Help, on calling another frame

Question

I am doing a program which start with a frame. Where is a button, by clicking it, another window may popup to show some running msg of the main window. I decide to use two frames to do that. One is the main window and another one will be visible when that button is clicked. Now my problem is the second window(frame) did come up, but the JTextArea inside it is not been displayed. There is one time that the second window displayed its content when some process in main window throws exceptions. I have no idea what I did wrong.
second window:
public class networkConnect extends JFrame {
    public JLabel msgLbl;
    public JTextArea msgArea;
    public networkConnect()
        Toolkit kit = Toolkit.getDefaultToolkit();
        Dimension screenSize = kit.getScreenSize();
        int screenHeight = screenSize.height;
        int screenWidth = screenSize.width;
        msgLbl = new JLabel();
        this.msgArea = new JTextArea(30,50);
        this.msgArea.setEditable(false);
        this.getContentPane().add("Center", new JScrollPane(msgArea));
        this.setTitle("Connection Message");
        this.setSize(150,70);
        this.setLocation(screenWidth/4,screenHeight/4);
        this.pack();
        this.show();
}In main window:
networkConnect netConnect = new networkConnect();
netConnect.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
netConnect.setVisible(true);
netConnect.......Thank you!!

Answer 1

for instance:
import java.awt.*;
import javax.swing.*;
public class NetWorkConnect
  private static final Dimension PANEL_SIZE = new Dimension(250, 170);
  private JPanel mainPanel = new JPanel();
  private JTextArea msgArea = new JTextArea(30, 50);
  public NetWorkConnect()
    msgArea.setEditable(false);
    mainPanel.setPreferredSize(PANEL_SIZE);
    mainPanel.setLayout(new BorderLayout());
    mainPanel.add(new JScrollPane(msgArea), BorderLayout.CENTER);
  public JComponent getComponent()
    return mainPanel;
  public void appendMessage(String message)
    msgArea.append(message);
  public void clearMsgArea()
    msgArea.setText("");
import java.awt.*;
import java.awt.Dialog.*;
import java.awt.event.*;
import javax.swing.*;
public class NetWorkConnectMain
  private JPanel mainPanel = new JPanel();
  private JTextField textfield = new JTextField(20);
  private NetWorkConnect netConnect = new NetWorkConnect();
  private JDialog dialog;
  private JButton appendTextBtn;
  public NetWorkConnectMain()
    JButton showNetConnectBtn = new JButton("Show NetConnect");
    appendTextBtn = new JButton("Append Text to NetConnect");
    textfield.setEnabled(false);
    appendTextBtn.setEnabled(false);
    showNetConnectBtn.addActionListener(new ActionListener()
      public void actionPerformed(ActionEvent arg0)
        showNetConnectAction();
    appendTextBtn.addActionListener(new ActionListener()
      public void actionPerformed(ActionEvent arg0)
        appendTextAction();
    mainPanel.add(showNetConnectBtn);
    mainPanel.add(textfield);
    mainPanel.add(appendTextBtn);
  private void showNetConnectAction()
    if (dialog == null)
      Window windowAncestor = SwingUtilities.getWindowAncestor(mainPanel);
      dialog = new JDialog(windowAncestor, "Connection Message", ModalityType.MODELESS);
      dialog.getContentPane().add(netConnect.getComponent());
      dialog.pack();
      dialog.setLocationRelativeTo(null);
      dialog.setVisible(true);
    else if (!dialog.isVisible())
      dialog.setVisible(true);
    appendTextBtn.setEnabled(true);
    textfield.setEnabled(true);
  public void appendTextAction()
    if (dialog != null && netConnect != null)
      netConnect.appendMessage(textfield.getText() + "\n");
  public JComponent getComponent()
    return mainPanel;
  private static void createAndShowUI()
    JFrame frame = new JFrame("NetWork Connect Main");
    frame.getContentPane().add(new NetWorkConnectMain().getComponent());
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
  public static void main(String[] args)
    java.awt.EventQueue.invokeLater(new Runnable()
      public void run()
        createAndShowUI();
}