Swing progress bar demo in JRuby

jruby_progress_bar_demo.rb

# Program translate from 
# http://download.oracle.com/javase/tutorial/uiswing/examples/components/ProgressBarDemoProject/src/components/ProgressBarDemo.java
# 2011/08/01 first commit (by Mason)
require "java"

java_import java.awt::Toolkit
java_import java.awt::Cursor
java_import java.awt::Insets
java_import java.awt::BorderLayout
java_import javax.swing::JFrame
java_import javax.swing::JPanel
java_import javax.swing::SwingWorker
java_import javax.swing::JScrollPane
java_import javax.swing::JProgressBar
java_import javax.swing::BorderFactory

class Task < SwingWorker
  def initialize(program, start_button, task_output)
    super()
    @program = program
    @start_button = start_button
    @task_output = task_output
  end

  def doInBackground
    progress = 0
    set_progress(0)
    while progress < 100
      progress += rand(10)
      sleep(rand)
      set_progress([progress, 100].min)
    end
    return
  end
  
  def done
    Toolkit.get_default_toolkit.beep
    @start_button.set_enabled(true)
    @program.set_cursor(nil) #turn off the wait cursor
    @task_output.append("Done!\n")
  end
end  

class ProgressBarDemo < JPanel
  def self.create_and_show_gui
    # Create and set up the window.
    frame = JFrame.new("ProgressBarDemo")
    frame.set_default_close_operation(JFrame::EXIT_ON_CLOSE)

    # Create and set up the content pane.
    new_content_pane = ProgressBarDemo.new
    new_content_pane.set_opaque(true) # content panes must be opaque
    frame.set_content_pane(new_content_pane)

    # Display the window.
    frame.pack
    frame.set_visible(true)
  end

  def initialize
    super(BorderLayout.new)
    
    # Create the demo's UI.
    @start_button = javax.swing::JButton.new("Start")
    @start_button.set_action_command("start")
    @start_button.add_action_listener do |evt1|
      @start_button.set_enabled(false)
      self.set_cursor(Cursor.get_predefined_cursor(Cursor::WAIT_CURSOR))
      # Instances of javax.swing.SwingWorker are not reusuable, so
      # we create new instances as needed.
      task = Task.new(self, @start_button, @task_output)
      task.add_property_change_listener do |evt2|
        if "progress" == evt2.get_property_name
          progress = evt2.get_new_value.to_i
          @progress_bar.set_value(progress)
          @task_output.append("Completed #{progress}% of task.\n");
        end
      end
      task.execute
    end
    
    @task_output = javax.swing::JTextArea.new(5, 20)
    @task_output.set_margin(Insets.new(5,5,5,5))
    @task_output.set_editable(false)
    
    @progress_bar = JProgressBar.new(0, 100)
    @progress_bar.set_value(0)
    @progress_bar.set_string_painted(true)
    
    @panel = javax.swing::JPanel.new
    @panel.add(@start_button)
    @panel.add(@progress_bar)

    add(@panel, BorderLayout::PAGE_START);
    add(JScrollPane.new(@task_output), BorderLayout::CENTER)
    setBorder(BorderFactory.create_empty_border(20, 20, 20, 20))
  end
end

javax.swing::SwingUtilities.invoke_later do
  ProgressBarDemo.create_and_show_gui
end