How to use a scala.swing.Applet in a Scala Swing application?

I try to port some Java code to Scala.

I want to display a scala.swing.Applet in a GUI application.

With Java Swing I would do

val jframe = new JFrame()
jframe.add(APPLET)

jframe.setVisible(true)
APPLET.setFocusCycleRoot(true)

APPLET.开发者_StackOverflow中文版init()
APPLET.start()

But code using Scala Swing

def top = new MainFrame {
  contents = APPLET
}

doesn't like the type:

error: type mismatch;
found   : scala.swing.Applet
required: scala.swing.Component
contents = APPLET

When I try to add the Applet via the Java peers, it fails like this:

def top = new MainFrame {
  contents = new Panel() {
    peer.add(new SinglePlayerGame)
  }
}

I get this error message:

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: scala.swing.Applet cannot be cast to javax.swing.JComponent
    at scala.swing.Container$Wrapper$$anon$1.componentAdded(Container.scala:43)
    at java.awt.Container.processContainerEvent(Container.java:2071)
    at java.awt.Container.processEvent(Container.java:2042)
    at java.awt.Component.dispatchEventImpl(Component.java:4629)
    at java.awt.Container.dispatchEventImpl(Container.java:2103)
    at java.awt.Component.dispatchEvent(Component.java:4455)
    at java.awt.Container.addImpl(Container.java:1081)
    at java.awt.Container.add(Container.java:373)

How am I supposed to solve that problem?

It's not written in Scala, but Subway is a simple example of a hybrid applet and application. Both JApplet and JFrame are top-level containers, and initContainer() performs the common initialization.

Note that both components require proper attention to Initial Threads.