menus.md

Menus

Menus consists of basically three components:

• menu bar - contains one or more drop-down menus
• menu - contains one or more menu items
• menu item - a label associated with an action

The menu bar itself is just a panel with buttons that pop up an action-list-like dialog window beneath the button, aka the menu, that just got clicked. This dialog window contains all the menu items that were added to this menu. The menu can be closed by pressing the ESC key on the keyboard.

You can either add menu items using objects that implement the Runnable interface via the addMenuItem(Runnable) method or call the addMenuItem(String,Runnable) method which will take a separate label and not derive it from the toString() of the Runnable.

To add a sub-menu, you can create a add another Menu as a menu item to another Menu using the addSubMenu(Menu) method.

In the following example, a menu bar with two menus, File and Help, is created, each containing two menu items:

        MenuBar menubar = new MenuBar();

        // "File" menu
        Menu menuFile = new Menu("File");
        menubar.addMenu(menuFile);
        menuFile.addMenuItem("Open...", new Runnable() {
            public void run() {
                File file = new FileDialogBuilder().build().showDialog(textGUI);
                if (file != null)
                    MessageDialog.showMessageDialog(
                            textGUI, "Open", "Selected file:\n" + file, MessageDialogButton.OK);
            }
        });
        menuFile.addMenuItem("Exit", new Runnable() {
            public void run() {
                System.exit(0);
            }
        });

        // "Help" menu
        Menu menuHelp = new Menu("Help");
        menubar.addMenu(menuHelp);
        menuHelp.addMenuItem("Homepage", new Runnable() {
            public void run() {
                MessageDialog.showMessageDialog(
                        textGUI, "Homepage", "https://github.com/mabe02/lanterna", MessageDialogButton.OK);
            }
        });
        menuHelp.addMenuItem("About", new Runnable() {
            public void run() {
                MessageDialog.showMessageDialog(
                        textGUI, "About", "Lanterna drop-down menu", MessageDialogButton.OK);
            }
        });

        // Create window to hold the panel
        BasicWindow window = new BasicWindow();
        window.setComponent(menubar);

        textGUI.addWindow(window);

Screenshot