dynamically adding components

[Alan Shiers]

Hi there,

I'm trying a test by adding components dynamically to a GUI. In the following test I am able to add a JLabel or a JButton, but when it comes to a JTextArea nothing appears. Can someone explain what I need to do to make the JTextArea appear?

Please advise,

Alan

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JFrame;
import javax.swing.BoxLayout;
import javax.swing.JPanel;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JTextArea;
 
public class PracticeGUI extends JFrame implements ActionListener
{

  JPanel testPanel = new JPanel();        

  public PracticeGUI()
  {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(300,400);
setTitle("Practice GUI");
getContentPane().setLayout(new BoxLayout(getContentPane(),BoxLayout.Y_AXIS));
JButton HitMe = new JButton("Hit Me!");
HitMe.addActionListener(new TestListener());
getContentPane().add(HitMe);
getContentPane().add(testPanel);
setVisible(true);
  }

  public void actionPerformed(ActionEvent e)
  {
  }

  class TestListener implements ActionListener
  {
public void actionPerformed(ActionEvent e)
        {
          //testPanel.add(new JButton("Blah"));  //<< This works
          //testPanel.add(new JLabel("Yeah!"));  //<< This works
 
          JTextArea jta = new JTextArea();  //<< This doesn't works.  How come?
  testPanel.add(jta);
 
  testPanel.validate();
                        
}
  }
 
  public static void main(String[] args)
  {
    PracticeGUI pgui = new PracticeGUI();           
  }
}    

[Tony Docherty]

It does work it's just that at a size of 0 x 0 there's not much to see . If you give it a size via the constructor or add some text to it, it will display something that is visible.