Legend in Flutter Treemap (SfTreemap)

5 May 202124 minutes to read

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

Enable default legend

You can show legend by initializing the SfTreemap.legend property. By default, the legend item’s text is rendered based on the value of TreemapLevel.groupMapper property. The default value of the legend property is null and hence the legend will not be shown by default.

late List<SocialMediaUsers> _source;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
          ),
        ],
        legend: TreemapLegend(),
     ),
  );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

default legend

NOTE

Bar shape legend

You can show bar shape legend by initializing the SfTreemap.legend property as TreemapLegend.bar. By default, the legend item’s text is rendered based on the value of TreemapLevel.groupMapper property.

late List<SocialMediaUsers> _source;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
          ),
        ],
        legend: TreemapLegend.bar(),
     ),
  );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

bar legend

NOTE

Icon and text customization

The icons color and text of the legend is applied based on the TreemapLevel.color and TreemapLevel.groupMapper properties respectively by default. It is possible to customize the legend icons color and texts using the TreemapColorMapper.color based on the TreemapColorMapper.value or TreemapColorMapper.from and TreemapColorMapper.to properties. You can also customize the legend item’s text using the TreemapColorMapper.name when setting the TreemapColorMapper.range color mapper constructor.

late List<SocialMediaUsers> _source;
late List<TreemapColorMapper> _colorMappers;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];

   _colorMappers = <TreemapColorMapper>[
      TreemapColorMapper.range(from: 0, to: 10, color: Colors.blue[200]!),
      TreemapColorMapper.range(from: 10, to: 20, color: Colors.deepOrange),
      TreemapColorMapper.range(from: 20, to: 30, color: Colors.blue[800]!),
    ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
            colorValueMapper: (TreemapTile tile) {
              return tile.weight;
            },
          ),
        ],
        colorMappers: _colorMappers,
        legend: TreemapLegend.bar(),
     ),
  );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

legend icon color

First segment label customization

You can customize the first segment label of the legend using the TreemapColorMapper.name 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 TreemapColorMapper.from value is placed at the starting position of first segment and the TreemapColorMapper.to value is placed at the ending position of the first segment.

late List<SocialMediaUsers> _source;
late List<TreemapColorMapper> _colorMappers;

@override
void initState() {
  _source = <SocialMediaUsers>[
    SocialMediaUsers('India', 'Facebook', 25.4),
    SocialMediaUsers('USA', 'Instagram', 19.11),
    SocialMediaUsers('Japan', 'Facebook', 13.3),
    SocialMediaUsers('Germany', 'Instagram', 10.65),
    SocialMediaUsers('France', 'Twitter', 7.54),
    SocialMediaUsers('UK', 'Instagram', 4.93),
  ];

  _colorMappers = <TreemapColorMapper>[
    TreemapColorMapper.range(
        from: 0, to: 10, color: Colors.blue[200]!, name: '{0M},{10M}'),
    TreemapColorMapper.range(
        from: 10, to: 20, color: Colors.deepOrange, name: '20M'),
    TreemapColorMapper.range(
        from: 20, to: 30, color: Colors.blue[800]!, name: '30M'),
  ];
  super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: SfTreemap(
      dataCount: _source.length,
      weightValueMapper: (int index) {
        return _source[index].usersInMillions;
      },
      levels: [
        TreemapLevel(
          padding: const EdgeInsets.all(1.5),
          groupMapper: (int index) {
            return _source[index].country;
          },
          colorValueMapper: (TreemapTile tile) {
            return tile.weight;
          },
        ),
      ],
      colorMappers: _colorMappers,
      legend: TreemapLegend.bar(),
    ),
  );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

First label customization

Position

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

late List<SocialMediaUsers> _source;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(2.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
          ),
        ],
        legend: TreemapLegend(
          position: TreemapLegendPosition.bottom,
        ),
     ),
  );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

legend position

NOTE

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

Offset

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

If the property TreemapLegend.offset has been set with the property TreemapLegend.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<SocialMediaUsers> _source;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
          ),
        ],
        legend: TreemapLegend(
          offset: Offset(70, 250),
        ),
     ),
  );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

Overflow mode

For default legend

You can wrap or scroll the legend items using the TreemapLegend.overflowMode property. The default value of the overflowMode property is TreemapLegendOverflowMode.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<SocialMediaUsers> _source;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('China', 'Facebook', 12.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('South America', 'Twitter', 5.54),
      SocialMediaUsers('United Kingdom', 'Instagram', 4.93),
   ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
          ),
        ],
        legend: TreemapLegend(
          overflowMode: TreemapLegendOverflowMode.scroll,
        ),
      ),
   );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

default legend overflow mode

For bar legend

You can wrap or scroll the bar legend items using the TreemapLegend.overflowMode property. The default value of the overflowMode property is TreemapLegendOverflowMode.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<SocialMediaUsers> _source;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];
   super.initState();
}

@override
Widget build(BuildContext context) {
   return Scaffold(
      body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
          ),
        ],
        legend: TreemapLegend.bar(
          overflowMode: TreemapLegendOverflowMode.scroll,
        ),
      ),
   );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

bar legend overflow mode

NOTE

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

Text style

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

late List<SocialMediaUsers> _source;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
          ),
        ],
        legend: TreemapLegend(
          textStyle: TextStyle(
            color: Colors.red,
            fontSize: 14,
            fontWeight: FontWeight.bold,
            fontStyle: FontStyle.italic,
          ),
        ),
      ),
   );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

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 TreemapIconType.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(8.0, 8.0).
  • 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<SocialMediaUsers> _source;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
          ),
        ],
        legend: TreemapLegend(
          iconType: TreemapIconType.triangle,
          iconSize: Size(12.0, 12.0),
          spacing: 15,
          padding: EdgeInsets.all(12.0),
          direction: Axis.vertical,
        ),
      ),
   );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

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 TreemapLegendPaintingStyle.solid. By defaults TreemapLegendPaintingStyle will be solid.

late List<SocialMediaUsers> _source;
late List<TreemapColorMapper> _colorMappers;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];

   _colorMappers = <TreemapColorMapper>[
      TreemapColorMapper.range(from: 0, to: 10, color: Colors.blue[200]!),
      TreemapColorMapper.range(from: 10, to: 20, color: Colors.deepOrange),
      TreemapColorMapper.range(from: 20, to: 30, color: Colors.blue[800]!),
    ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
            colorValueMapper: (TreemapTile tile) {
              return tile.weight;
            },
          ),
        ],
        colorMappers: _colorMappers,
        legend: TreemapLegend.bar(
          segmentPaintingStyle: TreemapLegendPaintingStyle.solid,
        ),
      ),
   );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

Bar legend solid type

Gradient

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

late List<SocialMediaUsers> _source;
late List<TreemapColorMapper> _colorMappers;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];

   _colorMappers = <TreemapColorMapper>[
      TreemapColorMapper.range(from: 0, to: 10, color: Colors.blue[200]!),
      TreemapColorMapper.range(from: 10, to: 20, color: Colors.deepOrange),
      TreemapColorMapper.range(from: 20, to: 30, color: Colors.blue[800]!),
    ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
            colorValueMapper: (TreemapTile tile) {
              return tile.weight;
            },
          ),
        ],
        colorMappers: _colorMappers,
        legend: TreemapLegend.bar(
          segmentPaintingStyle: TreemapLegendPaintingStyle.solid,
        ),
      ),
   );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

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. The default value of the segmentSize property is Size(80.0, 12.0).
  • 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 TreemapLabelOverflow.visible.
  • 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 TreemapLegendEdgeLabelsPlacement.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<SocialMediaUsers> _source;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('United Kingdom', 'Instagram', 4.93),
      SocialMediaUsers('France', 'Twitter', 7.54),
   ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
          ),
        ],
        legend: TreemapLegend.bar(
          segmentSize: Size(60, 12),
          labelOverflow: TreemapLabelOverflow.ellipsis,
          edgeLabelsPlacement: TreemapLegendEdgeLabelsPlacement.center,
          padding: EdgeInsets.all(12),
          direction: Axis.horizontal,
          spacing: 5,
        ),
      ),
   );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

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 TreemapColorMapper.name property. The TreemapColorMapper.from value of the first item is positioned at starting point of the first segment and the TreemapColorMapper.to value of the first item is placed at the first segment end position. For other segments, the values of TreemapColorMapper.to is positioned as label between the other segments.

late List<SocialMediaUsers> _source;
late List<TreemapColorMapper> _colorMappers;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];

   _colorMappers = <TreemapColorMapper>[
      TreemapColorMapper.range(from: 0, to: 10, color: Colors.blue[200]!),
      TreemapColorMapper.range(from: 10, to: 20, color: Colors.deepOrange),
      TreemapColorMapper.range(from: 20, to: 30, color: Colors.blue[800]!),
    ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
            colorValueMapper: (TreemapTile tile) {
              return tile.weight;
            },
          ),
        ],
        colorMappers: _colorMappers,
        legend: TreemapLegend.bar(
          labelsPlacement: TreemapLegendLabelsPlacement.betweenItems,
          segmentPaintingStyle: TreemapLegendPaintingStyle.gradient,
        ),
      ),
   );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

Bar legend labels placement

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

late List<SocialMediaUsers> _source;
late List<TreemapColorMapper> _colorMappers;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];

   _colorMappers = <TreemapColorMapper>[
      TreemapColorMapper.range(
          from: 0, to: 10, color: Colors.blue[200]!, name: '<10'),
      TreemapColorMapper.range(
          from: 10, to: 20, color: Colors.deepOrange, name: '10 - 20'),
      TreemapColorMapper.range(
          from: 20, to: 30, color: Colors.blue[800]!, name: '20 - 30'),
    ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
            colorValueMapper: (TreemapTile tile) {
              return tile.weight;
            },
          ),
        ],
        colorMappers: _colorMappers,
        legend: TreemapLegend.bar(
          labelsPlacement: TreemapLegendLabelsPlacement.betweenItems,
          segmentPaintingStyle: TreemapLegendPaintingStyle.gradient,
        ),
      ),
   );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

Bar legend labels placement

The labels are positioned at the center of the segments when setting the labelsPlacement property to TreemapLegendLabelsPlacement.onItem. The labels will based on the value of TreemapColorMapper.name property. If the value of TreemapColorMapper.name property is null, labels will be based on the values of TreemapColorMapper.from and TreemapColorMapper.to properties.

late List<SocialMediaUsers> _source;
late List<TreemapColorMapper> _colorMappers;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];

   _colorMappers = <TreemapColorMapper>[
      TreemapColorMapper.range(
          from: 0, to: 10, color: Colors.blue[200]!, name: '<10'),
      TreemapColorMapper.range(
          from: 10, to: 20, color: Colors.deepOrange, name: '10 - 20'),
      TreemapColorMapper.range(
          from: 20, to: 30, color: Colors.blue[800]!, name: '20 - 30'),
    ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(1.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
            colorValueMapper: (TreemapTile tile) {
              return tile.weight;
            },
          ),
        ],
        colorMappers: _colorMappers,
        legend: TreemapLegend.bar(
          labelsPlacement: TreemapLegendLabelsPlacement.onItem,
          edgeLabelsPlacement: TreemapLegendEdgeLabelsPlacement.center,
          segmentPaintingStyle: TreemapLegendPaintingStyle.gradient,
        ),
      ),
   );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

Bar legend labels placement

Labels placement for equal color mapper

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

late List<SocialMediaUsers> _source;
late List<TreemapColorMapper> _colorMappers;

@override
void initState() {
   _source = <SocialMediaUsers>[
      SocialMediaUsers('India', 'Facebook', 25.4),
      SocialMediaUsers('USA', 'Instagram', 19.11),
      SocialMediaUsers('Japan', 'Facebook', 13.3),
      SocialMediaUsers('Germany', 'Instagram', 10.65),
      SocialMediaUsers('France', 'Twitter', 7.54),
      SocialMediaUsers('UK', 'Instagram', 4.93),
   ];

   _colorMappers = <TreemapColorMapper>[
      TreemapColorMapper.value(value: 'Facebook', color: Colors.blue[200]!),
      TreemapColorMapper.value(value: 'Instagram', color: Colors.deepOrange),
      TreemapColorMapper.value(value: 'Twitter', color: Colors.blue[800]!),
    ];
   super.initState();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfTreemap(
        dataCount: _source.length,
        weightValueMapper: (int index) {
          return _source[index].usersInMillions;
        },
        levels: [
          TreemapLevel(
            padding: const EdgeInsets.all(2.5),
            groupMapper: (int index) {
              return _source[index].country;
            },
            labelBuilder: (BuildContext context, TreemapTile tile) {
              return Text(_source[tile.indices[0]].socialMedia);
            },
            colorValueMapper: (TreemapTile tile) {
              return _source[tile.indices[0]].socialMedia;
            },
          ),
        ],
        colorMappers: _colorMappers,
        legend: TreemapLegend.bar(
          edgeLabelsPlacement: TreemapLegendEdgeLabelsPlacement.center,
          segmentPaintingStyle: TreemapLegendPaintingStyle.gradient,
        ),
      ),
   );
}

class SocialMediaUsers {
  const SocialMediaUsers(this.country, this.socialMedia, this.usersInMillions);

  final String country;
  final String socialMedia;
  final double usersInMillions;
}

Bar legend labels placement