Introduction to JRuby Swing
In this part of the JRuby Swing tutorial, we will introduce the Swing toolkit and create our first programs using the JRuby programming language.
The purpose of this tutorial is to get you started with the Swing toolkit with the JRuby language. Images used in this tutorial can be downloaded here. I used some icons from the Tango icons pack of the Gnome project.
Swing library is an official Java GUI toolkit for the Java programming language. It is used to create Graphical user interfaces with Java. Swing is an advanced GUI toolkit. It has a rich set of components. From basic ones like buttons, labels, scrollbars to advanced components like trees and tables. Swing itself is written in Java. Swing is available for other languages too. For example JRuby, Jython, Groovy, or Scala.
JRuby is a Java implementation of the Ruby programming language. JRuby can import any Java class.
There are two basic ways to execute the examples in this tutorial. One way is to install a Ruby NetBeans plugin. It contains JRuby as well. When you create a new Ruby project, be sure to select the JRuby platform.
The other way is to download a release from the jruby.org website.
$ tar -xzvf jruby-bin-1.5.6.tar.gz $ mv jruby-1.5.6/ ~/bin
Installing JRuby is very easy. We extract the contents of the compressed archive and move the directory to a selected location. On my system, I have moved the directory to the bin directory of my home directory.
$ ~/bin/jdk1.6.0_21/bin/java -jar ~/bin/jruby-1.5.6/lib/jruby.jar simple.rb
We have installed JRuby in a selected directory. In the
we will find
jruby.jar file, which is used to execute JRuby scripts.
$ cat /usr/local/bin/jruby #!/bin/bash ~/bin/jdk1.6.0_21/bin/java -jar ~/bin/jruby-1.5.6/lib/jruby.jar $1
Optionally, we can create a bash file which will automatically start our JRuby
scripts. We can then put the
#!/usr/local/bin/jruby path to our scripts.
In our first example, we will show a basic window on the screen.
#!/usr/local/bin/jruby # ZetCode JRuby Swing tutorial # # This example shows a simple # window in the center of the screen. # # author: Jan Bodnar # website: www.zetcode.com # last modified: December 2010 include Java import javax.swing.JFrame class Example < JFrame def initialize super "Simple" self.initUI end def initUI self.setSize 300, 200 self.setDefaultCloseOperation JFrame::EXIT_ON_CLOSE self.setLocationRelativeTo nil self.setVisible true end end Example.new
While this code is very small, the application window can do quite a lot. It can be resized, maximised, minimised. All the complexity that comes with it has been hidden from the application programmer.
We include Java API to JRuby.
We import a
JFrame class. The
JFrame is a top-level
window with a titlebar and a border.
We delegate the creation of the user interface to the
self.setSize 300, 200
We set the size of the window.
This method ensures that the window terminates if we click on the close button of the titlebar. By default nothing happens.
We center the window on the screen.
Finally, the window is showed on the screen.
A tooltip is a small rectangular window, which gives a brief information about an object. It is usually a GUI component. It is part of the help system of the application.
#!/usr/local/bin/jruby # ZetCode JRuby Swing tutorial # # This code shows a tooltip on # a window and a button # # author: Jan Bodnar # website: www.zetcode.com # last modified: December 2010 include Java import javax.swing.JButton import javax.swing.JFrame import javax.swing.JPanel class Example < JFrame def initialize super "Tooltips" self.initUI end def initUI panel = JPanel.new self.getContentPane.add panel panel.setLayout nil panel.setToolTipText "A Panel container" button = JButton.new "Button" button.setBounds 100, 60, 100, 30 button.setToolTipText "A button component" panel.add button self.setDefaultCloseOperation JFrame::EXIT_ON_CLOSE self.setSize 300, 200 self.setLocationRelativeTo nil self.setVisible true end end Example.new
In the example, we set the tooltip for the frame and the button.
panel = JPanel.new self.getContentPane.add panel
We create a
JPanel component. It is a generic lightweight
JFrame has an area, where you put the components
called the content pane. We put the panel into this pane.
By default, the
JPanel has a
FlowLayout manager. The layout
manager is used to place widgets onto the containers. If we call
we can position our components absolutely. For this, we use the
panel.setToolTipText "A Panel container"
To enable a tooltip, we call the
In the last example of this section, we will create a quit button. When we press this button, the application terminates.
#!/usr/local/bin/jruby # ZetCode JRuby Swing tutorial # # This program creates a quit # button. When we press the button, # the application terminates. # # author: Jan Bodnar # website: www.zetcode.com # last modified: December 2010 include Java import javax.swing.JButton import javax.swing.JFrame import javax.swing.JPanel import java.lang.System class Example < JFrame def initialize super "Quit button" self.initUI end def initUI panel = JPanel.new self.getContentPane.add panel panel.setLayout nil qbutton = JButton.new "Quit" qbutton.setBounds 50, 60, 80, 30 qbutton.add_action_listener do |e| System.exit 0 end panel.add qbutton self.setDefaultCloseOperation JFrame::EXIT_ON_CLOSE self.setSize 300, 200 self.setLocationRelativeTo nil self.setVisible true end end Example.new
We position a
JButton on the window. We will add an action listener
to this button.
qbutton = JButton.new "Quit" qbutton.setBounds 50, 60, 80, 30
Here we create a button. We position it by calling the
qbutton.add_action_listener do |e| System.exit 0 end
We add an action listener to the button. The listener terminates the application.
This section was an introduction to the Swing toolkit with the JRuby language.