JavaFX ContextMenu with only MenuItems not displaying

Question

I'm learning JavaFX by working through the book "JavaFX 8: Introduction by Example". I'm working on the section on Key Combinations and Context Menus and have hit a problem. The example I'm exploring creates a window with a simple menu to which key combinations have been assigned and a central area that lists the various key combinations available. When you press one of the combinations the window shows just the combination you pressed. All fine and good so far. However the code also defines a context menu that displays (should display) a single menu item on right-click. In fact is doesn't display anything.

I've run Debug on the code and the relevant line is executed. I've tried assigning other menu items and I've tried assigning the menu items using .addAll(...) rather than when the Context Menu is instantiated. None of them has made any difference.

However when I assign a Menu to the Context Menu, either when creating the instance or using .addAll, it works correctly.

I've looked up the Java documentation for ContextMenu (JavaFX 8 ContextMenu ) and it clearly shows Menu Items being assigned to the Context Menu so I'm rather stuck. Can anyone advise please? The relevant lines are at the bottom of the code below.

Thanks.

package jfx8ibe;

import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.scene.Scene;
import javafx.scene.control.ContextMenu;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuBar;
import javafx.scene.control.MenuItem;
import javafx.scene.control.SeparatorMenuItem;
import javafx.scene.effect.InnerShadow;
import javafx.scene.input.KeyCode;
import javafx.scene.input.KeyCodeCombination;
import javafx.scene.input.KeyCombination;
import javafx.scene.input.MouseButton;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.BorderPane;
import javafx.scene.paint.Color;
import javafx.scene.text.Font;
import javafx.scene.text.FontWeight;
import javafx.scene.text.Text;
import javafx.stage.Stage;

/**
 *
 * @author cdea
 */
public class KeyCombinationsAndContextMenus extends Application {

    @Override
    public void start(Stage primaryStage) {
        BorderPane root = new BorderPane();
        Scene scene = new Scene(root, 530, 350, Color.WHITE);

        final StringProperty statusProperty = new SimpleStringProperty();

        InnerShadow iShadow = new InnerShadow();
        iShadow.setOffsetX(3.5f);
        iShadow.setOffsetY(3.5f);
        final Text status = new Text();
        status.setEffect(iShadow);
        status.setX(100);
        status.setY(50);
        status.setFill(Color.LIME);
        status.setFont(Font.font(null, FontWeight.BOLD, 35));
        //status.setTranslateY(50);

        status.textProperty().bind(statusProperty);
        statusProperty.set("Keyboard Shortcuts\n"
                + "Ctrl-N, \n"
                + "Ctrl-S, \n"
                + "Ctrl-X \n"
                + "Ctrl-Shift-E");
        root.setCenter(status);

        MenuBar menuBar = new MenuBar();
        menuBar.prefWidthProperty()
               .bind(primaryStage.widthProperty());
        root.setTop(menuBar);

        Menu fileMenu = new Menu("_File");
        fileMenu.setMnemonicParsing(true);
        menuBar.getMenus().add(fileMenu);

        MenuItem newItem = new MenuItem("_New");       
        newItem.setMnemonicParsing(true);

        newItem.setAccelerator(new KeyCodeCombination(KeyCode.N, 
                KeyCombination.SHORTCUT_DOWN));
        newItem.setOnAction(actionEvent -> statusProperty.set("Ctrl-N"));
        fileMenu.getItems().add(newItem);

        MenuItem saveItem = new MenuItem("_Save");
        saveItem.setMnemonicParsing(true);
        saveItem.setAccelerator(new KeyCodeCombination(KeyCode.S, 
                KeyCombination.SHORTCUT_DOWN));
        saveItem.setOnAction(actionEvent -> statusProperty.set("Ctrl-S"));
        fileMenu.getItems().add(saveItem);

        fileMenu.getItems().add(new SeparatorMenuItem());

        MenuItem exitItem = new MenuItem("Exit");
        exitItem.setAccelerator(new KeyCodeCombination(KeyCode.X, 
                KeyCombination.SHORTCUT_DOWN));

        exitItem.setOnAction(actionEvent -> {
            statusProperty.set("Ctrl-X");
            Platform.exit();
        });

        scene.getAccelerators().put(
                new KeyCodeCombination(KeyCode.E, 
                                       KeyCombination.SHORTCUT_DOWN, 
                                       KeyCombination.SHIFT_DOWN),
                () -> statusProperty.set("Ctrl-Shift-E")
        );

        fileMenu.getItems().add(exitItem);

        ContextMenu contextFileMenu = new ContextMenu(exitItem);

        primaryStage.addEventHandler(MouseEvent.MOUSE_CLICKED, (MouseEvent me) -> {
            if (me.getButton() == MouseButton.SECONDARY) {
                contextFileMenu.show(root, me.getScreenX(), me.getScreenY());
            } else {
                contextFileMenu.hide();
            }
        });


        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }

}

Answer 1

You can't add the same menu item to two different menus. Since your exit item is already in the file menu, it won't appear in the context menu.

To reuse the functionality in different places like this, I'd recommend using the ControlsFX framework, in particular the actions API, on top of JavaFX.

E.g.

Action exitAction = new Action("Exit", event -> {
    statusProperty.set("Ctrl-X");
    Platform.exit();
});
exitAction.setAccelerator(new KeyCodeCombination(KeyCode.X, 
       KeyCombination.SHORTCUT_DOWN));

fileMenu.getItems().add(ActionUtils.createMenuItem(exitAction));

ContextMenu contextFileMenu = new ContextMenu(ActionUtils.createMenuItem(exitAction));