如何按日期对LineChart X轴进行排序？

现在我的LineChart像这样

我试图削减日期并将其转换为int,但是现在我不知道该怎么办…

    datesToCompare.addAll(LastHoursAndDates.keySet()); // dates in String eg. 2015-12-25
    List<Integer> year = new ArrayList<Integer>(); // list for year after split
    List<Integer> month = new ArrayList<Integer>();// list for month after split
    List<Integer> days = new ArrayList<Integer>(); // list for days after split

    for(int i =0;i < LastHoursAndDates.size();i++)
    {
            sorting = datesToCompare.get(i).split("-");
            year.add(Integer.valueOf(sorting[0]));
            month.add(Integer.valueOf(sorting[1]));
            days.add(Integer.valueOf(sorting[2]));

                for(int j =0;j < LastHoursAndDates.size();j++)
                {
                    if(year.get(i) == year.get(j))
                    {
                        if(month.get(i) == month.get(j))
                        {
                            //???????
                        }
                    }
                }



}//for

也许有人遇到过同样的问题？

解决方法:

请注意,您使用的格式(YYYY-MM-DD)具有很好的属性,即格式化字符串的字典顺序与日期顺序相同.因此,在此处在x轴上排序字符串就足够了.我看到的最简单的方法是使用“类别”轴,并仅使用提供SortedList< Data< String,Number>>到图表的系列.然后,当您将任何数据添加到基础列表时,数据在图表中仍然保持正确的顺序.

这是SSCCE.在此示例中,对于任何给定日期,我只有一个值. addData(…)方法要么创建一个新的数据点(如果在该日期不存在),要么将y值添加到现有数据点.

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.Random;

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.collections.transformation.SortedList;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.chart.CategoryAxis;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart.Data;
import javafx.scene.chart.XYChart.Series;
import javafx.scene.control.Button;
import javafx.scene.control.DatePicker;
import javafx.scene.control.Spinner;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

public class LineChartWithDatesAsStrings extends Application {

    private DateTimeFormatter formatter = DateTimeFormatter.ISO_LOCAL_DATE ;

    @Override
    public void start(Stage primaryStage) {
        CategoryAxis xAxis = new CategoryAxis();
        NumberAxis yAxis = new NumberAxis();

        ObservableList<Data<String, Number>> data = FXCollections.observableArrayList() ;
        SortedList<Data<String, Number>> sortedData = new SortedList<>(data, (data1, data2) -> 
                data1.getXValue().compareTo(data2.getXValue()));

        LineChart<String, Number> chart = new LineChart<>(xAxis, yAxis);
        chart.getData().add(new Series<>(sortedData));
        chart.setAnimated(false);

        final int dayRange = 60 ;
        LocalDate today = LocalDate.now() ;
        Random rng = new Random();

        for (int i = 0; i < 20 ; i++) {
            LocalDate date = today.minusDays(rng.nextInt(dayRange));
            String formattedDate = formatter.format(date);
            double value = rng.nextDouble() ;

            addData(data, formattedDate, value);
        }

        DatePicker datePicker = new DatePicker();
        Spinner<Double> valuePicker = new Spinner<>(0.0, 1.0, 0, 0.1);
        valuePicker.setEditable(true);

        Button addButton = new Button("Add");
        addButton.setOnAction(e -> addData(data, formatter.format(datePicker.getValue()), valuePicker.getValue()));

        HBox controls = new HBox(5, datePicker, valuePicker, addButton);
        controls.setAlignment(Pos.CENTER);
        controls.setPadding(new Insets(5));

        BorderPane root = new BorderPane(chart, null, null, controls, null);
        primaryStage.setScene(new Scene(root, 600, 600));
        primaryStage.show();
    }

    private void addData(ObservableList<Data<String, Number>> data, String formattedDate, double value) {
        Data<String, Number> dataAtDate = data.stream()
            .filter(d -> d.getXValue().equals(formattedDate))
            .findAny()
            .orElseGet(() -> {
                Data<String, Number> newData = new Data<String, Number>(formattedDate, 0.0);
                data.add(newData);
                return newData ;
            }) ;
        dataAtDate.setYValue(dataAtDate.getYValue().doubleValue() + value);
    }

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

如果要使用不具有良好顺序保留属性的格式,则只需要在比较器中将字符串解析回日期,然后比较日期即可.例如.如果你有类似的东西

formatter = DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM) ;

它会与

SortedList<Data<String, Number>> sortedData = new SortedList<>(data, (data1, data2) -> {
    LocalDate date1 = LocalDate.parse(data1.getXValue(), formatter);
    LocalDate date2 = LocalDate.parse(data2.getXValue(), formatter);
    return date1.compareTo(date2);
});

做到这一点的“正确”方法是使数据类型成为LocalDate,即您将具有LineChart< LocalDate,Number&gt ;：然而,定义一个Axis< LocalDate>即可.似乎比应做的工作还多.