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 
.
.
.
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(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.