如何创建一个包含重复条目的 XYChart.Series 的可观察列表

Question

我想用数据库中的数据填充折线图。为此，我创建了一个 class，returns 一个 ObservableList。但是我很难合并相同的 XYChart.Series 名称 （如下例所示）.

MVCE

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.chart.CategoryAxis;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
import javafx.stage.Stage;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Sample extends Application {
    @Override public void start(Stage stage) {
        //create the chart
        final CategoryAxis xAxis = new CategoryAxis();
        final NumberAxis yAxis = new NumberAxis();
        xAxis.setLabel("Year");

        final LineChart<String,Number> lineChart =
                new LineChart<>(xAxis, yAxis);

        lineChart.setTitle("Employment Monitoring, 2020");

        for(XYChart.Series series : getData()){
            lineChart.getData().add(series);
        }

        // show the scene.
        Scene scene = new Scene(lineChart, 800, 600);
        stage.setScene(scene);
        stage.show();
    }

    /* How can I return the right value to the line chart ? */
    private ObservableList<XYChart.Series> getData(){
        var list = FXCollections.<XYChart.Series>observableArrayList();
        
        // Supposed that this data where values retrieved from the database
        ArrayList<List> arrayList = new ArrayList<>();
        arrayList.add(Arrays.asList("Permanent", "2011", 5));
        arrayList.add(Arrays.asList("Job Order", "2011", 16));
        arrayList.add(Arrays.asList("Permanent", "2012", 10));
        arrayList.add(Arrays.asList("Job Order", "2012", 19));

        for (List obs : arrayList){
            list.add(
                    new XYChart.Series(
                            (String) obs.get(0),
                            FXCollections.observableArrayList(
                                    new XYChart.Data<>((String) obs.get(1), (Number) obs.get(2))
                            )
                    ));
        }
        return list;
    }

    public static void main(String[] args) { launch(args); }
}

这将产生这个输出

如您所见，Permanent 和 Job Order

有重复的系列

问题是

我将如何合并重复的条目以便获得下面的输出？

without using a model class

编辑

正如@kleopatra 所说，（根据我目前对 java 的了解） 我尝试通过以下方式过滤列表中的数据：

for (XYChart.Series series : getData()){
    XYChart.Data item = (XYChart.Data) series.getData().get(0);
    
    if (lineChart.getData().size() > 0){
        for (XYChart.Series duplicate : lineChart.getData()) 
        {
            if (duplicate.getName().equals(series.getName()))
            {
                duplicate.getData().add(item);
            } else {
               // lineChart.getData().add(series);
            }
        }
    } else {
        lineChart.getData().add(series);
    }
}

而不仅仅是：

for(XYChart.Series series : getData())
{
    lineChart.getData().add(series);
}

尽管它为我提供了 Permanent 系列的串联输出（这是我想要实现的）。我几乎不能添加另一个系列，例如Job Order 到折线图。就像我在 else 条件下取消注释代码一样。我收到一个错误。

ConcurrentModificationException

Answer 1

使用@kleopatra 的想法，您可以过滤列表并使用过滤后的数据创建 Series。您的要求使事情复杂化。 Arrays.asList("Permanent", "2011", 5) 也使事情复杂化。在 Java 中创建不同类型的 List 是不好的做法。在我的示例中，我使用 HashMap 来过滤数据。

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.chart.CategoryAxis;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
import javafx.stage.Stage;

public class App extends Application
{

    @Override
    public void start(Stage stage)
    {
        //create the chart
        final CategoryAxis xAxis = new CategoryAxis();
        final NumberAxis yAxis = new NumberAxis();
        xAxis.setLabel("Year");

        final LineChart<String, Number> lineChart
                = new LineChart<>(xAxis, yAxis);

        lineChart.setTitle("Employment Monitoring, 2020");
        lineChart.getData().addAll(getData());
        

        // show the scene.
        Scene scene = new Scene(lineChart, 800, 600);
        stage.setScene(scene);
        stage.show();
    }

    /* How can I return the right value to the line chart ? */
    private List<XYChart.Series<String, Number>> getData()
    {
        List<XYChart.Series<String, Number>> series = new ArrayList();

        // Supposed that this data where values retrieved from the database
        List<List> items = new ArrayList<>();
        items.add(Arrays.asList("Permanent", "2011", 5));
        items.add(Arrays.asList("Job Order", "2011", 16));
        items.add(Arrays.asList("Permanent", "2012", 10));
        items.add(Arrays.asList("Job Order", "2012", 19));

        Map<String, List> map = new HashMap();
        for (int i = 0; i < items.size(); i++) {
            if (map.get(items.get(i).get(0).toString()) == null) {
                List newEntry = new ArrayList();
                newEntry.add(items.get(i).get(1));
                newEntry.add(items.get(i).get(2));
                map.put(items.get(i).get(0).toString(), newEntry);
                System.out.println("Createing array " + items.get(i).get(0).toString() + "  Adding " + items.get(i).get(1) + ":" + items.get(i).get(2));
            }
            else {
                List oldList = map.get(items.get(i).get(0).toString());
                oldList.add(items.get(i).get(1));
                oldList.add(items.get(i).get(2));
                System.out.println("Adding to array " + items.get(i).get(0).toString() + "  Adding " + items.get(i).get(1) + ":" + items.get(i).get(2));
            }
        }

        for (Map.Entry<String, List> entry : map.entrySet()) {
            XYChart.Series<String, Number> tempItemsSeries = new XYChart.Series();
            tempItemsSeries.setName(entry.getKey());

            //System.out.println(entry.getValue().size() + Arrays.toString(entry.getValue().toArray()));
            for (int i = 0; i < entry.getValue().size(); i = i + 2) {
                tempItemsSeries.getData().add(new XYChart.Data(entry.getValue().get(i), entry.getValue().get(i + 1)));
            }
            series.add(tempItemsSeries);
        }

        return series;
    }

    public static void main(String[] args)
    {
        launch(args);
    }
}

如何创建一个包含重复条目的 XYChart.Series 的可观察列表

How to create an observable list of XYChart.Series that combines duplicate entry

javafx

linechart

observablelist

问题是

编辑