How to translate the use of Java internal classes in JRuby code - jruby

Question

I am trying to play with JRuby with Java Swing : taking examples here and there, I am trying to translate them from pure Java to JRuby. That works well, especially after reading the part dedicated to Jruby in the excellent site Zetcode.
However there are things I still don't know how to translate.
For instance, picking this java code from Horstmann book, how could I translate correctly into JRuby ? In this code (in the Jpanel constructor), we rely on internal class for MouseAdapter. The rest is easy.
How to translate such internal (or more adequately 'anonymous') classes ?

Answer 1

just refactor/adjust parts to work out for you e.g.
frame = javax.swing.JFrame.new
frame.title = "MouseTest"
frame.set_size(300, 200)
frame.add_window_listener do |evt|
if evt.getID == java.awt.event.WindowEvent::WINDOW_CLOSING
java.lang.System.exit(0)
end
end
class MousePanel < Java::JavaxSwing::JPanel
SQUARELENGTH = 10; MAXNSQUARES = 100;
def initialize
super
#squares = []; #current = nil
add_mouse_listener self
add_mouse_motion_listener self
end
def add(x, y)
if #squares.size < MAXNSQUARES
#current = #squares.size
#squares << Point.new(x, y)
repaint
end
end
def remove(n)
return if (n < 0 || n >= #squares.size)
#squares.pop
#squares[n] = #squares[#squares.size];
#current = nil if #current == n
repaint
end
def paintComponent(graphics)
super
#squares.each { |square| do_draw(graphics, square) }
end
def do_draw(graphics, square)
graphics.drawRect(
square.x - SQUARELENGTH / 2,
square.y - SQUARELENGTH / 2,
SQUARELENGTH, SQUARELENGTH
)
end
private :do_draw
include java.awt.event.MouseListener
[ 'mouseEntered', 'mouseExited', 'mouseReleased' ].each do |method|
class_eval "def #{method}(evt); end"
end
def mousePressed(evt)
puts "mousePressed #{evt}"
end
def mouseClicked(evt)
puts "mouseClicked #{evt}"
end
include java.awt.event.MouseMotionListener
def mouseMoved(evt)
puts "mouseMoved #{evt}"
end
def mouseDragged(evt)
puts "mouseDragged #{evt}"
end
end
frame.content_pane.add MousePanel.new
frame.show
NOTE all the updated *add_xxx_listener occurrences ...
put this into a gist for readability/forkability (including the original code) : https://gist.github.com/kares/8538048