Question

I have a handler class which implements ActionListner, FocusListner, and ItemListner. I have instantiated a gui object from a ConfrenceGUI class:

      public ConferenceGUI()
   {
      //Create a new JPanel and set its latyout mgr   
      conference = new JPanel(); 
      setLayout(new BorderLayout());  
      //create a RegPanel panel           
      regPanel = new RegPanel();
      //create new WorkshopPanel workshopPanel
      workshopPanel = new WorkshopPanel();      
      //build a buttonpanel
      buildButtonPanel();
      //Create a title panel      
      titlePanel = new JPanel(new FlowLayout());
      //create and set a font object
      titlePanel.setFont(new Font ("sansserif", Font.BOLD, 18));
      //add a label
      titlePanel.add(new Label("Select Registration Options"));      
      //Add the instantiated subpanels to the main conference gui panel
      add(titlePanel,        BorderLayout.NORTH);
      add(regPanel,          BorderLayout.WEST);
      add(workshopPanel,     BorderLayout.EAST);
      add(buttonPanel,       BorderLayout.SOUTH);
      //add an item listener to the combo box
      ConferenceHandler handler = new ConferenceHandler(this);
      regPanel.regComboBox.addItemListener(handler);
      //add a focus listener to the name field
      ConferenceHandler fhandler = new ConferenceHandler(this);
      regPanel.regTextField.addFocusListener(fhandler);
   }

I am trying to take information from the listeners (including two button listeners from a separate method in my ConferenceGUI class, which I did not include).

Here is a snipped of code from my handler:

  public void itemStateChanged(ItemEvent e)
  {
     String name = gui.regPanel.regTextField.getText(); 
     if (e.getSource() == gui.regPanel.regComboBox)
       {
          if (gui.regPanel.getRegType() == "Please select a type")
          JOptionPane.showMessageDialog(null, "Please select a registraion type",
                                        "Type Error", JOptionPane.ERROR_MESSAGE);     
          else gui.textArea.setText(name+" is a " +
                                        gui.regPanel.getRegType()+ " registration");
       }

and for the buttons:

      public void actionPerformed (ActionEvent e)
  {
    String name = gui.regPanel.regTextField.getText();
    DecimalFormat $ = new DecimalFormat("$#,##0.00");
    if (e.getSource() == gui.calcButton)//if the calculate buttton is pressed
    {
       //dislplay error box if user selects index 0
       if (gui.regPanel.getRegType() == "Please select a type")
         JOptionPane.showMessageDialog(null, "Please select a registraion type",
                                                "Type Error",JOptionPane.ERROR_MESSAGE);
       //prints to textarea if registrant will be attending keynote or not
       if (gui.regPanel.regCheckBox.isSelected())
          gui.textArea.setText("Keynote address will be attended");
            else
              gui.textArea.setText("Keynote address will not be attended");
       //prints to textarea which workshops registrant will be attending
       gui.textArea.setText(name+" is registered in these workshops:" +
                            gui.workshopPanel.getWorkshopList());
       //prints total registration fees to textarea
       gui.textArea.setText("Total charges for" + name + " are " + $.format(calcTotalCharges()));
    }
    else if (e.getSource() == gui.clearButton)//if the clear button is pressed
    {
       //clear the textarea 
       gui.textArea.setText("");  
       //reset the list
       gui.workshopPanel.workshopList.setSelectedIndex(0);
       //reset the combobox to index 0
       gui.regPanel.regComboBox.setSelectedIndex(0);
    }
  }

Problem will be obvious to all of you, but as I am just starting out, I can’t figure out why I can’t write any text into the textArea of my GUI. Apologies for the amount of code, but I wanted to try to be thorough.

Here is where the textarea comes from (which is a sperarate method contained in my ConferenceGUI class:

   private void buildButtonPanel()
   {
      //create the buttonpanel
      buttonPanel = new JPanel(new FlowLayout());
      //create the buttons
      calcButton = new JButton("Calculate Charges");
      clearButton = new JButton    ("Clear");
      //add listeners to the buttons
      ConferenceHandler ahandler = new ConferenceHandler(this);
      calcButton.addActionListener(ahandler);  
      clearButton.addActionListener(ahandler);
      //create a text area
      JTextArea textArea = new JTextArea(5,30); 
      textArea.setLineWrap(true); textArea.setWrapStyleWord(true);
      //add everything to the buttonpanel
      buttonPanel.add(calcButton); buttonPanel.add(clearButton); buttonPanel.add(new JScrollPane(textArea));
   }

There are three other classes RegPanel, and WorkshopPanel, both of which create a couple of panels for the ConferenceGUI, which is in turn instantiated by an applet (gui).

Answer 1

I’m not sure I understand your question (what doesn’t work? What do you expect and what happens?), but what’s sure is that calling setText() multiple times on a JTextArea is not a good idea : setText replaces the whole content of the text area. You should use append() to add multiple lines of text to the text area.

EDITED :

Now that you showed us how you built the text area, the problem is clearer : you instantiate a local variable textArea in the buildButtonPanel method, but the instance variable in your GUI points to another text area (or null).

EDITED again :

Your code is too complex and not complete enough to correct it, but the situation looks like this one :

public class Bug extends JPanel {
    private JTextArea textArea = new JTextArea(); // first text area

    private void build()  {
        JTextArea textArea = new JTextArea(); // second text area. Inaccessible outside of this method
        this.add(new JScrollPane(textArea));
    }

    public void actionPerformed(ActionEvent e) {
        this.textArea.setText("foo"); // here, we modify the first text area, but it hasn't been added to the GUI, so it's invisible
    }
}

To fix it, you have to change it to this :

public class NoBug extends JPanel {
    private JTextArea textArea = new JTextArea(); // unique text area

    private void build()  {
        this.add(new JScrollPane(this.textArea));
    }

    public void actionPerformed(ActionEvent e) {
        this.textArea.setText("foo"); // here, we modify the unique text area, which has been added to the GUI in the build() method        }
}