How to apply color in treemap widget based on positive and negative values?
In this article, we explain how to apply color in the Flutter Treemap widget based on positive and negative values.
To show the colors based on the positive and negative values, the colorValueMapper property can be used in the SfTreemap widget.
Step 1: Initialize the treemapData variable which holds the data source for the treemap. Here the data consists of car model name, sales count of the cars in a year, and increased or decreased percentage of sales.
late List<TreemapData> treemapData;
@override
void initState() {
treemapData = const <TreemapData>[
TreemapData(model: 'Ertiga+XL6', sales: 104190, percentage: -10),
TreemapData(model: 'Eeco', sales: 99480, percentage: 10),
TreemapData(model: 'Fortuner', sales: 9204, percentage: 18),
TreemapData(model: 'Glanza', sales: 20676, percentage: 27),
TreemapData(model: 'Scorpio', sales: 31240, percentage: -40),
TreemapData(model: 'XUV 500', sales: 7053, percentage: -70),
];
super.initState();
}
class TreemapData {
const TreemapData(
{required this.model, required this.sales, required this.percentage });
final String model;
final double sales;
final double percentage;
}
Step 2: Create the SfTreemap widget, assign the treemapData list’s length to dataCount, map the sales value to weightValueMapper. Then initialize the required properties. Then assign the color based on the positive and negative values using the colorValueMapper property as in below code.
@override
Widget build(BuildContext context) {
return SfTreemap(
dataCount: treemapData.length,
weightValueMapper: (int index) => treemapData[index].sales,
levels: <TreemapLevel>[
TreemapLevel(
groupMapper: (int index) => treemapData[index].model,
colorValueMapper: (TreemapTile tile) {
final double percentage = treemapData[tile.indices[0]].percentage;
if (percentage > 0) {
return Colors.red;
} else {
return Colors.green;
}
},
labelBuilder: (BuildContext context, TreemapTile tile) {
return Padding(
padding: const EdgeInsets.all(4.0),
child: Text(tile.group, overflow: TextOverflow.ellipsis),
);
},
),
],
);
}
Now the treemap will render with red color for the negative values and green color for the positive values.
Conclusion
I hope you enjoyed learning about how to apply color in treemap widget based on positive and negative values.
You can refer to our Flutter Treemap feature tour page to know about its other groundbreaking feature representations. You can also explore our Flutter Treemap documentation to understand how to create and manipulate data.
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