Question

In this part of the JRuby Swing programming tutorial, we will work with menus and toolbar.

A menubar is one of the most visible parts of the GUI application. It is a group of commands located in various menus. While in console applications you had to remember all those arcane commands, here we have most of the commands grouped into logical parts. There are accepted standards that further reduce the amount of time spending to learn a new application. Menus group commands that we can use in an application. Toolbars provide a quick access to the most frequently used commands.

Simple menu

The first example will show a simple menu.

#!/usr/local/bin/jruby

# ZetCode JRuby Swing tutorial
#
# This program creates a simple
# menu.
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: December 2010

include Java

import java.awt.event.KeyEvent
import javax.swing.JButton
import javax.swing.JFrame
import javax.swing.JMenuBar
import javax.swing.JMenuItem
import javax.swing.JMenu
import javax.swing.ImageIcon
import java.lang.System


class Example < JFrame
  
  def initialize
    super "Simple menu"
    
    self.initUI
  end
    
  def initUI
    
    menubar = JMenuBar.new
    icon = ImageIcon.new "exit.png"

    fileMenu = JMenu.new "File"
    fileMenu.setMnemonic KeyEvent::VK_F

    itemExit = JMenuItem.new "Exit", icon
    itemExit.addActionListener do |e|
      System.exit 0
    end
    
    itemExit.setMnemonic KeyEvent::VK_C
    itemExit.setToolTipText "Exit application"

    fileMenu.add itemExit

    menubar.add fileMenu

    self.setJMenuBar menubar  
    
    self.setDefaultCloseOperation JFrame::EXIT_ON_CLOSE
    self.setSize 250, 200
    self.setLocationRelativeTo nil
    self.setVisible true
  end
end

Example.new

Our example will show a menu with one item. By selecting the exit menu item we close the application.

menubar = JMenuBar.new

Here we create a menubar.

icon = ImageIcon.new "exit.png"

We will display an icon in the menu item.

fileMenu = JMenu.new "File"
fileMenu.setMnemonic KeyEvent::VK_F

We create a menu object. A menu is a popup window containing JMenuItem s. Menus are located on the menubar. The menus can be accessed via the keyboard as well. To bind a menu to a particular key, we use the setMnemonic method. In our case, the menu can be opened with the ALT+F shortcut.

itemExit = JMenuItem.new "Close", icon
itemExit.addActionListener do |e|
  System.exit 0
end

Here we create a JMenuItem . A menu item is an object shown in a popup window of the selected menu. We also provide a shortcut for the menu item and a tooltip as well.

fileMenu.add itemExit

A menu item is added to the menu.

menubar.add fileMenu

A menu is added to the menubar.

Figure: Simple menu

Submenu

A submenu is a menu plugged into another menu object. The next example demonstrates this.

#!/usr/local/bin/jruby

# ZetCode JRuby Swing tutorial
#
# This program creates a 
# submenu.
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: December 2010


include Java

import java.awt.event.KeyEvent
import java.awt.event.ActionEvent
import javax.swing.JFrame
import javax.swing.ImageIcon
import javax.swing.JMenuBar
import javax.swing.JMenu
import javax.swing.JMenuItem
import javax.swing.KeyStroke
import java.lang.System


class Example < JFrame
  
  def initialize
    super "Submenu"
    
    self.initUI
  end
    
  def initUI
    
    menubar = JMenuBar.new

    iconNew = ImageIcon.new "new.png"
    iconOpen = ImageIcon.new "open.png"
    iconSave = ImageIcon.new "save.png"
    iconExit = ImageIcon.new "exit.png"

    fileMenu = JMenu.new "File"
    fileMenu.setMnemonic KeyEvent::VK_F

    imp = JMenu.new "Import"
    imp.setMnemonic KeyEvent::VK_M

    newsf = JMenuItem.new "Import newsfeed list..."
    bookm = JMenuItem.new "Import bookmarks..."
    mail = JMenuItem.new "Import mail..."

    imp.add newsf
    imp.add bookm
    imp.add mail

    fileNew = JMenuItem.new "New", iconNew
    fileNew.setMnemonic KeyEvent::VK_N

    fileOpen = JMenuItem.new "Open", iconOpen
    fileNew.setMnemonic KeyEvent::VK_O

    fileSave = JMenuItem.new "Save", iconSave
    fileSave.setMnemonic KeyEvent::VK_S

    fileExit = JMenuItem.new "Exit", iconExit
    fileExit.addActionListener do |e|
      System.exit 0
    end
    
    fileExit.setMnemonic KeyEvent::VK_C
    fileExit.setToolTipText "Exit application"
    fileExit.setAccelerator KeyStroke.getKeyStroke KeyEvent::VK_W,
      ActionEvent::CTRL_MASK

    fileMenu.add fileNew
    fileMenu.add fileOpen
    fileMenu.add fileSave
    fileMenu.addSeparator
    fileMenu.add imp
    fileMenu.addSeparator
    fileMenu.add fileExit

    menubar.add fileMenu

    self.setJMenuBar menubar
    
    self.setDefaultCloseOperation JFrame::EXIT_ON_CLOSE
    self.setSize 320, 220
    self.setLocationRelativeTo nil
    self.setVisible true
  end   
end

Example.new

In the example, we have three options in a submenu of a file menu.

imp = JMenu.new "Import"
...
fileMenu.add imp

A submenu is just like any other normal menu. It is created the same way. We simply add a menu to existing menu.

fileExit.setAccelerator KeyStroke.getKeyStroke KeyEvent::VK_W,
      ActionEvent::CTRL_MASK

An accelerator is a key shortcut that launches a menu item. In our case, by pressing Ctrl+W we close the application.

fileMenu.addSeparator

A separator is a horizontal line that visually separates the menu items. This way we can group items into some logical places.

Figure: Submenu

Popup menu

In the next example, we create a popup menu.

#!/usr/local/bin/jruby

# ZetCode JRuby Swing tutorial
#
# This program creates a 
# popup menu.
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: December 2010


include Java

import java.awt.event.MouseAdapter
import javax.swing.JFrame
import javax.swing.JPopupMenu
import javax.swing.JMenuItem
import java.lang.System


class MouseAction < MouseAdapter
  
  def mouseReleased e
    source = e.source
    menu = source.getMenu
    
    if e.getButton == e.button
      menu.show e.getComponent, e.getX, e.getY
    end
  end  
end  

class Example < JFrame
  
  def initialize
    super "Popup menu"
    
    self.initUI
  end
    
  def initUI
    
    @menu = JPopupMenu.new
    menuItemBeep = JMenuItem.new "Beep" 
    menuItemBeep.addActionListener do |e|
      toolkit = getToolkit
      toolkit.beep        
    end
    @menu.add menuItemBeep

    menuItemExit = JMenuItem.new "Exit" 
    menuItemExit.addActionListener do |e|
      System.exit 0  
    end 
    
    @menu.add menuItemExit
    self.addMouseListener MouseAction.new
    
    self.setDefaultCloseOperation JFrame::EXIT_ON_CLOSE
    self.setSize 250, 200
    self.setLocationRelativeTo nil
    self.setVisible true
  end
  
  def getMenu
    @menu
  end  
end

Example.new

In our example, we create a popup menu with two menu items.

@menu = JPopupMenu.new
menuItemBeep = JMenuItem.new "Beep"

We create a popup menu and a menu item.

self.addMouseListener MouseAction.new

We add a mouse listener to the Example class. The mouse listener is a MouseAction user defined class, which inherits from a MouseAdapter . It is a convenience class which implements all five required methods. The methods are empty. Instead of implementing all five methods, we implement only the methods that we need.

class MouseAction < MouseAdapter
  
  def mouseReleased e
...

In our MouseAction class we implement the mouseReleased method.

if e.getButton == e.button:
  menu.show e.getComponent, e.getX, e.getY
end

We show the popup menu window at the x, y coordinates of the mouse click.

Figure: Popup menu

JToolbar

Menus group commands that we can use in an application. Toolbars provide a quick access to the most frequently used commands. In Swing, the JToolBar class creates a toolbar in an application.

#!/usr/local/bin/jruby


# ZetCode JRuby Swing tutorial
#
# This program creates a 
# toolbar.
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: December 2010


include Java

import java.awt.BorderLayout
import javax.swing.JFrame
import javax.swing.ImageIcon
import javax.swing.JButton
import javax.swing.JMenuBar
import javax.swing.JMenu
import javax.swing.JToolBar
import java.lang.System



class Example < JFrame
  
  def initialize
    super "Toolbar"
    
    self.initUI
  end
    
  def initUI
    
    menubar = JMenuBar.new
    fileMenu = JMenu.new "File"
    menubar.add fileMenu

    toolbar = JToolBar.new

    iconExit = ImageIcon.new "exit2.png"

    exitButton = JButton.new iconExit
    exitButton.addActionListener do |e|
      System.exit 0  
    end
    
    toolbar.add exitButton

    self.add toolbar, BorderLayout::NORTH

    self.setJMenuBar menubar
    
    self.setDefaultCloseOperation JFrame::EXIT_ON_CLOSE
    self.setSize 350, 250
    self.setLocationRelativeTo nil
    self.setVisible true
  end     
end

Example.new

The example creates a toolbar with one exit button.

toolbar = JToolBar.new

A toolbar is created.

exitButton = JButton.new iconExit
...
toolbar.add exitButton

We create a button and add it to the toolbar.

self.add toolbar, BorderLayout::NORTH

The toolbar is placed into the north part of the BorderLayout manager. The BorderLayout manager is the default layout manager for the JFrame container.

Figure: Toolbar

In this part of the JRuby Swing tutorial, we mentioned menus and toolbars.