Scala example source code file (LinePainting.scala)

This example Scala source code file (LinePainting.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

awt, color, focuslost, line, linepainting, mainframe, mousedragged, mousepressed, mousepressed, mousereleased, panel, point, point, press, press

The Scala LinePainting.scala source code

package scala.swing
package test
import scala.swing.Swing._
import scala.swing.{MainFrame, Panel, SimpleGUIApplication}
import scala.swing.event._
import java.awt.{Color, Dimension, Graphics, Graphics2D, Point, geom}

/**
 * Dragging the mouse draws a simple graph
 * 
 * @author Frank Teubler, Ingo Maier
 */
object LinePainting extends SimpleSwingApplication {
  lazy val ui = new Panel {
    background = Color.white
    preferredSize = (200,200)

    focusable = true
    listenTo(mouse.clicks, mouse.moves, keys)
    
    reactions += {
      case e: MousePressed  => 
        moveTo(e.point)
        requestFocusInWindow()
      case e: MouseDragged  => lineTo(e.point)
      case e: MouseReleased => lineTo(e.point)
      case KeyTyped(_,'c',_,_) => 
        path = new geom.GeneralPath
        repaint()
      case _: FocusLost => repaint()
    }

    /* records the dragging */
    var path = new geom.GeneralPath

    def lineTo(p: Point) { path.lineTo(p.x, p.y); repaint() }
    def moveTo(p: Point) { path.moveTo(p.x, p.y); repaint() }

    override def paintComponent(g: Graphics2D) = {
      super.paintComponent(g)
      g.setColor(new Color(100,100,100))
      g.drawString("Press left mouse button and drag to paint." + 
                   (if(hasFocus) " Press 'c' to clear." else ""), 10, size.height-10)
      g.setColor(Color.black)
      g.draw(path)
    }
  }
  
  def top = new MainFrame {
    title = "Simple Line Painting Demo"
    contents = ui
  }
}