flutter 数据可视化——饼图

1、pubspec文件管理Flutter应用程序的assets(资源，如图片、package等)。 在pubspec.yaml中，通过网址“https://pub.dartlang.org/packages/charts_flutter”确认版本号后，将charts_flutter（0.5.0或更高版本）添加到依赖项列表。

2、在Android Studio的编辑器视图中查看pubspec时，单击右上角的 Packages get，或者在命令行输入“flutter packages get”；这会将依赖包安装到您的项目。

3、运行以下代码

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

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class ClicksPerYear {
  final String year;
  final int clicks;
  final charts.Color color;

  ClicksPerYear(this.year, this.clicks, Color color)
      : this.color = new charts.Color(
      r: color.red, g: color.green, b: color.blue, a: color.alpha);
}

class _MyHomePageState extends State {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    var data = [
      new ClicksPerYear('2016', 12, Colors.red),
      new ClicksPerYear('2017', 42, Colors.yellow),
      new ClicksPerYear('2018', _counter, Colors.green),
    ];

    var series = [
      new charts.Series(
        domainFn: (ClicksPerYear clickData, _) => clickData.year,
        measureFn: (ClicksPerYear clickData, _) => clickData.clicks,
        colorFn: (ClicksPerYear clickData, _) => clickData.color,
        id: 'Clicks',
        data: data,
      ),
    ];
    var chart = new charts.BarChart(
      series,
      animate: true,
    );
    var chartWidget = new Padding(
      padding: new EdgeInsets.all(32.0),
      child: new SizedBox(
        height: 200.0,
        child: chart,
      ),
    );

    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            new Text(
              'You have pushed the button this many times:',
            ),
            new Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
            chartWidget,
          ],
        ),
      ),
      floatingActionButton: new FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: new Icon(Icons.add),
      ),
    );
  }
}