500 - 600/km'),
    ]);
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: const EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend(
                    MapElement.shape,
                    enableToggleInteraction: true,
                    toggledItemColor: Colors.grey,
                    toggledItemStrokeWidth: 3,
                    toggledItemStrokeColor: Colors.black,
                  ),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Using SfMapsTheme

You can also customize the below appearance of the legend using SfMapsTheme.

NOTE

You must import the theme.dart library from the Core package to use SfMapsTheme.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
    super.initState();
    _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Korea', 512),
      Model('Japan', 335),
      Model('Cuba', 103),
      Model('China', 148)
   ];

   _shapeSource = MapShapeSource.asset("assets/world_map.json",
        shapeDataField: "name",
        dataCount: _data.length,
        primaryValueMapper: (int index) => _data[index].country,
        shapeColorValueMapper: (int index) => _data[index].density,
        shapeColorMappers: [
          MapColorMapper(from: 0, to: 100, color: Colors.red, text: '< 100/km'),
          MapColorMapper(
              from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
          MapColorMapper(
              from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
          MapColorMapper(
              from: 301, to: 400, color: Colors.orange, text: '300 - 400/km'),
          MapColorMapper(
              from: 401, to: 500, color: Colors.teal, text: '400 - 500/km'),
          MapColorMapper(
              from: 501,
              to: 600,
              color: Colors.deepPurple,
              text: '500 - 600/km'),
    ]);
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: const EdgeInsets.only(left: 15, right: 15),
            child: SfMapsTheme(
              data: SfMapsThemeData(
                toggledItemColor: Colors.grey,
                toggledItemStrokeWidth: 3,
                toggledItemStrokeColor: Colors.black,
              ),
              child: SfMaps(
                layers: [
                  MapShapeLayer(
                    source: _shapeSource,
                    legend: MapLegend(
                      MapElement.shape,
                      enableToggleInteraction: true,
                    ),
                  )
                ],
              ),
            ),
          ),
        ),
      ),
   );
}

class Model {
   Model(this.country, this.density);

   final String country;
   final double density;
}

Toggles legend items

Text style

You can customize the legend item’s text style using the MapLegend.textStyle property.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
    super.initState();
    _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Korea', 512),
      Model('Japan', 335),
      Model('Cuba', 103),
      Model('China', 148)
   ];

   _shapeSource = MapShapeSource.asset("assets/world_map.json",
        shapeDataField: "name",
        dataCount: _data.length,
        primaryValueMapper: (int index) => _data[index].country,
        shapeColorValueMapper: (int index) => _data[index].density,
        shapeColorMappers: [
          MapColorMapper(from: 0, to: 100, color: Colors.red, text: '< 100/km'),
          MapColorMapper(
              from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
          MapColorMapper(
              from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
          MapColorMapper(
              from: 301, to: 400, color: Colors.orange, text: '300 - 400/km'),
          MapColorMapper(
              from: 401, to: 500, color: Colors.teal, text: '400 - 500/km'),
          MapColorMapper(
              from: 501,
              to: 600,
              color: Colors.deepPurple,
              text: '500 - 600/km'),
        ]);
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: const EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend(
                    MapElement.shape,
                    textStyle: const TextStyle(
                        color: Colors.red,
                        fontSize: 16,
                        fontWeight: FontWeight.bold,
                        fontStyle: FontStyle.italic,
                        fontFamily: 'Times'
                    ),
                  ),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  Model(this.country, this.density);

  final String country;
  final double density;
}

Using SfMapsTheme

You can also customize the legend item’s text style using the SfMapsThemeData.legendTextStyle property in SfMapsTheme.

NOTE

You must import the theme.dart library from the Core package to use SfMapsTheme.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
    super.initState();
    _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Korea', 512),
      Model('Japan', 335),
      Model('Cuba', 103),
      Model('China', 148)
   ];

   _shapeSource = MapShapeSource.asset("assets/world_map.json",
        shapeDataField: "name",
        dataCount: _data.length,
        primaryValueMapper: (int index) => _data[index].country,
        shapeColorValueMapper: (int index) => _data[index].density,
        shapeColorMappers: [
          MapColorMapper(from: 0, to: 100, color: Colors.red, text: '< 100/km'),
          MapColorMapper(
              from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
          MapColorMapper(
              from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
          MapColorMapper(
              from: 301, to: 400, color: Colors.orange, text: '300 - 400/km'),
          MapColorMapper(
              from: 401, to: 500, color: Colors.teal, text: '400 - 500/km'),
          MapColorMapper(
              from: 501,
              to: 600,
              color: Colors.deepPurple,
              text: '500 - 600/km'),
        ]);
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: const EdgeInsets.only(left: 15, right: 15),
            child: SfMapsTheme(
              data: SfMapsThemeData(
                legendTextStyle: TextStyle(
                    color: Colors.red,
                    fontSize: 16,
                    fontWeight: FontWeight.bold,
                    fontStyle: FontStyle.italic,
                    fontFamily: 'Times'
                ),
              ),
              child: SfMaps(
                layers: [
                  MapShapeLayer(
                    source: _shapeSource,
                    legend: MapLegend(MapElement.shape),
                  )
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Legend text style

Default legend appearance customization

You can customize the legend items using the following properties.

  • iconType - Used to change the icon shape. The default value of the iconType argument in the constructor is MapIconType.circle. The possible values are circle, rectangle, triangle, and diamond.
  • iconSize - Used to change the size of the icon. The default value of iconSize argument in the constructor is Size(12.0, 12.0).
  • spacing - Used to provide space between the each legend items. The default value of the spacing argument in the constructor is 10.0.
  • direction - Used to arrange the legend items in either horizontal or vertical direction. The default value of direction property is horizontal, if the value of the position property is top, bottom and defaults to vertical, if the value of the position property is left or right.
  • padding - Used to set padding around the legend. The default value of the padding property is EdgeInsets.all(10.0).
late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
    super.initState();
    _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Korea', 512),
      Model('Japan', 335),
      Model('Cuba', 103),
      Model('China', 148)
    ];

    _shapeSource = MapShapeSource.asset("assets/world_map.json",
        shapeDataField: "name",
        dataCount: _data.length,
        primaryValueMapper: (int index) => _data[index].country,
        shapeColorValueMapper: (int index) => _data[index].density,
        shapeColorMappers: [
          MapColorMapper(from: 0, to: 100, color: Colors.red, text: '< 100/km'),
          MapColorMapper(
              from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
          MapColorMapper(
              from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
          MapColorMapper(
              from: 301, to: 400, color: Colors.orange, text: '300 - 400/km'),
          MapColorMapper(
              from: 401, to: 500, color: Colors.teal, text: '400 - 500/km'),
          MapColorMapper(
              from: 501,
              to: 600,
              color: Colors.deepPurple,
              text: '500 - 600/km'),
        ]);
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: const EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend(
                    MapElement.shape,
                    position: MapLegendPosition.bottom,
                    overflowMode: MapLegendOverflowMode.wrap,
                    iconType: MapIconType.square,
                    iconSize: Size(15.0, 15.0),
                    itemsSpacing: 15,
                  ),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Legend items customization

NOTE

  • Refer the position, for setting the position of the legend.

Bar legend segment painting style

Solid

You can set solid color for the bar by using the MapLegendPaintingStyle.solid. By defaults MapLegendPaintingStyle will be solid.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
   super.initState();
   _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Korea', 512),
      Model('Japan', 335),
      Model('Cuba', 103),
      Model('China', 148)
   ];

   _shapeSource = MapShapeSource.asset("assets/world_map.json",
        shapeDataField: "name",
        dataCount: _data.length,
        primaryValueMapper: (int index) => _data[index].country,
        shapeColorValueMapper: (int index) => _data[index].density,
        shapeColorMappers: [
          MapColorMapper(from: 0, to: 100, color: Colors.red, text: '< 100/km'),
          MapColorMapper(
              from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
          MapColorMapper(
              from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
          MapColorMapper(
              from: 301, to: 400, color: Colors.orange, text: '300 - 400/km'),
          MapColorMapper(
              from: 401, to: 500, color: Colors.teal, text: '400 - 500/km'),
          MapColorMapper(
              from: 501,
              to: 600,
              color: Colors.deepPurple,
              text: '500 - 600/km'),
        ]);
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend.bar(
                    MapElement.shape,
                    segmentPaintingStyle: MapLegendPaintingStyle.solid,
                  ),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Bar legend solid type

Gradient

You can set gradient color for the bar by using the MapLegendPaintingStyle.gradient.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
   super.initState();
   _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Korea', 512),
      Model('Japan', 335),
      Model('Cuba', 103),
      Model('China', 148)
   ];

    _shapeSource = MapShapeSource.asset("assets/world_map.json",
           shapeDataField: "name",
           dataCount: _data.length,
           primaryValueMapper: (int index) => _data[index].country,
           shapeColorValueMapper: (int index) => _data[index].density,
           shapeColorMappers: [
             MapColorMapper(from: 0, to: 100, color: Colors.red, text: '< 100/km'),
             MapColorMapper(
                 from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
             MapColorMapper(
                 from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
             MapColorMapper(
                 from: 301,
                 to: 600,
                 color: Colors.deepPurple,
                 text: '300 - 600/km'),
    ]);
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend.bar(
                    MapElement.shape,
                    labelsPlacement: MapLegendLabelsPlacement.betweenItems,
                    edgeLabelsPlacement: MapLegendEdgeLabelsPlacement.center,
                    segmentPaintingStyle: MapLegendPaintingStyle.gradient,
                  ),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Bar legend gradient type

Bar legend appearance customization

You can customize the legend items using the following properties.

  • segmentSize - Used to change the size of individual bar segments. When gradient paint style is applied, segmentSize argument in the constructor will update the whole bar.
  • labelOverflow - Used to remove or trim the legend labels based on the bar legend size.The default value of the labelOverflow argument in the constructor will be MapLabelOverflow.hide.
  • edgeLabelsPlacement - Used to place the edge labels either inside or outside of the bar legend. The default value of the edgeLabelsPlacement argument in the constructor will be MapLegendEdgeLabelsPlacement.inside.
  • spacing - Used to provide space between the each legend items. The default value of the spacing is 2.0. This is not applicable for gradient legend.
  • direction - Used to arrange the legend items in either horizontal or vertical direction. The default value of direction property is horizontal, if the value of the position property is top, bottom and defaults to vertical, if the value of the position property is left or right.
  • padding - Used to set padding around the legend. The default value of the padding property is EdgeInsets.all(10.0).
late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
   super.initState();
   _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Korea', 512),
      Model('Japan', 335),
      Model('Cuba', 103),
      Model('China', 148)
   ];

    _shapeSource = MapShapeSource.asset("assets/world_map.json",
           shapeDataField: "name",
           dataCount: _data.length,
           primaryValueMapper: (int index) => _data[index].country,
           shapeColorValueMapper: (int index) => _data[index].density,
           shapeColorMappers: [
             MapColorMapper(from: 0, to: 100, color: Colors.red, text: '< 100/km'),
             MapColorMapper(
                 from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
             MapColorMapper(
                 from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
             MapColorMapper(
                 from: 301,
                 to: 600,
                 color: Colors.deepPurple,
                 text: '300 - 600/km'),
    ]);
}

@override
Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend.bar(
                    MapElement.shape,
                    labelsPlacement: MapLegendLabelsPlacement.betweenItems,
                    edgeLabelsPlacement: MapLegendEdgeLabelsPlacement.center,
                    segmentPaintingStyle: MapLegendPaintingStyle.gradient,
                    labelOverflow: MapLabelOverflow.ellipsis,
                  ),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Bar legend customization

Bar legend labels placement

You can place the labels either between the segments or on the segments using the labelsPlacement property.

Labels placement for range color mapper

The labels are positioned between the segments when setting range color mapper without setting color mapper MapColorMapper.text property. The MapColorMapper.from value of the first item is positioned at starting point of the first segment and the MapColorMapper.to value of the first item is placed at the first segment end position. For other segments, the values of MapColorMapper.to is positioned as label between the other segments.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
  super.initState();
  _data = <Model>[
    Model('India', 280),
    Model('United States of America', 190),
    Model('Kazakhstan', 37),
    Model('Italy', 201),
    Model('Cuba', 103),
    Model('China', 148),
];

_shapeSource = MapShapeSource.asset("assets/world_map.json",
    shapeDataField: "name",
    dataCount: _data.length,
    primaryValueMapper: (int index) => _data[index].country,
    shapeColorValueMapper: (int index) => _data[index].density,
    shapeColorMappers: [
      MapColorMapper(from: 0, to: 100, color: Colors.red),
      MapColorMapper(
              from: 101, to: 200, color: Colors.green),
      MapColorMapper(
              from: 201, to: 300, color: Colors.blue),
    ]
  );
}

@override
Widget build(BuildContext context) {
  return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend.bar(
                    MapElement.shape,
                    labelsPlacement: MapLegendLabelsPlacement.betweenItems,
                    segmentPaintingStyle: MapLegendPaintingStyle.gradient,
                  ),
                )
              ],
            ),
          ),
        ),
     ),
  );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Bar legend labels placement

The labels are positioned between the segments when setting range color mapper along with setting color mapper MapColorMapper.text property. The MapColorMapper.from value of the first item is positioned at starting point of the first segment and the MapColorMapper.text value of the first item is placed at the first segment end position. For Other segments, the value of MapColorMapper.text is positioned as label between the segments.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
  super.initState();
  _data = <Model>[
    Model('India', 280),
    Model('United States of America', 190),
    Model('Kazakhstan', 37),
    Model('Italy', 201),
    Model('Cuba', 103),
    Model('China', 148),
  ];

  _shapeSource = MapShapeSource.asset("assets/world_map.json",
    shapeDataField: "name",
    dataCount: _data.length,
    primaryValueMapper: (int index) => _data[index].country,
    shapeColorValueMapper: (int index) => _data[index].density,
    shapeColorMappers: [
        MapColorMapper(from: 0, to: 100, color: Colors.red, text: '<100/km'),
        MapColorMapper(from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
        MapColorMapper(from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
    ]
  );
}

@override
Widget build(BuildContext context) {
  return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend.bar(
                    MapElement.shape,
                    labelsPlacement: MapLegendLabelsPlacement.betweenItems,
                    segmentPaintingStyle: MapLegendPaintingStyle.gradient,
                  ),
                )
              ],
            ),
          ),
        ),
     ),
  );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Bar legend labels placement

The labels are positioned at the center of the segments when setting the labelsPlacement property to MapLegendLabelsPlacement.onItem. The labels calculated based on the value of MapColorMapper.text property. If the value of MapColorMapper.text property is null, labels calculated based on the values of MapColorMapper.from and MapColorMapper.to properties.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
  super.initState();
  _data = <Model>[
    Model('India', 280),
    Model('United States of America', 190),
    Model('Kazakhstan', 37),
    Model('Italy', 201),
    Model('Cuba', 103),
    Model('China', 148),
];

_shapeSource = MapShapeSource.asset("assets/world_map.json",
    shapeDataField: "name",
    dataCount: _data.length,
    primaryValueMapper: (int index) => _data[index].country,
    shapeColorValueMapper: (int index) => _data[index].density,
    shapeColorMappers: [
        MapColorMapper(from: 0, to: 100, color: Colors.red, text: '<100/km'),
        MapColorMapper(from: 101, to: 200, color: Colors.green, text: '100 - 200/km'),
        MapColorMapper(from: 201, to: 300, color: Colors.blue, text: '200 - 300/km'),
    ]
  );
}

@override
Widget build(BuildContext context) {
  return Scaffold(
      body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend.bar(
                    MapElement.shape,
                    labelsPlacement: MapLegendLabelsPlacement.onItem,
                    edgeLabelsPlacement: MapLegendEdgeLabelsPlacement.center,
                    segmentPaintingStyle: MapLegendPaintingStyle.gradient,
                  ),
                )
              ],
            ),
          ),
        ),
     ),
  );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Bar legend labels placement

Labels placement for equal color mapper

The labelsPlacement option is not applicable for the shape/bubble applied with equal color mapper. By default, the labels are positioned at center of the segment.

late List<Model> _data;
late MapShapeSource _dataSource;

@override
void initState() {
  _data = <Model>[
    Model('India', "Low"),
    Model('United States of America', "High"),
    Model('Pakistan', "Low"),
    Model('Brazil', "Medium"),
  ];

   _dataSource = MapShapeSource.asset(
     "assets/world_map.json",
     shapeDataField: "name",
     dataCount: _data.length,
     primaryValueMapper: (int index) {
        return _data[index].country;
     },
     shapeColorValueMapper: (int index) {
       return _data[index].storage;
     },
     shapeColorMappers: [
        MapColorMapper(value: "Low", color: Colors.green),
        MapColorMapper(value: "Medium", color: Colors.blue),
        MapColorMapper(value: "High", color: Colors.red),
     ],
  );
  super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: Center(
       child: Container(
          height: 350,
          child: Padding(
            padding: EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: <MapShapeLayer>[
                MapShapeLayer(
                  source: _dataSource,
                  legend: MapLegend.bar(
                    MapElement.shape,
                    edgeLabelsPlacement: MapLegendEdgeLabelsPlacement.center,
                    segmentPaintingStyle: MapLegendPaintingStyle.gradient,
                  ),
                ),
              ],
            ),
          ),
        ),
     ),
  );
}

class Model {
  const Model(this.country, this.storage);

  final String country;
  final String storage;
}

Bar legend labels placement

Show pointer

You may show a pointer on the bar gradient legend while hovering over a shape or bubble using the showPointerOnHover property. The default value of the showPointerOnHover property is false.

NOTE

It is applicable for gradient type bar legend.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
   super.initState();
   _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Cuba', 103),
      Model('China', 148),
    ];

    _shapeSource = MapShapeSource.asset(
      "assets/world_map.json",
      shapeDataField: "name",
      dataCount: _data.length,
      primaryValueMapper: (int index) => _data[index].country,
      shapeColorValueMapper: (int index) => _data[index].density,
      shapeColorMappers: [
        MapColorMapper(from: 0, to: 100, color: Colors.red, text: '0 - 100'),
        MapColorMapper(
            from: 101, to: 200, color: Colors.green, text: '101 - 200'),
        MapColorMapper(
            from: 201, to: 300, color: Colors.blue, text: '201 - 300'),
      ],
    );
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend.bar(
                    MapElement.shape,
                    segmentPaintingStyle: MapLegendPaintingStyle.gradient,
                    showPointerOnHover: true,
                  ),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Bar legend pointer

Pointer builder

It returns a widget for the given value.

The pointer is used to indicate the exact color of the hovering shape or bubble on the legend segment.

The pointerBuilder will be called when the user interacts with the shapes or bubbles i.e., while tapping in touch devices and hovering in the mouse enabled devices.

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
   super.initState();
   _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Cuba', 103),
      Model('China', 148),
   ];

   _shapeSource = MapShapeSource.asset(
      "assets/world_map.json",
      shapeDataField: "name",
      dataCount: _data.length,
      primaryValueMapper: (int index) => _data[index].country,
      shapeColorValueMapper: (int index) => _data[index].density,
      shapeColorMappers: [
        MapColorMapper(from: 0, to: 100, color: Colors.red, text: '0 - 100'),
        MapColorMapper(
            from: 101, to: 200, color: Colors.green, text: '101 - 200'),
        MapColorMapper(
            from: 201, to: 300, color: Colors.blue, text: '201 - 300'),
     ],
   );
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend.bar(
                    MapElement.shape,
                    segmentPaintingStyle: MapLegendPaintingStyle.gradient,
                    showPointerOnHover: true,
                    pointerBuilder: (BuildContext context, dynamic value) {
                      return Icon(Icons.arrow_downward, size: 15);
                    },
                  ),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Bar legend custom pointer

Pointer customization

You can customize the size and color of the pointer using the pointerSize and pointerColor properties. The default value of the pointerSize property is Size(16, 12).

late List<Model> _data;
late MapShapeSource _shapeSource;

@override
void initState() {
   super.initState();
   _data = <Model>[
      Model('India', 280),
      Model('United States of America', 190),
      Model('Kazakhstan', 37),
      Model('Italy', 201),
      Model('Cuba', 103),
      Model('China', 148),
    ];

    _shapeSource = MapShapeSource.asset(
      "assets/world_map.json",
      shapeDataField: "name",
      dataCount: _data.length,
      primaryValueMapper: (int index) => _data[index].country,
      shapeColorValueMapper: (int index) => _data[index].density,
      shapeColorMappers: [
        MapColorMapper(from: 0, to: 100, color: Colors.red, text: '0 - 100'),
        MapColorMapper(
            from: 101, to: 200, color: Colors.green, text: '101 - 200'),
        MapColorMapper(
            from: 201, to: 300, color: Colors.blue, text: '201 - 300'),
      ],
   );
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: Center(
        child: Container(
          height: 350,
          child: Padding(
            padding: EdgeInsets.only(left: 15, right: 15),
            child: SfMaps(
              layers: [
                MapShapeLayer(
                  source: _shapeSource,
                  legend: MapLegend.bar(
                    MapElement.shape,
                    segmentPaintingStyle: MapLegendPaintingStyle.gradient,
                    showPointerOnHover: true,
                    pointerSize: Size(20, 20),
                    pointerColor: Colors.deepPurple,
                  ),
                )
              ],
            ),
          ),
        ),
      ),
   );
}

class Model {
  const Model(this.country, this.density);

  final String country;
  final double density;
}

Bar legend pointer customization

NOTE

You can refer to our Flutter Maps feature tour page for its groundbreaking feature representations. You can also explore our Flutter Maps Legend example that shows how to configure a Maps in Flutter.