Show pies percentage of PieChart - javafx

Question

For the MVCE underneath, how can you add a label on each pie in the piechart that shows its percentage of the total pie? In the JavaDoc they only add a % after the value, which isn't any solution.
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

All you have to do is iterate through the pie chart data and add up the values to get the total. Then divide the current value by the total.
Adapting the (awful) example from the link you provided:
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);
}
}
If you want to avoid recomputing the total every time there's a mouse event, you can create a DoubleBinding to store it:
DoubleBinding total = Bindings.createDoubleBinding(() ->
pieChartData.stream().collect(Collectors.summingDouble(PieChart.Data::getPieValue)), pieChartData);
and then just
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);
}
);
}