DoughnutChart.java

package mj.ocraptor.javafx;

import javafx.collections.ObservableList;
import javafx.geometry.Bounds;
import javafx.scene.Node;
import javafx.scene.chart.PieChart;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;

public class DoughnutChart extends PieChart {
  private final Circle innerCircle;

  public DoughnutChart(ObservableList<Data> pieData) {
    super(pieData);

    innerCircle = new Circle();

    // just styled in code for demo purposes,
    // use a style class instead to style via css.
    innerCircle.setFill(Color.WHITESMOKE);
    innerCircle.setStroke(Color.WHITE);
    innerCircle.setStrokeWidth(3);
  }

  @Override
  protected void layoutChartChildren(double top, double left, double contentWidth,
      double contentHeight) {
    super.layoutChartChildren(top, left, contentWidth, contentHeight);

    addInnerCircleIfNotPresent();
    updateInnerCircleLayout();
  }

  private void addInnerCircleIfNotPresent() {
    if (getData().size() > 0) {
      Node pie = getData().get(0).getNode();
      if (pie.getParent() instanceof Pane) {
        Pane parent = (Pane) pie.getParent();

        if (!parent.getChildren().contains(innerCircle)) {
          parent.getChildren().add(innerCircle);
        }
      }
    }
  }

  private void updateInnerCircleLayout() {
    double minX = Double.MAX_VALUE, minY = Double.MAX_VALUE;
    double maxX = Double.MIN_VALUE, maxY = Double.MIN_VALUE;
    for (PieChart.Data data : getData()) {
      Node node = data.getNode();

      Bounds bounds = node.getBoundsInParent();
      if (bounds.getMinX() < minX) {
        minX = bounds.getMinX();
      }
      if (bounds.getMinY() < minY) {
        minY = bounds.getMinY();
      }
      if (bounds.getMaxX() > maxX) {
        maxX = bounds.getMaxX();
      }
      if (bounds.getMaxY() > maxY) {
        maxY = bounds.getMaxY();
      }
    }

    innerCircle.setCenterX(minX + (maxX - minX) / 2);
    innerCircle.setCenterY(minY + (maxY - minY) / 2);

    innerCircle.setRadius((maxX - minX) / 4);
  }
}