Getting size of FXML generated nodes - javafx

Question

I want to get the size of a node, after it has been sized properly, which I understand is done after the stage is shown. however, i cannot do it in start() method, because the node is not initialized yet, because its loaded it from an FXML file.
If I implement Initializable Interface and try to get the size in initialize() method, it returns 0.0
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.BorderPane?>
<GridPane xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8" fx:controller="musicPlayer.Test">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
<children>
<TableView fx:id="testNode">
<columns>
<TableColumn prefWidth="75.0" text="C1" />
<TableColumn prefWidth="75.0" text="C2" />
</columns>
</TableView>
</children>
</GridPane>
just an arbitrary node in a grid pane generated with scene builder
public class Test extends Application implements Initializable {
#FXML
private TableView testNode;
public void initialize(URL location, ResourceBundle resources) {
//System.out.println(testNode.getWidth()); is always 0.0
}
public void start(Stage primaryStage) throws Exception {
Parent root = FXMLLoader.load(getClass().getResource("test.fxml"));
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.show();
//System.out.println(testNode.getWidth()); throws Nullpointer Exception
}
public static void main(String[] args) {
launch(args);
}
}
I've also tried adding a listener to the stage, but i still get a nullpointer exception.
Is there a way of getting the size, without using a sleeping thread?