JComboBox ActionListener

[moxy]

Hello again all,

I'm still trying to work out my JComboBox and I'm having trouble with my ActionListener. I would like to have some JLabels change when I make a selection in my box.

public void admitPane(){
		
   JLabel labelAdmit = new JLabel ("Admit");
   JPanel admitCard = new JPanel();
			
   JLabel label1=new JLabel();
   JLabel label2=new JLabel();
   JLabel label3=new JLabel();
			
   admitCard.add (labelAdmit);
   deck.add (admitCard, "Admit");
   JComboBox studentBox = new JComboBox(nameArray);
		  

   admitCard.add (studentBox);
			
   studentBox.addActionListener(this); 

   JRadioButton a1 = new JRadioButton ("accept", false);
   JRadioButton r1 = new JRadioButton ("reject", true);
   JRadioButton a2 = new JRadioButton ("accept", false);
   JRadioButton r2 = new JRadioButton ("reject", true);
   JRadioButton a3 = new JRadioButton ("accept", false);
   JRadioButton r3 = new JRadioButton ("reject", true);

   ...

if (event.getSource() == studentBox)
{
   studentIndex  =studentBox.getSelectedIndex(); 
   school1 =arrayOfStudents[studentIndex].getUniversity(0);
   school2 =arrayOfStudents[studentIndex].getUniversity(1);
   school3 =arrayOfStudents[studentIndex].getUniversity(2);
   label1.setText (school1);
   label2.setText(school2);
   label3.setText (school3);
						 
   school1 =arrayOfStudents[studentIndex].getUniversity(0);
   school2 =arrayOfStudents[studentIndex].getUniversity(1);
   school3 =arrayOfStudents[studentIndex].getUniversity(2);
   label1.setText (school1);
   label2.setText(school2);
   label3.setText (school3);

[sjalle]

You are adding the panel to the combobox's actionlisteners, then you
respond to selections (actions) in that combo by setting the texts in some JLabels.

If that doesn't work you must have missed out on something.

I'm am unable to see the error here ?

I have tested it also, so I am 100 % sure:

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

/**
 *
 */

public class SetLabelText extends JFrame implements ActionListener {
  JPanel centerPanel = new JPanel();
  JLabel lbl1 = new JLabel();
  JLabel lbl2 = new JLabel();
  JLabel lbl3 = new JLabel();
  JComboBox combo = new JComboBox();


  private void fillCombo() {
    combo.addItem("Test1");
    combo.addItem("Test2");
    combo.addItem("Test3");
    combo.addActionListener(this);
  }
  public SetLabelText(String title) {
    super(title);
    jbInit();
    fillCombo();
  }
  public void actionPerformed(ActionEvent e) {
    if (e.getSource()==combo) {
      String s=(String)combo.getSelectedItem();
      lbl2.setText(s);
    }
  }

  public static void main(String[] args) {
    SetLabelText slt = new SetLabelText("Labels");
    slt.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    slt.setBounds(20,20,400,200);
    slt.setVisible(true);
  }
  private void jbInit() {
    lbl1.setBorder(BorderFactory.createLineBorder(Color.black));
    lbl1.setText("lbl1");
    lbl2.setBorder(BorderFactory.createLineBorder(Color.black));
    lbl2.setText("lbl2");
    lbl3.setBorder(BorderFactory.createLineBorder(Color.black));
    lbl3.setText("lbl3");
    combo.setPreferredSize(new Dimension(120, 25));
    this.getContentPane().add(centerPanel, BorderLayout.CENTER);
    centerPanel.add(lbl1, null);
    centerPanel.add(lbl2, null);
    centerPanel.add(lbl3, null);
    centerPanel.add(combo, null);
  }

}

[moxy]

OK, then it must be in my implimentation (again)...

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

public class ApplicationCentre extends JApplet implements ActionListener
{
   Student[] arrayOfStudents;
   Object[] jListArray;
   String[] nameArray = new String[100];
   private JPanel main, deck;
   private JLabel labelName, labelAvg, counter, label1, label2, label3;
   private JButton input, admit, display, submit, admitSubmit;
   private Container container;
   private CardLayout cardManager;
   private JTextField name, avg;
   private JList schools;
   private int studentIndex;
   private int count=0;
   private int i = 0;
   private int mark = 0;
   private JComboBox studentBox;
   private String nameOfStudent;
   private JRadioButton a1, a2, a3, r1, r2, r3;
   private String school1, school2, school3;
   private JTextArea displayText;
   private String textHolder=("");
   // End of variables declaration
 
   public void init ()
   {
      initComponents();
      setSize(400, 210);
   }  
	 
   public void initComponents() 
   {
       container = getContentPane();
       container.setLayout( new BorderLayout() );        
      
       // Creating instances of each item  
       main = new JPanel();
       input = new JButton("Input");
       admit = new JButton("Admit");
       display = new JButton("Display");
       arrayOfStudents = new Student[100];
		  
       school1 = ("");
       school2 = ("");
       school3 = ("");
	  
       // End Creation 
		
      //set up main menu		
       main.setLayout (new GridLayout (3,1));
       main.add(input);
       main.add (admit);
       main.add (display);
	  
       //set up deck
       cardManager = new CardLayout();
       deck = new JPanel(cardManager);
		 		  		  
       //Input Card
       inputPane();
		  
       //Display Card
       JLabel labelDisplay = new JLabel ("Display");
       JPanel displayCard = new JPanel();
       displayCard.setLayout (new BoxLayout (displayCard, BoxLayout.PAGE_AXIS));
       JTextArea displayText = new JTextArea ("This is a JTextArea");
		  
		  
       displayText.setFont(new Font("Serif", Font.ITALIC, 12)); 
       //textArea.setLineWrap(true); 
       //textArea.setWrapStyleWord(true); 
       displayText.setEditable(false);

       displayCard.add (labelDisplay);
       deck.add (displayCard, "Display");	
		  
       JScrollPane areaScrollPane = new JScrollPane(displayText); 
       areaScrollPane.setVerticalScrollBarPolicy( JScrollPane.VERTICAL_SCROLLBAR_ALWAYS); 
       displayCard.add(areaScrollPane);	
       //displayCard.add(displayText);
		  
       //add listeners
       input.addActionListener (this);
       admit.addActionListener (this);
       display.addActionListener (this);
		  
       //listener for input
       submit.addActionListener (this);

       //add components to screen	
        container.add( main, BorderLayout.WEST);
        container.add(deck, BorderLayout.CENTER);
		  
		  
    }//end applicationCentre	  
	
       //INPUT PANE
       public void inputPane(){
       labelName = new JLabel ("Name");
       name = new JTextField (10);
       labelAvg = new JLabel ("Average");
       avg = new JTextField (3);
       submit = new JButton ("Submit");
       counter = new JLabel ();
		 
       //school array
       String schoolArray[] = {"Toronto", "York", "Western", "Brock", "Guelph", "Waterloo", "McGill", "Concordia", "Laval", "MacMaster"};
       schools = new JList (schoolArray);
       schools.setVisibleRowCount(5);
       schools.setSelectionMode (ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
			
       JPanel inputCard = new JPanel();
       inputCard.setLayout (new BoxLayout (inputCard, BoxLayout.PAGE_AXIS));
        inputCard.add (labelName);
        inputCard.add (name);
        inputCard.add (labelAvg);
        inputCard.add (avg);
        inputCard.add (new JScrollPane (schools));
        inputCard.add (submit);
        inputCard.add (counter);
		  
        deck.add (inputCard, "Input");
	
        }//end input pane
		
       //admit pane
        public void admitPane(){
		
       JLabel labelAdmit = new JLabel ("Admit");
       JPanel admitCard = new JPanel();
       admitCard.setLayout (new BoxLayout (admitCard, BoxLayout.PAGE_AXIS));
       JButton admitSubmit = new JButton ("Submit");
			
       JLabel label1=new JLabel();
       JLabel label2=new JLabel();
       JLabel label3=new JLabel();
			
       admitCard.add (labelAdmit);
       deck.add (admitCard, "Admit");
       JComboBox studentBox = new JComboBox(nameArray);
		  
       admitCard.add (studentBox);
			
       studentBox.addActionListener(this);
       admitSubmit.addActionListener(this); 
       JRadioButton a1 = new JRadioButton ("accept", false);
       JRadioButton r1 = new JRadioButton ("reject", true);
       JRadioButton a2 = new JRadioButton ("accept", false);
       JRadioButton r2 = new JRadioButton ("reject", true);
       JRadioButton a3 = new JRadioButton ("accept", false);
       JRadioButton r3 = new JRadioButton ("reject", true);
			
       ButtonGroup radioGroup1 = new ButtonGroup();
       radioGroup1.add(a1);
       radioGroup1.add(r1);

       ButtonGroup radioGroup2 = new ButtonGroup();
       radioGroup2.add(a2);
       radioGroup2.add(r2);
			
       ButtonGroup radioGroup3 = new ButtonGroup();
       radioGroup3.add(a3);
       radioGroup3.add(r3);
			
       admitCard.add (label1);
       admitCard.add (a1);
       admitCard.add (r1);
       admitCard.add (label2);
       admitCard.add (a2);
       admitCard.add (r2);	
       admitCard.add (label3);
       admitCard.add (a3);
       admitCard.add (r3);

       admitCard.add (admitSubmit);

       }//end admit pane
			  
       //buttons!!
       public void actionPerformed (ActionEvent event)  {
	  
       //show cards
       if (event.getSource() == input)
          cardManager.show(deck, "Input");
       else if (event.getSource ()== admit)
          {
           admitPane();
           cardManager.show (deck, "Admit");
          } //end admit if

       else if (event.getSource()==display){
           for ( int r = 0; r < count; r++ ) 
	{ 
                 textHolder = (textHolder+arrayOfStudents[r]+"\n"); 
                }
		  
         //displayText.setText(textHolder); //Why is this line giving me so much grief???
        cardManager.show (deck, "Display");
       }

       //submit button
       if (event.getSource() == submit){
	String s1=name.getText();
	String s2=avg.getText();
	mark=Integer.parseInt(s2);
	Object [] o=schools.getSelectedValues();
				
	String choice1 = (String)o[0];
	String choice2 = (String)o[1];
	String choice3 = (String)o[2];
	arrayOfStudents[count]=new Student(s1, mark, choice1, choice2, choice3);
	nameArray[count]=new String(s1); 
	name.setText("");
	avg.setText("");
	schools.clearSelection();
	count ++;
	counter.setText ("Student " + count + " out of 100");
	}//end submit button
				
       //jComboBox
       if (event.getSource() == studentBox)
       {
           //u1.setText(school1);
           studentIndex  =studentBox.getSelectedIndex(); 
           school1 =arrayOfStudents[studentIndex].getUniversity(0);
           school2 =arrayOfStudents[studentIndex].getUniversity(1);
           school3 =arrayOfStudents[studentIndex].getUniversity(2);
           label1.setText (school1);
           label2.setText(school2);
           label3.setText (school3);
	
           //studentIndex  =studentBox.getSelectedIndex(); 
           school1 =arrayOfStudents[studentIndex].getUniversity(0);
           school2 =arrayOfStudents[studentIndex].getUniversity(1);
           school3 =arrayOfStudents[studentIndex].getUniversity(2);
           label1.setText (school1);
           label2.setText(school2);
           label3.setText (school3);
           }//end jcombobox
				
     if (event.getSource()==admitSubmit)
      {
         //Student.setAcceptance();
      }//end admitSubmit
   }//end button handler

}

[sjalle]

I cannot find anywhere in the code where the combobox is being added to any
container, - so it's invisible.

Once you have done that you must add one or more of the other objects to the
combobox's list of actionlisteners.

[moxy]

The comboBox is added above the buttonGroups.

JComboBox studentBox = new JComboBox(nameArray);
admitCard.add (studentBox);

It shows when compiled. The only problem is that when a selection is made in the combobox, it does not change the JLabels as it should.