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32 GUI Programming

32.1 A first Swing application

  import scala.swing._


// In file swing/FirstSwingApp.scala

  import scala.swing._

  object FirstSwingApp extends SimpleGUIApplication {
    def top = new MainFrame {
      title = "First Swing App"
      contents = new Button {
        text = "Click me"
      }
    }
  }


  object FirstSwingApp extends SimpleGUIApplication {


    def top = new MainFrame {


      title = "First Swing App"


  def title: String


  def title_=(s: String)


      contents = new Button {


        text = "Click me"


  

32.2 Panels and layouts

// In file swing/SecondSwingApp.scala

import scala.swing._

object SecondSwingApp extends SimpleGUIApplication {
  def top = new MainFrame {
    title = "Second Swing App"
    val button = new Button {
      text = "Click me"
    }
    val label = new Label {
      text = "No button clicks registered"
    }	
    contents = new BoxPanel(Orientation.Vertical) {
      contents += button
      contents += label
      border = Swing.EmptyBorder(30, 30, 10, 30)
    }
  }
}  


  val label = new Label {
    text = "No button clicks registered"
  }	


  contents = new BoxPanel(Orientation.Vertical) {


  contents += button
  contents += label


  border = Swing.EmptyBorder(30, 30, 10, 30)


  

32.3 Handling events

  listenTo(button)


  case class ButtonClicked(source: Button)


  var nClicks = 0
  reactions += {
    case ButtonClicked(b) =>
      nClicks += 1
      label.text = "Number of button clicks: "+ nClicks
  }


// In file swing/ReactiveSwingApp.scala

import scala.swing._
import scala.swing.event._

object ReactiveSwingApp extends SimpleGUIApplication {
  def top = new MainFrame {
    title = "Reactive Swing App"
    val button = new Button {
      text = "Click me"
    }
    val label = new Label {
      text = "No button clicks registered"
    }	
    contents = new BoxPanel(Orientation.Vertical) {
      contents += button
      contents += label
      border = Swing.EmptyBorder(30, 30, 10, 30)
    }
    listenTo(button)
    var nClicks = 0
    reactions += {
      case ButtonClicked(b) =>
        nClicks += 1
        label.text = "Number of button clicks: "+ nClicks
    }
  }
}  


// In file swing/TempConverter.scala

import swing._
import event._

object TempConverter extends SimpleGUIApplication {
  def top = new MainFrame {
    title = "Celsius/Fahrenheit Converter"
    object celsius extends TextField { columns = 5 }
    object fahrenheit extends TextField { columns = 5 }
    contents = new FlowPanel {
      contents += celsius
      contents += new Label(" Celsius  =  ")
      contents += fahrenheit
      contents += new Label(" Fahrenheit")
      border = Swing.EmptyBorder(15, 10, 10, 10)
    }
    listenTo(celsius, fahrenheit)
    reactions += {
      case EditDone(`fahrenheit`) =>
        val f = fahrenheit.text.toInt
        val c = (f - 32) * 5 / 9
        celsius.text = c.toString
      case EditDone(`celsius`) =>
        val c = celsius.text.toInt
        val f = c * 9 / 5 + 32
        fahrenheit.text = f.toString
    }     
  }
}


  

32.4 Example: Celsius/Fahrenheit converter

  import swing._
  import event._


  import scala.swing._
  import scala.swing.event._


   case EditDone(`celsius`)


  

32.5 Conclusion