【Flutter】タッチするとギミックが表示される円グラフの使い方

dependencies:
  fl_chart: ^0.40.0

import 'package:fl_chart/fl_chart.dart';
import 'package:flutter/material.dart';
import 'indicator.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: PieChartSample2(),
    );
  }
}

class PieChartSample2 extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => PieChart2State();
}

class PieChart2State extends State {
  int touchedIndex = -1;

  @override
  Widget build(BuildContext context) {
    return AspectRatio(
      aspectRatio: 1.3,
      child: Card(
        color: Colors.white,
        child: Row(
          children: <Widget>[
            const SizedBox(
              height: 18,
            ),
            Expanded(
              child: AspectRatio(
                aspectRatio: 1,
                child: PieChart(
                  PieChartData(
                      pieTouchData:
                          PieTouchData(touchCallback: (FlTouchEvent event, pieTouchResponse) {
                        setState(() {
                          if (!event.isInterestedForInteractions ||
                              pieTouchResponse == null ||
                              pieTouchResponse.touchedSection == null) {
                            touchedIndex = -1;
                            return;
                          }
                          touchedIndex = pieTouchResponse.touchedSection!.touchedSectionIndex;
                        });
                      }),
                      borderData: FlBorderData(
                        show: false,
                      ),
                      sectionsSpace: 0,
                      centerSpaceRadius: 40,
                      sections: showingSections()),
                ),
              ),
            ),
            Column(
              mainAxisSize: MainAxisSize.max,
              mainAxisAlignment: MainAxisAlignment.end,
              crossAxisAlignment: CrossAxisAlignment.start,
              children: const <Widget>[
                Indicator(
                  color: Color(0xff0293ee),
                  text: 'First',
                  isSquare: true,
                ),
                SizedBox(
                  height: 4,
                ),
                Indicator(
                  color: Color(0xfff8b250),
                  text: 'Second',
                  isSquare: true,
                ),
                SizedBox(
                  height: 4,
                ),
                Indicator(
                  color: Color(0xff845bef),
                  text: 'Third',
                  isSquare: true,
                ),
                SizedBox(
                  height: 4,
                ),
                Indicator(
                  color: Color(0xff13d38e),
                  text: 'Fourth',
                  isSquare: true,
                ),
                SizedBox(
                  height: 18,
                ),
              ],
            ),
            const SizedBox(
              width: 28,
            ),
          ],
        ),
      ),
    );
  }

  List<PieChartSectionData> showingSections() {
    return List.generate(4, (i) {
      final isTouched = i == touchedIndex;
      final fontSize = isTouched ? 25.0 : 16.0;
      final radius = isTouched ? 60.0 : 50.0;
      switch (i) {
        case 0:
          return PieChartSectionData(
            color: const Color(0xff0293ee),
            value: 40,
            title: '40%',
            radius: radius,
            titleStyle: TextStyle(
                fontSize: fontSize, fontWeight: FontWeight.bold, color: const Color(0xffffffff)),
          );
        case 1:
          return PieChartSectionData(
            color: const Color(0xfff8b250),
            value: 30,
            title: '30%',
            radius: radius,
            titleStyle: TextStyle(
                fontSize: fontSize, fontWeight: FontWeight.bold, color: const Color(0xffffffff)),
          );
        case 2:
          return PieChartSectionData(
            color: const Color(0xff845bef),
            value: 15,
            title: '15%',
            radius: radius,
            titleStyle: TextStyle(
                fontSize: fontSize, fontWeight: FontWeight.bold, color: const Color(0xffffffff)),
          );
        case 3:
          return PieChartSectionData(
            color: const Color(0xff13d38e),
            value: 15,
            title: '15%',
            radius: radius,
            titleStyle: TextStyle(
                fontSize: fontSize, fontWeight: FontWeight.bold, color: const Color(0xffffffff)),
          );
        default:
          throw Error();
      }
    });
  }
}

import 'package:flutter/material.dart';

class Indicator extends StatelessWidget {
  final Color color;
  final String text;
  final bool isSquare;
  final double size;
  final Color textColor;

  const Indicator({
    Key? key,
    required this.color,
    required this.text,
    required this.isSquare,
    this.size = 16,
    this.textColor = const Color(0xff505050),
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Row(
      children: <Widget>[
        Container(
          width: size,
          height: size,
          decoration: BoxDecoration(
            shape: isSquare ? BoxShape.rectangle : BoxShape.circle,
            color: color,
          ),
        ),
        const SizedBox(
          width: 4,
        ),
        Text(
          text,
          style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold, color: textColor),
        )
      ],
    );
  }
}