Javafx 简明教程

JavaFX - Scatter Chart

散点图是一种图形，它使用绘制在笛卡尔平面中的两个变量的值。它通常用于找出两个变量之间的关系。

A scatterplot is a type of graph which uses values from two variables plotted in a Cartesian plane. It is usually used to find out the relationship between two variables.

以下是按面积和重量绘制的散点图。

Following is a Scatter chart plotted between area and weight.

Scatter Chart in JavaFX

在 JavaFX 中，散点图由名为 ScatterChart 的类表示。此类属于 javafx.scene.chart 包。通过实例化此类，可以在 JavaFX 中创建 ScatterChart 节点。

In JavaFX, a Scatter chart is represented by a class named ScatterChart. This class belongs to the package javafx.scene.chart. By instantiating this class, you can create a ScatterChart 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

在应用程序类的 start() 方法中定义面积图的 X 和 Y 轴，并为其设置标签。在我们的示例中，X 轴表示面积，Y 轴表示重量。

Define the X and Y axis of the area chart and set labels to them in start() method of Application class. In our example, X axis represents area and the Y axis represents weights.

public class ClassName extends Application {
   @Override
   public void start(Stage primaryStage) throws Exception {
      //Defining the x axis
      NumberAxis xAxis = new NumberAxis(0, 12, 3);
      xAxis.setLabel("Area");

      //Defining the y axis
      NumberAxis yAxis = new NumberAxis(0, 16, 4);
      yAxis.setLabel("Weight");
   }
}

Step 2: Creating the Scatter Chart

通过实例化包 javafx.scene.chart 中名为 ScatterChart 的类创建折线图。将表示在上一步骤中创建的 X 轴和 Y 轴的对象传递给此类的构造函数。

Create a line chart by instantiating the class named ScatterChart 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 Scatter chart
ScatterChart<String, Number> scatterChart = new ScatterChart(xAxis, yAxis);

Step 3: Preparing the Data

实例化 XYChart.Series 类并将数据（系列、x 和 y 坐标）添加到此类的可观察列表中，如下所示 −

Instantiate the XYChart.Series class and 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 series = new XYChart.Series();
series.getData().add(new XYChart.Data(8, 12));
series.getData().add(new XYChart.Data(4, 5.5));
series.getData().add(new XYChart.Data(11, 14));
series.getData().add(new XYChart.Data(4, 5));
series.getData().add(new XYChart.Data(3, 3.5));
series.getData().add(new XYChart.Data(6.5, 7));

Step 4: Add Data to the Scatter Chart

将上一步骤中准备的数据系列添加到散点图，如下所示 −

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

//Setting the data to scatter chart
scatterChart.getData().addAll(series);

Step 5: Creating a Group Object

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

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

将上一步骤中创建的 ScatterChart（节点）对象作为参数传递给 Group 类的构造函数。应这样做，以便将其添加到组中，如下所示 −

Pass the ScatterChart (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(scatterChart);

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

下表包含按面积和重量绘制的示例数据。

The following table contains sample data plotted between area and weight.

Area	Weight
8	12
4	5.5
11	14
4	5
3	3.5
6.5	7

以下是使用 JavaFX 生成描绘以上数据的散点图的 Java 程序。

Following is a Java program which generates a scatter chart depicting the above data using JavaFX.

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

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

import javafx.application.Application;
import static javafx.application.Application.launch;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.ScatterChart;
import javafx.scene.chart.XYChart;

public class ScatterChartExample extends Application {
   @Override
   public void start(Stage stage) {
      //Defining the axes
      NumberAxis xAxis = new NumberAxis(0, 12, 3);
      xAxis.setLabel("Area");

      NumberAxis yAxis = new NumberAxis(0, 16, 4);
      yAxis.setLabel("Weight");

      //Creating the Scatter chart
      ScatterChart<String, Number> scatterChart =
      new ScatterChart(xAxis, yAxis);

      //Prepare XYChart.Series objects by setting data
      XYChart.Series series = new XYChart.Series();
      series.getData().add(new XYChart.Data(8, 12));
      series.getData().add(new XYChart.Data(4, 5.5));
      series.getData().add(new XYChart.Data(11, 14));
      series.getData().add(new XYChart.Data(4, 5));
      series.getData().add(new XYChart.Data(3, 3.5));
      series.getData().add(new XYChart.Data(6.5, 7));

      //Setting the data to scatter chart
      scatterChart.getData().addAll(series);

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

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

      //Setting title to the Stage
      stage.setTitle("Scatter 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 ScatterChartExample.java
java --module-path %PATH_TO_FX% --add-modules javafx.controls ScatterChartExample

在执行时，上述程序生成一个 JavaFX 窗口，显示如下所示的散点图。

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

Example

下表说明了每个月售出的电子设备数量。

The following table illustrates the number of electronic items that were in sold per month.

Item	Number of Sales (Per Month)
Laptop	176
TV	30
Mobile	540
Smart Watch	250
MacBook	60

以下是使用 JavaFX 生成描绘以上数据的散点图的 Java 程序。

Following is a Java program which generates a scatter chart depicting the above data using JavaFX.

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

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

import javafx.application.Application;
import static javafx.application.Application.launch;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.CategoryAxis;
import javafx.scene.chart.ScatterChart;
import javafx.scene.chart.XYChart;

public class ScatterChartExample extends Application {
   @Override
   public void start(Stage stage) {
      //Defining the axes
      CategoryAxis xAxis = new CategoryAxis();
      xAxis.setLabel("Items");

      NumberAxis yAxis = new NumberAxis();
      yAxis.setLabel("Sales (per month)");

      //Creating the Scatter chart
      ScatterChart scatterChart =
      new ScatterChart(xAxis, yAxis);

      //Prepare XYChart.Series objects by setting data
      XYChart.Series series = new XYChart.Series();
      series.setName("Items sold per month");

      series.getData().add(new XYChart.Data("Laptop", 176));
      series.getData().add(new XYChart.Data("TV", 30));
      series.getData().add(new XYChart.Data("Mobile", 540));
      series.getData().add(new XYChart.Data("Smart Watch", 250));
      series.getData().add(new XYChart.Data("MacBook", 60));

      //Setting the data to scatter chart
      scatterChart.getData().addAll(series);

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

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

      //Setting title to the Stage
      stage.setTitle("Scatter 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);
   }
}