java - 将数据动态添加到 LineChart JavaFX

Question

我想在 LineChart 中设置一些值，但出现错误:添加了重复系列，或 NPE(我尝试清除我的系列列表，调用retainAll，但没有任何结果有帮助)在我的 Controller 类中，我存储了我的 chart 实例

 public static void loadToJSON(LocalDate startDate,LocalDate endDate,Controller controller) {



    Task<Integer> task = new Task<Integer>() {
        @Override protected Integer call() throws Exception {
             double MIN_VAL=Double.MAX_VALUE;
             double MAX_VALUE=Double.MIN_VALUE;
            XYChart.Series<String,Number> series = new  XYChart.Series<String,Number>();


            for (LocalDate date = startDate;
                 !date.isEqual(endDate.plusDays(1));
                 date = date.plusDays(1)) {

                String formattedDate = date.format(DateTimeFormatter.ofPattern("yyyy-MM-dd"));

                URLConnection urlCon = null;

                String baseURL="http://api.fixer.io/";
                try {
                    URL url = new URL(baseURL+formattedDate+"?symbols=PLN,EUR");
                    urlCon = url.openConnection();

                    InputStreamReader in = new InputStreamReader(urlCon.getInputStream());
                    ObjectMapper mapper = new ObjectMapper();
                    ExchangeRate jsonObject = mapper.readValue(in, ExchangeRate.class);

                    if(MIN_VAL>jsonObject.getRates().get("PLN"))
                        MIN_VAL=jsonObject.getRates().get("PLN");
                    if(MAX_VALUE<jsonObject.getRates().get("PLN"))
                        MAX_VALUE=jsonObject.getRates().get("PLN");
                    in.close();

                      series.getData().clear();
                    series.getData().add(new XYChart.Data<String,Number>(formattedDate,jsonObject.getRates().get("PLN")));
         controller.chart.getData().add(series);

                    try {
                        Thread.sleep(200);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        controller.messageBox.setText("Best exchange rate : "+MIN_VAL + " \nWorst exchange rate : "+MAX_VALUE);
            return null;
        }
    };
    Thread th = new Thread(task);
    th.setDaemon(true);
    th.start();

Answer 1

您通过调用重复将相同的系列添加到图表中

controller.chart.getData().add(series);

在循环内。这将导致您描述的异常(“java.lang.IllegalArgumentException:添加了重复系列”)。

相反，您应该在循环开始之前添加一次系列，然后在循环内向其中添加数据。

您还违反了 JavaFX 的线程规则，因为您正在从后台线程修改图表。 UI 只能从 JavaFX 应用程序线程访问。因此，您应该将修改图表(以及系列，一旦添加到图表中)的调用包装在 Platform.runLater(...) 中:

public static void loadToJSON(LocalDate startDate, LocalDate endDate, Controller controller) {

    Task<Integer> task = new Task<Integer>() {
        @Override
        protected Integer call() throws Exception {
            double MIN_VAL = Double.MAX_VALUE;
            double MAX_VALUE = Double.MIN_VALUE;
            XYChart.Series<String, Number> series = new XYChart.Series<String, Number>();

            Platform.runLater(() -> controller.chart.getData().add(series));

            for (LocalDate date = startDate; !date.isEqual(endDate.plusDays(1)); date = date.plusDays(1)) {

                String formattedDate = date.format(DateTimeFormatter.ofPattern("yyyy-MM-dd"));

                URLConnection urlCon = null;

                String baseURL = "http://api.fixer.io/";
                try {
                    URL url = new URL(baseURL + formattedDate + "?symbols=PLN,EUR");
                    urlCon = url.openConnection();

                    InputStreamReader in = new InputStreamReader(urlCon.getInputStream());
                    ObjectMapper mapper = new ObjectMapper();
                    ExchangeRate jsonObject = mapper.readValue(in, ExchangeRate.class);

                    if (MIN_VAL > jsonObject.getRates().get("PLN"))
                        MIN_VAL = jsonObject.getRates().get("PLN");
                    if (MAX_VALUE < jsonObject.getRates().get("PLN"))
                        MAX_VALUE = jsonObject.getRates().get("PLN");
                    in.close();

                    // Not sure why you are doing this?
                    // series.getData().clear();


                    Plaform.runLater(() -> 
                        series.getData().add(new XYChart.Data<String, Number>(formattedDate, jsonObject.getRates().get("PLN"))));

                    // controller.chart.getData().add(series);

                    try {
                        Thread.sleep(200);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            Platform.runLater(() -> 
                    controller.messageBox.setText("Best exchange rate : " + MIN_VAL + " \nWorst exchange rate : " + MAX_VALUE));
            return null;
        }
    };
    Thread th = new Thread(task);
    th.setDaemon(true);
    th.start();
}