itemStateChanged and actionPerformed issues

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 开发者_如何转开发a couple of panels for the ConferenceGUI, which is in turn instantiated by an applet (gui).

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        }
}

Apologies for the amount of code, but I wanted to try to be thorough

Actually the code you posted doesn't help much because we don't know the context of how the code is used.

Your code references a "gui" object, but we don't know when/how this variable is created. You reference a "textArea" object as well and same comment. So the code you posted is incomplete.

If you can't add text to a text area then one of two things is happening:

a) the code is not ever being executed (you can add System.out.println(...) to verify this). b) you have the wrong reference to the textArea compnent that has been added to the GUI. There could be many reasons for this. Maybe you have both a class and local variable of the same name.

If you need more help post your SSCCE that demonstrates the problem.