Javafx 简明教程

JavaFX - Area Chart

面积图用于绘制基于面积的图表。它绘制给定序列点和轴之间的面积。通常，此图表用于比较两个数量。

Area charts are used to draw area based charts. It plots the area between the given series of points and the axis. In general, this chart is used to compare two quantities.

以下是面积图，描述了两个人一周内消耗的水果数量。

Following is an Area chart depicting the number of fruits consumed by two people in a week.

Area Chart in JavaFX

在 JavaFX 中，区域图由一个名为 AreaChart 的类表示。该类属于 javafx.scene.chart 包。通过实例化此类，可以在 JavaFX 中创建一个 AreaChart 节点。

In JavaFX, an Area chart is represented by a class named AreaChart. This class belongs to the package javafx.scene.chart. By instantiating this class, you can create an AreaChart node in JavaFX.

要生成 JavaFX 中的面积图，请按照以下步骤操作。

To generate an area chart in JavaFX, follow the steps given below.

Step 1: Defining the Axis

定义区域图的 X 和 Y 轴，并为它们设置标签。在我们的示例中，X 轴表示一周中的天数，y 轴表示消耗的水果单位。

Define the X and Y axis of the area chart and set labels to them. In our example, X axis represents the days in a week and the y axis represents the units of fruits consumed.

public class ClassName extends Application {
   @Override
   public void start(Stage primaryStage) throws Exception {
      //Defining the X axis
      CategoryAxis xAxis = new CategoryAxis();

      //Defining the y Axis
      NumberAxis yAxis = new NumberAxis(0, 15, 2.5);
      yAxis.setLabel("Fruit units");
   }
}

Step 2: Creating the Area Chart

通过实例化 javafx.scene.chart 包中的名为 AreaChart 的类来创建一个折线图。向此类的构造函数传递在上一步骤中创建的表示 X 和 Y 轴的对象。

Create a line chart by instantiating the class named AreaChart of the package javafx.scene.chart. To the constructor of this class, pass the objects representing the X and Y axis created in the previous step.

//Creating the Area chart
AreaChart<String, Number> areaChart = new AreaChart(xAxis, yAxis);
areaChart.setTitle("Average fruit consumption during one week");

Step 3: Preparing the data

实例化 XYChart.Series 类。然后将数据（一系列 x 和 y 坐标）添加到此类的 Observable 列表中，如下所示 −

Instantiate the XYChart.Series class. Then add the data (a series of, x and y coordinates) to the Observable list of this class as follows −

//Prepare XYChart.Series objects by setting data
XYChart.Series series1 = new XYChart.Series();
series1.setName("John");
series1.getData().add(new XYChart.Data("Monday", 3));
series1.getData().add(new XYChart.Data("Tuesday", 4));
series1.getData().add(new XYChart.Data("Wednesday", 3));
series1.getData().add(new XYChart.Data("Thursday", 5));
series1.getData().add(new XYChart.Data("Friday", 4));
series1.getData().add(new XYChart.Data("Saturday", 10));
series1.getData().add(new XYChart.Data("Sunday", 12));

XYChart.Series series2 = new XYChart.Series();
series2.setName("Jane");
series2.getData().add(new XYChart.Data("Monday", 1));
series2.getData().add(new XYChart.Data("Tuesday", 3));
series2.getData().add(new XYChart.Data("Wednesday", 4));

series2.getData().add(new XYChart.Data("Thursday", 3));
series2.getData().add(new XYChart.Data("Friday", 3));
series2.getData().add(new XYChart.Data("Saturday", 5));
series2.getData().add(new XYChart.Data("Sunday", 4));

Step 4: Add Data to the Area Chart

将上一步骤中准备好的数据序列添加到折线图，如下所示：

Add the data series prepared in the previous step to the area chart as follows −

//Setting the XYChart.Series objects to area chart
areaChart.getData().addAll(series1,series2);

Step 5: Creating a Group Object

在 start() 方法中，通过实例化名为 Group 、属于包 javafx.scene 的类来创建组对象。

In the start() method, create a group object by instantiating the class named Group, which belongs to the package javafx.scene.

将上一步骤中创建的 AreaChart（节点）对象作一个参数传递给 Group 类的构造函数。应当这样做才能像如下所示将其添加到组中 −

Pass the AreaChart (node) object, created in the previous step as a parameter to the constructor of the Group class. This should be done in order to add it to the group as follows −

Group root = new Group(areaChart);

Step 6: Launching Application

最后，按照下面给出的步骤正确启动应用程序 −

Lastly, follow the given steps below to launch the application properly −

Firstly, instantiate the class named Scene by passing the Group object as a parameter value to its constructor. To this constructor, you can also pass dimensions of the application screen as optional parameters.
Then, set the title to the stage using the setTitle() method of the Stage class.
Now, a Scene object is added to the stage using the setScene() method of the class named Stage.
Display the contents of the scene using the method named show().
Lastly, the application is launched with the help of the launch() method.

Example

下表描绘了 John 和 Jane 在一周内食用的水果数量。

The following table depicts the number of fruits consumed by John and Jane in a week.

Day of the Week	Fruits consumed by John	Fruits consumed by Jane
Monday	3	1
Tuesday	4	3
Wednesday	3	4
Thursday	5	3
Friday	4	3
Saturday	10	5
Sunday	12	4

以下是一个 Java 程序，它使用 JavaFX 生成区域图，描绘以上数据。

Following is a Java program which generates an area chart, depicting the above data using JavaFX.

将此代码保存在名为 AreaChartExample.java 的文件中。

Save this code in a file with the name AreaChartExample.java.

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.chart.AreaChart;
import javafx.scene.chart.CategoryAxis;
import javafx.stage.Stage;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;

public class AreaChartExample extends Application {
   @Override
   public void start(Stage stage) {
      //Defining the X axis
      CategoryAxis xAxis = new CategoryAxis();

      //defining the y Axis
      NumberAxis yAxis = new NumberAxis(0, 15, 2.5);
      yAxis.setLabel("Fruit units");

      //Creating the Area chart
      AreaChart<String, Number> areaChart = new AreaChart(xAxis, yAxis);
      areaChart.setTitle("Average fruit consumption during one week");

      //Prepare XYChart.Series objects by setting data
      XYChart.Series series1 = new XYChart.Series();
      series1.setName("John");
      series1.getData().add(new XYChart.Data("Monday", 3));
      series1.getData().add(new XYChart.Data("Tuesday", 4));
      series1.getData().add(new XYChart.Data("Wednesday", 3));
      series1.getData().add(new XYChart.Data("Thursday", 5));
      series1.getData().add(new XYChart.Data("Friday", 4));
      series1.getData().add(new XYChart.Data("Saturday", 10));
      series1.getData().add(new XYChart.Data("Sunday", 12));

      XYChart.Series series2 = new XYChart.Series();
      series2.setName("Jane");
      series2.getData().add(new XYChart.Data("Monday", 1));
      series2.getData().add(new XYChart.Data("Tuesday", 3));
      series2.getData().add(new XYChart.Data("Wednesday", 4));
      series2.getData().add(new XYChart.Data("Thursday", 3));
      series2.getData().add(new XYChart.Data("Friday", 3));
      series2.getData().add(new XYChart.Data("Saturday", 5));
      series2.getData().add(new XYChart.Data("Sunday", 4));

      //Setting the XYChart.Series objects to area chart
      areaChart.getData().addAll(series1,series2);

      //Creating a Group object
      Group root = new Group(areaChart);

      //Creating a scene object
      Scene scene = new Scene(root, 600, 400);

      //Setting title to the Stage
      stage.setTitle("Area Chart");

      //Adding scene to the stage
      stage.setScene(scene);

      //Displaying the contents of the stage
      stage.show();
   }
   public static void main(String args[]){
      launch(args);
   }
}

使用以下命令，从命令提示符编译并执行已保存的 java 文件。

Compile and execute the saved java file from the command prompt using the following commands.

javac --module-path %PATH_TO_FX% --add-modules javafx.controls AreaChartExample.java
java --module-path %PATH_TO_FX% --add-modules javafx.controls AreaChartExample

执行后，上述程序会生成一个 JavaFX 窗口，显示如下所示的区域图。

On executing, the above program generates a JavaFX window displaying an area chart as shown below.

Example

我们再看另一个示例，在其中尝试通过 2017 年 - 2022 年来描绘两个不同城市的人口增长情况。

Let us see another example where we are trying to depict the population increase in two different cities through the years 2017 - 2022.

Years	Population in City A	Population in City B
2017	3000	1678
2018	4573	2374
2019	5753	4124
2020	6476	5963
2021	7340	7570
2022	8301	8500

将此代码保存在名为 AreaChartPopulation.java 的文件中。

Save this code in a file with the name AreaChartPopulation.java.

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.chart.AreaChart;
import javafx.scene.chart.CategoryAxis;
import javafx.stage.Stage;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;

public class AreaChartPopulation extends Application {
   @Override
   public void start(Stage stage) {
      //Defining the X axis
      NumberAxis xAxis = new NumberAxis(2017, 2022, 1);
      xAxis.setLabel("Years");

      //defining the y Axis
      NumberAxis yAxis = new NumberAxis();
      yAxis.setLabel("Population");

      //Creating the Area chart
      AreaChart<String, Number> areaChart = new AreaChart(xAxis, yAxis);
      areaChart.setTitle("Population in Two Cities Over Years");

      //Prepare XYChart.Series objects by setting data
      XYChart.Series series1 = new XYChart.Series();
      series1.setName("City A");
      series1.getData().add(new XYChart.Data(2017, 3000));
      series1.getData().add(new XYChart.Data(2018, 4573));
      series1.getData().add(new XYChart.Data(2019, 5753));
      series1.getData().add(new XYChart.Data(2020, 6476));
      series1.getData().add(new XYChart.Data(2021, 7340));
      series1.getData().add(new XYChart.Data(2022, 8301));

      XYChart.Series series2 = new XYChart.Series();
      series2.setName("City B");
      series2.getData().add(new XYChart.Data(2017, 1678));
      series2.getData().add(new XYChart.Data(2018, 2374));
      series2.getData().add(new XYChart.Data(2019, 4124));
      series2.getData().add(new XYChart.Data(2020, 5963));
      series2.getData().add(new XYChart.Data(2021, 7570));
      series2.getData().add(new XYChart.Data(2022, 8500));

      //Setting the XYChart.Series objects to area chart
      areaChart.getData().addAll(series1,series2);

      //Creating a Group object
      Group root = new Group(areaChart);

      //Creating a scene object
      Scene scene = new Scene(root, 600, 400);

      //Setting title to the Stage
      stage.setTitle("Area Chart");

      //Adding scene to the stage
      stage.setScene(scene);

      //Displaying the contents of the stage
      stage.show();
   }
   public static void main(String args[]){
      launch(args);
   }
}

使用以下命令，从命令提示符编译并执行已保存的 java 文件。

Compile and execute the saved java file from the command prompt using the following commands.

javac --module-path %PATH_TO_FX% --add-modules javafx.controls AreaChartPopulation.java
java --module-path %PATH_TO_FX% --add-modules javafx.controls AreaChartPopulation

执行后，上述程序会生成一个 JavaFX 窗口，显示如下所示的区域图。

On executing, the above program generates a JavaFX window displaying an area chart as shown below.