Delegation Event Model

Question

Hey ,
I am trying to understand the java event handling with swing . I have got good responses from urhand ( thanks for all your responses :) ) but I have a different approach to it. I am primarily a actionscript developer so I`ll try and explain to the best of my abilities what I am trying to achieve with swing here.
Let us take a very simple example a LoginManager class which basically has 2 JLabes and 2 Textfields and one button.
So I would like to make my LoginManager class to dispatch an event which would send the username and password and my MainApp class have the call back function to it.
Here is what the actionscript code would look like
import mx.events.EventDispatcher;
class Login extends MovieClip{
private var okButton:Button
private var userName:TextField;
private var dispatchEvent:Function;
public var addEventListener:Function;
public function Login (){
init();
private function init(){
EventDispatcher.initialize(this);
_okButton.onPress=sendEvent();
private function sendEvent(){
dispatchEvent({type:"onClick",target:this,username:userName.text});
class MyApp{
public function createGUI(){
var log:Login=new Login();
log.addEventListener("onClick",onLoginClick);
private function onLoginClick(eventObj:Object){
print(eventObj.username);
So basically the MainApp listens for a onClick event from Login and records the username. I am trying to achieve the same with java swing making . I was searching through the forums and I came accross this solution but I dont know how to or where to dispatch the events and how to set up the call back functions for my mainApp class
This is the way I want to create my App so I can dispatch events from one class to another sending whatever data I want to.
public interface InventorySelectionListener {
  public void inventoryChanged(InventorySelectionEvent ev);
public class InventoryPanel extends JPanel {
  public void addInventorySelectionListener(InventorySelectionListener listener) {
  public void removeInventorySelectionListener(InventorySelectionListener listener) {
public class Shop extends JFrame implements InventorySelectionListener {
    inventoryPanel.addInventoryListener(this);
  public void inventoryChanged(InventorySelectionEvent ev) {
}I hope I am making sense as to what I am trying to achieve / learn here.
Thanks :)
cheesrs :)
firdosh
[urhand .. thanks for your previous solutions  :) ]

Answer 1

You will need to learn MVC sooner or later... so why not sooner? This is a simple example, a real app would use JPasswordField.
So how does it work? Rather than listening for a change in the logon dialog, the logon dialog creates a container and puts some data in it. Then, the main class examines the contents, and finds the username & password.
This way, if the logon dialog completely changes but still uses the same container, then the main frame never needs to change. It's called a model-view separation.
public class LogonModel {
  public String userName;
  public String password;
  public boolean chooseOk = false;
public class MainApp exnteds JFrame {
  // Creates the main app.. etc.
  // Now it wants to show a login prompt.. so it calls this method:
  public void showLoginPrompt() {
    LogonModel model = new LogonModel();
    LogonDialog dialog = new LogonDialog(model);
    // makes all the labels and text field goto the right position
    dialog.pack()
    // puts it in the middle of the screen
    dialog.setLocationRelativeTo(null);
    // shows it... the flow stops here and does
    // not return until they close the dialog.
    dialog.show();
    if(model.chooseOk) {
        System.out.println("The user typed the name: " + model.userName);
        System.out.println("The user typed the pass: " + model.password);
     } else {
        System.out.println("The user canceled logon!");
public class LogonDialog extneds JDialog {
  LogonModel logonModel;
  public LogonDialog(LogonModel model) {
    this.logonModel = model;
  // somewhere in your dialog you will create the buttons...
  // create your OK button like this:
  JButton okButton = new JButton("OK");
  okButton.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
      // fills the model with data
      model.chooseOk = true;
      model.userName = userNameTextField.getText();
      model.password = passwordTestField.getText();
      close(); // closes the logon dialog.
}