Question

对于下面的MVCE，如何在饼图中的每个饼上添加一个标签，显示其总馅饼的百分比？在JavaDoc中，他们只在值后添加％，这不是任何解决方案。

public class PieChartSample extends Application {

    @Override public void start(Stage stage) {
        Scene scene = new Scene(new Group());
        stage.setTitle("Imported Fruits");
        stage.setWidth(500);
        stage.setHeight(500);

        ObservableList<PieChart.Data> pieChartData =
                FXCollections.observableArrayList(
                new PieChart.Data("Grapefruit", 13),
                new PieChart.Data("Oranges", 25),
                new PieChart.Data("Plums", 10),
                new PieChart.Data("Pears", 22),
                new PieChart.Data("Apples", 30));
        final PieChart chart = new PieChart(pieChartData);
        chart.setTitle("Imported Fruits");

        ((Group) scene.getRoot()).getChildren().add(chart);
        stage.setScene(scene);
        stage.show();
    }

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

Answer 1

您所要做的就是遍历饼图数据并将值相加以获得总数。然后将当前值除以总数。

从您提供的链接调整（糟糕）示例：

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.chart.PieChart;
import javafx.scene.control.Label;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class PieChartSample extends Application {

    @Override public void start(Stage stage) {
        Pane root = new Pane();
        Scene scene = new Scene(root);
        stage.setTitle("Imported Fruits");
        stage.setWidth(500);
        stage.setHeight(500);

        ObservableList<PieChart.Data> pieChartData =
                FXCollections.observableArrayList(
                new PieChart.Data("Grapefruit", 13),
                new PieChart.Data("Oranges", 25),
                new PieChart.Data("Plums", 10),
                new PieChart.Data("Pears", 22),
                new PieChart.Data("Apples", 30));
        final PieChart chart = new PieChart(pieChartData);
        chart.setTitle("Imported Fruits");

        final Label caption = new Label("");
        caption.setTextFill(Color.DARKORANGE);
        caption.setStyle("-fx-font: 24 arial;");

        for (final PieChart.Data data : chart.getData()) {
            data.getNode().addEventHandler(MouseEvent.MOUSE_PRESSED,
                e -> {
                    double total = 0;
                    for (PieChart.Data d : chart.getData()) {
                        total += d.getPieValue();
                    }
                    caption.setTranslateX(e.getSceneX());
                    caption.setTranslateY(e.getSceneY());
                    String text = String.format("%.1f%%", 100*data.getPieValue()/total) ;
                    caption.setText(text);
                 }
                );
        }

        root.getChildren().addAll(chart, caption);
        stage.setScene(scene);
        stage.show();
    }

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

如果您想避免每次鼠标事件时重新计算总数，您可以创建DoubleBinding来存储它：

    DoubleBinding total = Bindings.createDoubleBinding(() ->
        pieChartData.stream().collect(Collectors.summingDouble(PieChart.Data::getPieValue)), pieChartData);

然后只是

    for (final PieChart.Data data : chart.getData()) {
        data.getNode().addEventHandler(MouseEvent.MOUSE_PRESSED,
            e -> {
                caption.setTranslateX(e.getSceneX());
                caption.setTranslateY(e.getSceneY());
                String text = String.format("%.1f%%", 100*data.getPieValue()/total.get()) ;
                caption.setText(text);
             }
            );
    }

显示PieChart的馅饼百分比

1 个答案: