In the program below, the JTextField never gets focus. It is impossible to get focus to it by clicking on it, or by hitting TAB, or in any other way that I know of.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

public class FocusTest extends JFrame
{
  JScrollPane workPane;
  static PSearch panel0, panel1;
  JSplitPane split_V1;
  JPanel emptyPane;
  
  public FocusTest() {
    super("Focus Test");
    
    workPane=new JScrollPane();
    panel0=new PSearch();
    
    emptyPane=new JPanel();
    JLabel lblEmpty=new JLabel("Empty Pane");
    lblEmpty.setFont(new Font("SansSerif",Font.BOLD,18));
    emptyPane.add(lblEmpty);
    
    split_V1=new JSplitPane(JSplitPane.VERTICAL_SPLIT, panel0,emptyPane);
    
    getContentPane().add(split_V1, BorderLayout.CENTER);
    
    setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
    addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
if (JOptionPane.showConfirmDialog(null,
"Do you really want to exit?", "Focus Test",
JOptionPane.OK_CANCEL_OPTION)==JOptionPane.OK_OPTION) {

            System.exit(0);
}
      }
      /* public void windowActivated(WindowEvent we) {
FocusTest.panel0.txtSearch.requestFocus();
      }
      public void windowOpened(WindowEvent we) {
FocusTest.panel0.txtSearch.requestFocus();
      } */
    });
    
  }

  public static void main(String s[]) {
    FocusTest window = new FocusTest();
    window.setSize(450, 450);
    window.setVisible(true);
  }


  protected class PSearch extends JPanel implements ActionListener {
    protected JTextField txtSearch=new JTextField(10);
    protected JLabel lblSearch=new JLabel("Enter search string: ");
    protected JButton btnSearch=new JButton("Search");
    
    public PSearch() {
      btnSearch.setActionCommand("Search");
      btnSearch.setMnemonic(KeyEvent.VK_S);
      lblSearch.setLabelFor(btnSearch);
      btnSearch.addActionListener(this);

      txtSearch.setActionCommand("Search");
      txtSearch.addActionListener(this);

      txtSearch.addFocusListener(new FocusAdapter(){
public void focusGained(FocusEvent e){
txtSearch.selectAll();
}
      });

      //Layout the components
      add(lblSearch);
      add(txtSearch);
      add(btnSearch);
    }

    public void actionPerformed(ActionEvent e){
      String cmd=e.getActionCommand();
      if(cmd.equals("Search") && FocusTest.panel1==null) {
this.txtSearch.requestFocus();
DlgException ex=new DlgException("This is a test message!");
if (ex.show()==JOptionPane.YES_OPTION) {
//Do something here, then show another messagebox or dialog.
ex=new DlgException("Another message...");
ex.show();
//Disable the components in panel0 does not help.
//for(int i=0;i<this.getComponentCount ();i++)
// this.getComponent(i).setEnabled (false);

FocusTest.panel1=new PSearch();
split_V1.setBottomComponent(FocusTest.panel1);
split_V1.repaint();

FocusTest.panel1.txtSearch.requestFocus();
}
      }
    }
  }

  protected class DlgException {
    private String msg=null;
    private String[] options={"Override",
"Cancel"};
    
    public DlgException(String msg) {
      this.msg =msg;
    }

    public int show(){
      return JOptionPane.showOptionDialog(null,
msg,
"Exception message",
JOptionPane.YES_NO_OPTION,
JOptionPane.WARNING_MESSAGE,
null,
options,
null );
    }
  }

}