Drawing lines between Shapes laid out in HBox and VBox - javafx

Question

I have a circle inside various containers (ScrollPane, Group, HBox and VBox)
I want to draw a line from 0,0 to the centre of the circle.
I think the code below shows the problem. There is some function unknown to me which should go
in //SOME CODE HERE TO WORK OUT WHERE THE CIRCLE IS to make it work
I have a sample application I wrote to simplify my problem.
import java.util.Random;
import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.ScrollPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.scene.shape.Circle;
import javafx.scene.shape.Line;
import javafx.stage.Stage;
public class TestAppForCoords extends Application {
//Scene Graph:
//ScrollPane - scroll
// - Group - root
// - HBox - hbox - with random padding
// - VBox
// - VBox - vbox - with random padding
// - Circle - circle
// - VBox
// - Group - lines
// - Line - line
#Override
public void start(final Stage primaryStage) throws Exception {
Random rand = new Random();
int randomNum1 = rand.nextInt((100 - 0) + 1) + 0;
int randomNum2 = rand.nextInt((100 - 0) + 1) + 0;
System.out.println(randomNum1);
System.out.println(randomNum2);
ScrollPane scroll = new ScrollPane();
scroll.setPrefSize(500, 300);
Scene scene = new Scene(scroll);
primaryStage.setScene(scene);
Group root = new Group();
HBox hbox = new HBox();
hbox.setPadding(new Insets(randomNum1));
VBox vbox = new VBox();
hbox.getChildren().add(new VBox());
vbox.setPadding(new Insets(randomNum2));
hbox.getChildren().add(vbox);
hbox.getChildren().add(new VBox());
Circle circle = new Circle();
circle.setRadius(10);
vbox.getChildren().add(circle);
Group lines = new Group();
root.getChildren().add(hbox);
root.getChildren().add(lines);
root.autosize();
Line line = new Line();
line.setStartX(0);
line.setStartY(0);
//SOME CODE HERE TO WORK OUT WHERE THE CIRCLE IS
line.setEndX(123);
line.setEndY(123);
lines.getChildren().add(line);
scroll.setContent(root);
primaryStage.show();
}
public static void main(String[] args) {
System.out.println("Start JavaFXTestApp");
launch(args);
System.out.println("End JavaFXTestApp");
}
}

Answer 1

Finally I have it working. I can add a setOnShown handler which is called to correct the line.
So I have found out that localToScene and sceneToLocal only work after the window is being displayed
primaryStage.setOnShown(new EventHandler<WindowEvent>() {
#Override
public void handle(WindowEvent arg0) {
Point2D p = circle.localToScene(circle.getCenterX(),circle.getCenterY());
p = line.sceneToLocal(p);
line.setEndX(p.getX());
line.setEndY(p.getY());
}
});
So the final working program is:
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.geometry.Point2D;
import javafx.scene.Group;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ScrollPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.scene.shape.Circle;
import javafx.scene.shape.Line;
import javafx.stage.Stage;
import javafx.stage.WindowEvent;
public class TestAppForCoords extends Application {
//Scene Graph:
//ScrollPane - scroll
// - Group - root
// - VBox - vboxEXTRA - with random padding
// - HBox - hbox - with random padding
// - VBox
// - VBox - vbox - with random padding
// - Circle - circle
// - VBox
// - Group - lines
// - Line - line
Line line = new Line();
Circle circle = new Circle();
#Override
public void start(final Stage primaryStage) throws Exception {
Random rand = new Random();
int randomNum1 = rand.nextInt((100 - 0) + 1) + 0;
int randomNum2 = rand.nextInt((100 - 0) + 1) + 0;
int randomNum3 = rand.nextInt((100 - 0) + 1) + 0;
System.out.println(randomNum1);
System.out.println(randomNum2);
System.out.println(randomNum3);
ScrollPane scroll = new ScrollPane();
scroll.setPrefSize(500, 300);
Scene scene = new Scene(scroll);
primaryStage.setScene(scene);
Group root = new Group();
HBox hbox = new HBox();
hbox.setPadding(new Insets(randomNum1));
VBox vbox = new VBox();
hbox.getChildren().add(new VBox());
vbox.setPadding(new Insets(randomNum2));
hbox.getChildren().add(vbox);
hbox.getChildren().add(new VBox());
circle.setRadius(10);
vbox.getChildren().add(circle);
Group lines = new Group();
root.getChildren().add(hbox);
root.getChildren().add(lines);
root.autosize();
root.requestLayout();
lines.getChildren().add(line);
VBox vboxEXTRA = new VBox();
vboxEXTRA.setPadding(new Insets(randomNum3));
vboxEXTRA.getChildren().add(root);
scroll.setContent(vboxEXTRA);
line.setStartX(0);
line.setStartY(0);
//This dosen't work prob because we aren't drawing yet
Point2D p = circle.localToScene(circle.getCenterX(),circle.getCenterY());
p = line.sceneToLocal(p);
line.setEndX(p.getX());
line.setEndY(p.getY());
primaryStage.setOnShown(new EventHandler<WindowEvent>() {
#Override
public void handle(WindowEvent arg0) {
Point2D p = circle.localToScene(circle.getCenterX(),circle.getCenterY());
p = line.sceneToLocal(p);
line.setEndX(p.getX());
line.setEndY(p.getY());
}
});
primaryStage.show();
}
public static void main(String[] args) {
System.out.println("Start JavaFXTestApp");
launch(args);
System.out.println("End JavaFXTestApp");
}
}