在图表中按日期排序X轴 - JavaFX

请注意，格式您使用的（YYYY-MM-DD）具有非常好的属性，格式化字符串的字典顺序与日期的顺序相同。所以在x轴上排列字符串就足够了。我可以看到的最简单的方法是使用类别轴，只需使用 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中时，数据在图表中保持正确排序。

Note that the format you're using (YYYY-MM-DD) has the very nice property that the lexicographical order of the formatted string is identical to the order of the dates. So it's enough to order the strings on the x-axis here. The easiest way to do this I can see is to use a Category axis, and just use supply a SortedList<Data<String, Number>> to the series for the chart. Then when you add any data to the underlying list, the data remains correctly ordered in the chart.

这是一个SSCCE。在这个例子中，我给任何给定的日期只有一个值。 addData（...）方法创建一个新的数据点（如果该数据点不存在）或将y值添加到现有数据点。

Here's a SSCCE. In this example, I only have one value for any given date. The addData(...) method either creates a new data point (if none exists with that date) or adds the y-value to the existing data point.

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);
    }
}

如果要使用没有很好订单的格式 - 保留属性，您只需要将字符串解析为比较器中的日期，并比较日期。例如。如果你有一些类似

If you want to use a format without the nice order-preserving property, you just need to parse the strings back to dates in the comparator, and compare the dates. E.g. if you had something like

formatter = DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM) ;

它可以与

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);
});

这样做的正确方式是使数据类型为 LocalDate ，即您将有一个 LineChart< LocalDate，Number> ：但是定义一个 Axis< LocalDate> code>似乎比这应该是更多的工作。

The "correct" way to do this would be to make the data type a LocalDate, i.e. you would have a LineChart<LocalDate, Number>: however defining an Axis<LocalDate> seems to be way more work than it should be.