Writing own key publisher for MainFrame

I want my MainFrame to catch key events. I didn't find any key publisher already in it, so I'm going to write my own ... I have something like this:

class ImageView(image: ImageIcon, parent: U开发者_开发百科IElement = null) extends MainFrame {

  object keys extends Publisher {
    peer.addKeyListener(new KeyListener {
      def keyPressed(e: java.awt.event.KeyEvent) {
        publish(new KeyPressed(e))
      }

      def keyReleased(e: java.awt.event.KeyEvent) {
        publish(new KeyReleased(e))
      }

      def keyTyped(e: java.awt.event.KeyEvent) {
        publish(new KeyTyped(e))
      }
    })
  }

  listenTo(keys)

  reactions += {
     case KeyPressed(_, key,_,_) =>
       if (key == Key.Escape) dispose
  }

}

Anyway when I press any key, I get this exception:

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: scala.swing.Frame$$anon$1 cannot be cast to javax.swing.JComponent
    at scala.swing.event.KeyPressed.<init>(KeyEvent.scala:33)
    at pip.gui.ImageView$keys$$anon$2.keyPressed(ImageView.scala:35)
    at java.awt.Component.processKeyEvent(Component.java:6225)
    at java.awt.Component.processEvent(Component.java:6044)
    at java.awt.Container.processEvent(Container.java:2041)
    at java.awt.Window.processEvent(Window.java:1836)
    at java.awt.Component.dispatchEventImpl(Component.java:4630)
    at java.awt.Container.dispatchEventImpl(Container.java:2099)
    at java.awt.Window.dispatchEventImpl(Window.java:2478)
    at java.awt.Component.dispatchEvent(Component.java:4460)
    at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1850)
    at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:712)
    at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:990)
    at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:855)
    at 
.
.
.
.
(continues long further)

I brought up this publisher code from Component.keys, so what is actually wrong here?

Thanks in advance, Tony

---

This seems bad design in the library. Looking into KeyEvent.scala, there's all kinds of casting to JComponent going on, and JFrame is a subclass of java.awt.Component but not JComponent, so it should be impossible to call listenTo(keys).

What you want is to listen to the top-most component in the frame's contents. For instance:

import scala.swing._; import event._
import javax.swing._

class ImageView(image: ImageIcon, parent: UIElement = null) extends MainFrame {
   val b = new BorderPanel {
      listenTo( keys )
      reactions += {
         case KeyPressed(_, key,_,_) =>
            println( "PRESSED : " + key )
            if (key == Key.Escape) dispose
      }
   }
   contents = b
}

val w = new ImageView( null )
w.peer.setSize( 200, 200 )
w.visible = true
w.b.requestFocus

the requestFocus is essential because the panel doesn't request the focus by itself even if you click on it, so otherwise it wouldn't receive key events.