Executing an actionlistener in separate class

Question

Hi all,
This is my first question on the Java forum. Hope I express myself clearly and I hope that someone can help me.
I have created two classes (i.e. modified files that I found in Java books) - one which creates the user interface using JFrame (a text field and menu structure) and a second class which is basically the action listener for when the "menuFileLoad" button is pressed in the application.
I would like to move the code for all "actionlisteners" to separate classes to make the code more transparent.
I've moved the code for the action listener for the "menuFileLoad" button to the separate class "alistener".
The code compiles well, but the action in the alistener class is not performed. It should put "Another text" in a text field. For test purposes, I've also put
"System.out.println ("dada");" in the action listener and this is executed well.
Has it something to do with the accessibility of the "TextField" ?
This is the class that builds up the GUI
import java.awt.*;
import java.awt.event.*;
import java.lang.Object;
import java.awt.Container;
import javax.swing.JFileChooser;
* Sample application using Frame.
* @author
* @version 1.00 08/09/10
public class Getstring_ArrayFrame extends Frame {
     * The constructor.
     public TextField text = new TextField(20);
     public Getstring_ArrayFrame() {
        MenuBar menuBar = new MenuBar();
        Menu menuFile = new Menu();
        MenuItem menuFileExit = new MenuItem();
        MenuItem menuFileLoad = new MenuItem();
        MenuItem menuFileParse = new MenuItem();
        Menu menuFileTwo = new Menu();
        MenuItem menuFileDo = new MenuItem();
        menuFile.setLabel("File");
        menuFileExit.setLabel("Exit");
        menuFileLoad.setLabel("Load");
        menuFileDo.setLabel("Import Tool");
        menuFileParse.setLabel("Parse");
        menuFileTwo.setLabel("Tools");
        add(text);
        // Add action listener.for the menu button
        menuFileExit.addActionListener
            new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    Getstring_ArrayFrame.this.windowClosed();
// DIT IS HEM - DE EERSTE ECHTE ACTION LISTENER
       menuFileLoad.addActionListener (new alistener ());
           // new ActionListener() {
             //   public void actionPerformed(ActionEvent e) {
               // text.setText ("Eerste tekstje, joepie. Misschien nu nog den xml erbij krijgen");
               // text.setBackground(Color.black);
               // text.setForeground(Color.white);
menuFileParse.addActionListener
            new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                text.setText ("Opnieuw een tekstje, met tevens ook al een nieuwe knop.");
                //text.setBackground(Color.black);
                // text.setForeground(Color.white);
        menuFile.add(menuFileExit);
        menuFile.add(menuFileLoad);
        menuFile.add(menuFileParse);
        menuFileTwo.add(menuFileDo);
        menuBar.add(menuFile);
        menuBar.add(menuFileTwo);
        setTitle("Getstring_Array");
        setMenuBar(menuBar);
        setSize(new Dimension(400, 400));
        // Add window listener.
        this.addWindowListener
            new WindowAdapter() {
                public void windowClosing(WindowEvent e) {
                    Getstring_ArrayFrame.this.windowClosed();
     * Shutdown procedure when run as an application.
    protected void windowClosed() {
         // TODO: Check if it is safe to close the application
        // Exit application.
        System.exit(0);
}==> This is the alistener class
import java.awt.*;
import java.awt.event.*;
import java.lang.Object;
import java.awt.Container;
import javax.swing.JFileChooser;
public class alistener implements ActionListener {
     TextField text = new TextField(20);
public alistener () {
public void actionPerformed(ActionEvent e) {
              System.out.println ("dada");
               text.setText ("Another text.");
               text.setBackground(Color.black);
               text.setForeground(Color.white);
}

Answer 1

I don't know AWT, just Swing, but it appears that your listener needs a reference to the GUI which may be passed perhaps in the Listener's constructor, and the GUI needs public methods to allow the listener to change things -- but to limit this ability so as not to compromise encapsulation. This should work the same with AWT For instance:
import java.awt.Color;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JComponent;
import javax.swing.JTextField;
public class SwingTest
  private JPanel mainPanel = new JPanel();
  private JTextField textfield = new JTextField(20);
  public SwingTest()
    textfield.setEditable(false);
    JButton testListenerBtn = new JButton("Test Listener");
    testListenerBtn.addActionListener(new SwingTestListener(this));
    mainPanel.add(textfield);
    mainPanel.add(testListenerBtn);
  // public methods to allow the listener to change things,
  // but limit this ability to only what we want to let it change
  public void textfieldSetText(String text)
    textfield.setText(text);
  public void textSetBackground(Color color)
    textfield.setBackground(color);
  public void textSetForeGround(Color color)
    textfield.setForeground(color);
  public JComponent getComponent()
    return mainPanel;
  private static void createAndShowUI()
    JFrame frame = new JFrame("SwingTest");
    frame.getContentPane().add(new SwingTest().getComponent());
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
  public static void main(String[] args)
    java.awt.EventQueue.invokeLater(new Runnable()
      public void run()
        createAndShowUI();
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class SwingTestListener implements ActionListener
  private SwingTest swingtest;
  public SwingTestListener(SwingTest swingtest)
    this.swingtest = swingtest;
  public void actionPerformed(ActionEvent arg0)
    swingtest.textfieldSetText("This Listener works!");
    swingtest.textSetBackground(Color.black);
    swingtest.textSetForeGround(Color.white);
}Edited by: Encephalopathic on Nov 5, 2008 12:27 AM