charts_flutter:折线图中负值的不同颜色

dependencies:
  charts_flutter: ^0.10.0

import 'package:charts_flutter/flutter.dart' as charts;

import 'package:flutter/material.dart';
import 'package:charts_flutter/flutter.dart' as charts;

class LineChartWithNegativeColor extends StatelessWidget {
  final List<charts.Series> seriesList;
  final bool animate;

  LineChartWithNegativeColor(this.seriesList, {this.animate});

  @override
  Widget build(BuildContext context) {
    return charts.LineChart(
      seriesList,
      animate: animate,
      defaultRenderer: charts.LineRendererConfig(
        includeArea: true,
        includePoints: true,
        includeLine: true,
        stacked: false,
        customRendererId: 'customRenderer',
      ),
      customSeriesRenderers: [
        charts.LineRendererConfig(
          customRendererId: 'customRenderer',
          includeArea: true,
          includePoints: true,
          includeLine: true,
          stacked: false,
          areaColorFn: (datum, index) {
            if (datum.y < 0) {
              return charts.MaterialPalette.red.shadeDefault;
            } else {
              return charts.MaterialPalette.blue.shadeDefault;
            }
          },
        ),
      ],
    );
  }
}

void main() {
  runApp(
    MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Line Chart with Negative Color'),
        ),
        body: Padding(
          padding: EdgeInsets.all(8.0),
          child: LineChartWithNegativeColor(
            _createSampleData(),
            animate: true,
          ),
        ),
      ),
    ),
  );
}

List<charts.Series<LinearSales, int>> _createSampleData() {
  final data = [
    LinearSales(0, 5),
    LinearSales(1, -10),
    LinearSales(2, 15),
    LinearSales(3, -20),
    LinearSales(4, 25),
  ];

  return [
    charts.Series<LinearSales, int>(
      id: 'Sales',
      colorFn: (_, __) => charts.MaterialPalette.blue.shadeDefault,
      domainFn: (LinearSales sales, _) => sales.year,
      measureFn: (LinearSales sales, _) => sales.sales,
      data: data,
    )
  ];
}

class LinearSales {
  final int year;
  final int sales;

  LinearSales(this.year, this.sales);
}