Grid Pane from http://docs.oracle.com/javafx/2/get_started/form.htm#BABHABBF in jrubyfx

form_javafx.rb

require 'java'
require 'jrubyfx'

JavaFX = Java::javafx

class FormApp < JRubyFX::Application
  def start(stage)
    stage.set_title("JavaFX Welcome")

    grid = JavaFX::scene.layout.GridPane.new
    grid.alignment = JavaFX.geometry.Pos::CENTER
    grid.hgap = 10
    grid.vgap = 10
    grid.padding = JavaFX.geometry.Insets.new(25, 25, 25, 25)

    scenetitle = JavaFX.scene.text.Text.new("Welcome")
    scenetitle.font = JavaFX.scene.text.Font.font("Tahoma",
                           JavaFX.scene.text.FontWeight::NORMAL, 20)
    grid.add(scenetitle, 0, 0, 2, 1)

    user_name = JavaFX.scene.control.Label.new("User Name:")
    grid.add(user_name, 0, 1)

    user_text_field = JavaFX.scene.control.TextField.new
    grid.add(user_text_field, 1, 1)

    pw = JavaFX::scene::control::Label.new("Password:")
    grid.add(pw, 0, 2)

    pw_box = JavaFX::scene::control::PasswordField.new
    grid.add(pw_box, 1, 2)

    # for debugging: shows spaces between added Controls
    grid.grid_lines_visible = true
    
    button = JavaFX::scene::control::Button.new("Sign in")
    hbox_button = JavaFX::scene::layout::HBox.new(10)
    hbox_button.alignment = JavaFX::geometry::Pos::BOTTOM_RIGHT
    hbox_button.children.add(button)
    grid.add(hbox_button, 1, 4)

    actiontarget = JavaFX::scene::text::Text.new
    grid.add(actiontarget, 1, 6)

    button.set_on_action do
      #puts "foo"
      actiontarget.fill = JavaFX::scene::paint::Color::FIREBRICK
      actiongarget.text = "Sign in button pressed"
    end

    scene = JavaFX.scene.Scene.new(grid, 300, 275)
    stage.scene = scene
    
    stage.show
  end
end

FormApp.launch