Swing Scala Question - 100% expansion of panel

Even though the code is scala, you can see the swing oriented approach. I just want to add a text area to a panel(core) and associate panel(core) with the frame. I want panel core and the text area to fill out 100% in the width and the height. Basically, I just want a text area shown. With this code, I can sort of see the textfield but is it. The width looks like it is only 1 pixel.

Possible Solution? should I find a way to add a layout to the frame? Which layout?

import java.awt.{ Insets, GridBagConstraints, Dimension }
import javax.swing.{ JPanel, JScrollPane, JTextArea }
import scala.swing.Swing._
import scala.swing.{ MainFrame, Panel, SimpleSwingApplication }

object LogAnaylyzerMain extends SimpleSwingApplication {

  def maxWidth = 900
  def maxHeight = 600
  def initXPos = 320
  def initYPos = 260

  /**
   * Core Panel Content.
   */
  object coreContentPanel extends JPanel {

    val outputTextArea = new JTextArea
    val outputTextScrollPane = new JScrollPane(outputTextArea)
    this.add(outputTextScrollPane)
  }

  class outputTextArea extends JTextArea {
    this.setLineWrap(false)
    this.setCaretPosition(0)
    this.setEditable(true);
  }

  /**
   * Main Frame, entry point.
   */
  def top = new MainFrame {
    peer.setLocation(initXPos, initYPos)
    title = "JVM Log Analyzer"
    contents = new Panel {
      preferredSize = (maxWidth, maxHeight)
      focusable = true
      peer.add(c开发者_如何学运维oreContentPanel)
      pack()
    }
  }

} // End of the Class //

The default layout of JPanel (and Panel) is FlowLayout. Using GridLayout or BorderLayout center should let the JTextArea fill the preferred size.

Addendum: Here's a (somewhat) comparable Java Swing example:

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;

/** @see http://stackoverflow.com/questions/5421319 */
public class TextAreaTest extends JPanel {

    private static final int maxWidth = 900;
    private static final int maxHeight = 600;
    private static final int initXPos = 320;
    private static final int initYPos = 260;
    private JTextArea ta = new JTextArea();

    public TextAreaTest() {
        this.setPreferredSize(new Dimension(900, 600));
        this.setLayout(new GridLayout());
        this.add(ta);
        ta.append("Hello, world!");
    }

    private void display() {
        JFrame f = new JFrame("TextAreaTest");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(this);
        f.pack();
        f.setLocation(initXPos, initYPos);
        f.setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new TextAreaTest().display();
            }
        });
    }
}