flutter条形码_Flutter：使用Charts_flutter创建条形图

痛定思痛。 2022-11-27 04:28 326阅读 0赞

flutter条形码

Bar charts are useful ways to display data to a user, and with the use of the `charts_flutter` charting library, it’s easier than ever!

条形图是向用户显示数据的有用方法，并且通过使用`charts_flutter`图表库，它比以往任何时候都更容易！

This article will see us mapping World of Warcraft subscriber numbers between the years of 2008-2015.

本文将使我们了解到2008-2015年间的《魔兽世界》用户数量。

## 创建一个新的Flutter项目 **(**Creating a New Flutter Project**)** ##

As always, we’ll start off by setting up a new project and adding the `charts_flutter` plugin:

与往常一样，我们将从建立一个新项目并添加`charts_flutter`插件开始：

# New Flutter project
    $ flutter create bar_wow
    
    # Open this up inside of VS Code
    $ cd bar_wow && code .

## 添加Charts\_flutter插件 **(**Adding the charts\_flutter plugin**)** ##

Next up, we’ll need to add the `charts_flutter` plugin within our `pubspec.yaml`:

接下来，我们需要添加`charts_flutter`我们中的插件`pubspec.yaml` ：

dependencies:
      flutter:
        sdk: flutter
    
      charts_flutter: ^0.8.1

We can now go ahead and run this on the iOS or Android simulator/device of your choice.

现在，我们可以继续在您选择的iOS或Android模拟器/设备上运行此程序。

## 脚手架的应用 **(**Scaffolding Our Application**)** ##

Let’s replace everything inside of `main.dart` with a `MaterialApp` that points at a `HomePage` which can be found at `home.dart`:

让我们用一个指向`HomePage`的`MaterialApp`替换`main.dart`内部的所有内容，该`HomePage`可以在`home.dart`找到：

main.dart

import 'package:bar_wow/home.dart';
    import 'package:flutter/material.dart';
    
    void main() => runApp(MyApp());
    
    class MyApp extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return MaterialApp(
          debugShowCheckedModeBanner: false,
          home: HomePage(),
        );
      }
    }

Next up, we’ll need to create the `HomePage`:

接下来，我们需要创建`HomePage` ：

import 'package:flutter/material.dart';
    
    class HomePage extends StatelessWidget {
    
      @override
      Widget build(BuildContext context) {
        return Scaffold(
          appBar: AppBar(
            backgroundColor: Colors.red,
            title: Text("World of Warcraft Subscribers"),
          ),
          body: Center(
              child: Text("Hello, Charts!"),
            ),
        );
      }
    }

Now that we’ve established a base application, we can go ahead and create the model for our bar chart data.

现在，我们已经建立了基本应用程序，我们可以继续为条形图数据创建模型。

## 订户模型 **(**Subscriber Model**)** ##

Our bar chart will be focused on showing the amount of World of Warcraft subscribers for a particular year, therefore, our model would look something like this:

我们的条形图将专注于显示特定年份的《魔兽世界》用户数量，因此，我们的模型将如下所示：

subscriber\_series.dart

subscription\_series.dart

import 'package:charts_flutter/flutter.dart' as charts;
    import 'package:flutter/foundation.dart';
    
    class SubscriberSeries {
      final String year;
      final int subscribers;
      final charts.Color barColor;
    
      SubscriberSeries(
          {@required this.year,
          @required this.subscribers,
          @required this.barColor});
    }

This allows us to represent our data in the most simplistic form.

这使我们能够以最简单的形式表示数据。

## 创建数据 **(**Creating the Data**)** ##

For example’s sake, we’re going to be creating the data inside of the `HomePage` as a `List<SubscriberSeries>`:

例如，我们将在`HomePage`中将数据创建为`List<SubscriberSeries>` ：

import 'package:bar_wow/subscriber_chart.dart';
    import 'package:charts_flutter/flutter.dart' as charts;
    import 'package:bar_wow/subscriber_series.dart';
    import 'package:flutter/material.dart';
    
    class HomePage extends StatelessWidget {
      final List<SubscriberSeries> data = [
        SubscriberSeries(
          year: "2008",
          subscribers: 10000000,
          barColor: charts.ColorUtil.fromDartColor(Colors.blue),
        ),
        SubscriberSeries(
          year: "2009",
          subscribers: 11000000,
          barColor: charts.ColorUtil.fromDartColor(Colors.blue),
        ),
        SubscriberSeries(
          year: "2010",
          subscribers: 12000000,
          barColor: charts.ColorUtil.fromDartColor(Colors.blue),
        ),
        SubscriberSeries(
          year: "2011",
          subscribers: 10000000,
          barColor: charts.ColorUtil.fromDartColor(Colors.blue),
        ),
        SubscriberSeries(
          year: "2012",
          subscribers: 8500000,
          barColor: charts.ColorUtil.fromDartColor(Colors.blue),
        ),
        SubscriberSeries(
          year: "2013",
          subscribers: 7700000,
          barColor: charts.ColorUtil.fromDartColor(Colors.blue),
        ),
        SubscriberSeries(
          year: "2014",
          subscribers: 7600000,
          barColor: charts.ColorUtil.fromDartColor(Colors.blue),
        ),
        SubscriberSeries(
          year: "2015",
          subscribers: 5500000,
          barColor: charts.ColorUtil.fromDartColor(Colors.red),
        ),
      ];
    
      @override
      Widget build(BuildContext context) {
        return Scaffold(
          appBar: AppBar(
            backgroundColor: Colors.red,
            title: Text("World of Warcraft Subscribers"),
          ),
          body: Center(
              child: Text("Hello, Charts!"),
            ),
        );
      }
    }

Now that we’ve got our data, all we need to is create the bar chart!

现在我们有了数据，我们所要做的就是创建条形图！

## 创建条形图 **(**Creating the Bar Chart**)** ##

Inside of `subscriber_chart.dart`, create a new `StatelessWidget` named `SubscriberChart` that takes in the `SubscriberSeries` as a `prop`:

在`subscriber_chart.dart`内部，创建一个名为`SubscriberChart`的新`StatelessWidget` ，它以`SubscriberSeries`作为`prop` ：

subscriber\_chart.dart

subscription\_chart.dart

We can then use this `data` to build our `charts.Series` like so:

然后，我们可以使用这些`data`来构建`charts.Series` 。

@override
    Widget build(BuildContext context) {
      List<charts.Series<SubscriberSeries, String>> series = [
        charts.Series(
          id: "Subscribers",
          data: data,
          domainFn: (SubscriberSeries series, _) => series.year,
          measureFn: (SubscriberSeries series, _) => series.subscribers,
          colorFn: (SubscriberSeries series, _) => series.barColor)
      ];
    }

The `domainFn` and `measureFn` is used to compare the `subscribers` data for that `year`. We’re also using the `colorFn` to potentially pass a `barColor` which we did like so:

该`domainFn`和`measureFn`用来比较`subscribers`数据为 `year` 。 我们还使用`colorFn`潜在地传递了`barColor` ，我们这样做是这样的：

SubscriberSeries(
      year: "2008",
      subscribers: 10000000,
      barColor: charts.ColorUtil.fromDartColor(Colors.blue),
    ),

We may want to make the `barColor` optional with a default of `Colors.blue` (or a color of your choice) in a production application, I’ve opted to make one bar red and the rest blue in this instance.

我们可能希望在生产应用程序中将`barColor`设置为可选，默认设置为`Colors.blue` (或您选择的颜色)，在这种情况下，我选择将一个条形设置为红色，将其余的条形设置为蓝色。

Let’s update the `build` function to return our chart:

让我们更新`build`函数以返回图表：

import 'package:charts_flutter/flutter.dart' as charts;
    import 'package:bar_wow/subscriber_series.dart';
    import 'package:flutter/material.dart';
    
    class SubscriberChart extends StatelessWidget {
      final List<SubscriberSeries> data;
    
      SubscriberChart({@required this.data});
    
      @override
      Widget build(BuildContext context) {
        List<charts.Series<SubscriberSeries, String>> series = [
          charts.Series(
              id: "Subscribers",
              data: data,
              domainFn: (SubscriberSeries series, _) => series.year,
              measureFn: (SubscriberSeries series, _) => series.subscribers,
              colorFn: (SubscriberSeries series, _) => series.barColor)
        ];
    
        return Container(
          height: 400,
          padding: EdgeInsets.all(20),
          child: Card(
            child: Padding(
              padding: const EdgeInsets.all(8.0),
              child: Column(
                children: <Widget>[
                  Text(
                    "World of Warcraft Subscribers by Year",
                    style: Theme.of(context).textTheme.body2,
                  ),
                  Expanded(
                    child: charts.BarChart(series, animate: true),
                  )
                ],
              ),
            ),
          ),
        );
      }
    }

What did we do here? We added some markup to our `charts.BarChart` by surrounding it with a `Card`. The key thing to note is that we’re passing the `series` as a `required` parameter to `charts.BarChart`:

我们在这里做了什么？ 我们通过在`charts.BarChart`周围加上`Card`来添加一些标记。 需要注意的关键是我们将`series`作为`required`参数传递给`charts.BarChart` ：

charts.BarChart(
      series,
      animate: true
    )

## 全部接线！ **(**Wiring it All Up!**)** ##

Finally, head over to `home.dart` and change the `build` to use the `SubscriberChart` like so:

最后，转到`home.dart`并更改`build`以使用`SubscriberChart`如下所示：

@override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(
          backgroundColor: Colors.red,
          title: Text("World of Warcraft Subscribers"),
        ),
        body: Center(
            child: SubscriberChart(
          data: data,
        )),
      );
    }

This gives us the following chart:

这给出了以下图表：

> 翻译自: [https://www.digitalocean.com/community/tutorials/flutter-bar-charts][https_www.digitalocean.com_community_tutorials_flutter-bar-charts]

flutter条形码

[https_www.digitalocean.com_community_tutorials_flutter-bar-charts]: https://www.digitalocean.com/community/tutorials/flutter-bar-charts