flutter_circular_chart/example/animated_radial_chart_example.dart

import 'package:flutter/material.dart';
import 'package:flutter_circular_chart/flutter_circular_chart.dart';

void main() {
  runApp(new MaterialApp(
    home: new AnimatedRadialChartExample(),
  ));
}

class AnimatedRadialChartExample extends StatefulWidget {
  @override
  _AnimatedRadialChartExampleState createState() =>
      new _AnimatedRadialChartExampleState();
}

class _AnimatedRadialChartExampleState
    extends State<AnimatedRadialChartExample> {
  final GlobalKey<AnimatedCircularChartState> _chartKey =
      new GlobalKey<AnimatedCircularChartState>();
  final _chartSize = const Size(200.0, 200.0);

  double value = 50.0;

  void _increment() {
    setState(() {
      value += 10;
      List<CircularStackEntry> data = _generateChartData(value);
      _chartKey.currentState.updateData(data);
    });
  }

  void _decrement() {
    setState(() {
      value -= 10;
      List<CircularStackEntry> data = _generateChartData(value);
      _chartKey.currentState.updateData(data);
    });
  }

  List<CircularStackEntry> _generateChartData(double value) {
    Color dialColor = Colors.blue[200];
    if (value < 0) {
      dialColor = Colors.red[200];
    } else if (value < 50) {
      dialColor = Colors.yellow[200];
    }

    List<CircularStackEntry> data = <CircularStackEntry>[
      new CircularStackEntry(
        <CircularSegmentEntry>[
          new CircularSegmentEntry(
            value,
            dialColor,
            rankKey: 'percentage',
          )
        ],
        rankKey: 'percentage',
      ),
    ];

    if (value > 100) {
      data.add(new CircularStackEntry(
        <CircularSegmentEntry>[
          new CircularSegmentEntry(
            value - 100,
            Colors.green[200],
            rankKey: 'percentage',
          ),
        ],
        rankKey: 'percentage2',
      ));
    }

    return data;
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: const Text('Percentage Dial'),
      ),
      body: new Column(
        children: <Widget>[
          new Container(
            child: new AnimatedCircularChart(
              key: _chartKey,
              size: _chartSize,
              initialChartData: _generateChartData(value),
              chartType: CircularChartType.Radial,
              percentageValues: true,
            ),
          ),
          new Text(
            '%$value',
            style: Theme.of(context).textTheme.title,
          ),
          new Row(
            mainAxisAlignment: MainAxisAlignment.spaceAround,
            children: <Widget>[
              new RaisedButton(onPressed: _increment, child: const Text('+10')),
              new RaisedButton(onPressed: _decrement, child: const Text('-10')),
            ],
          ),
        ],
      ),
    );
  }
}