How to interrupt the window closing mechanism in scala swing

Question

I'm building a GUI with the SimpleSwingApplication trait in scala swing. What I want to do is to provide a mechanism on close, that asks the user (Yes,No,Cancel) if he didn't save the document yet. If the user hits Cancel the Application shouldn't close. But everything I tried so far with MainFrame.close and closeOperation didn't work.

So how is this done in Scala Swing?

I'm on Scala 2.9.

Thanks in advance.

Mnemosyne

Answer 1

Slightly different variation from what Howard suggested

import scala.swing._

object GUI extends SimpleGUIApplication {
  def top = new Frame {
    title="Test"

    import javax.swing.WindowConstants.DO_NOTHING_ON_CLOSE
    peer.setDefaultCloseOperation(DO_NOTHING_ON_CLOSE)

    override def closeOperation() { showCloseDialog() }

    private def showCloseDialog() {
      Dialog.showConfirmation(parent = null,
        title = "Exit",
        message = "Are you sure you want to quit?"
      ) match {
        case Dialog.Result.Ok => exit(0)
        case _ => ()
      }
    }
  }
}

By using DO_NOTHING_ON_CLOSE you are given a chance to define what should be done when a WindowEvent.WINDOW_CLOSING event is received by the scala frame. When a scala frame receives a WINDOW_CLOSING event it reacts by calling closeOperation. Hence, to display a dialog when the user attempts to close the frame it is enough to override closeOperation and implement the desired behavior.

Dawdle

Thank you. After removing the deprecations, this did the trick. – Mnemosyne

Answer 2

What about this:

import swing._
import Dialog._

object Test extends SimpleSwingApplication { 
  def top = new MainFrame { 
    contents = new Button("Hi")

    override def closeOperation { 
      visible = true
      if(showConfirmation(message = "exit?") == Result.Ok) super.closeOperation  
    }
  }
}

Oldtime

Unfortunately this doesn't work (at least not when it is a MainFrame), because the confirmation dialog only appears after the main window has already disappeared. – Larrylars

Answer 3

I am not really familiar with scala swing but I found this code in some of my old test programs:

object GUI extends SimpleGUIApplication {
  def top = new Frame {
    title="Test"
    peer.setDefaultCloseOperation(0)

    reactions += {
      case WindowClosing(_) => {
        println("Closing it?")
        val r = JOptionPane.showConfirmDialog(null, "Exit?")
        if (r == 0) sys.exit(0)
      }
    }
  }
}

Sizar

I am not sure: is sys.exit(0) normal for this purpose? At first sight it seems too heavy, but I may be wrong. – Alyciaalyda

Answer 4

This does what I wanted to do; calling super.closeOperation didn't close the frame. I would have just said that in a comment, but I am not yet allowed.

object FrameCloseStarter extends App {
  val mainWindow = new MainWindow()
  mainWindow.main(args)
}

class MainWindow extends SimpleSwingApplication {
  def top = new MainFrame {
    title = "MainFrame"
    preferredSize = new Dimension(500, 500)
    pack()
    open()

    def frame = new Frame {
      title = "Frame"
      preferredSize = new Dimension(500, 500)
      location = new Point(500,500)
      pack()

      peer.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE)

      override def closeOperation() = {
        println("Closing")
        if (Dialog.showConfirmation(message = "exit?") == Result.Ok) {
          peer.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE)
          close()
        }
      }
    }
    frame.open()
  }
}

Hipolitohipp