CustomMenuControllerView.xml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import custommenu.view.ContextMenuPane?>

<AnchorPane xmlns:fx="http://javafx.com/fxml" fx:controller="custommenu.controller.CustomMenuController">
    <children>
        <VBox fx:id="vbox" onContextMenuRequested="#showMenu"
            onMousePressed="#hideMenu" prefHeight="200" prefWidth="200">
        </VBox>
        
        <!-- this lets you skip the ContextMenuPane class, but requires all your wiring be done by your controller -->
        <!-- scene builder will render this file and simply skip this block -->
        <fx:define>
            <ContextMenu fx:id="menu">
                <items>
                    <MenuItem text="add" onAction="#add" />
                </items>
            </ContextMenu>
        </fx:define>
    </children>
</AnchorPane>