2019独角兽企业重金招聘Python工程师标准>>> 
3、代码如下：
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),
),
);
}
}