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Events on Java

  Asked By: Meenachi    Date: Aug 20    Category: Java    Views: 1147

Can someone tell me how to use events in Java? There's some class
or it's just a reserved word as in c#? If it's a class, which is it
and it locates in which package.



2 Answers Found

Answer #1    Answered By: Chau Tran     Answered On: Aug 20

You have to import java.awt.event*
then if you have a text field for example myTextField
you have to write a kinda special code, like:

myTextField.addActionListener (
new ActionListener()
public void actionPerformed (ActionEvent e)

// Whatever is gonna happen here

This is the way it works, the same goes for the other
listeners, but please check the API, I might have
misspelled something.

Answer #2    Answered By: Viheke Fischer     Answered On: Aug 20

Common events  are residing in java.awt.event package  and javax.swing.event
Basically all events are Interface types so there is only method
declaration, & allows you to inherit as many as Interface if u want.
While using these interfaces you have to override the method already
declared in parent interface and put some of your code here to do some action.
Basically java  SWING / AWT are using this Event Driven Model, simply user
has to Click / Enter something to do some action.

Some common properties for Events in Java

1. All Event Listeners are Interface & having public, void signatures,
so NO event will return something to user.
3. You can use Adapter classes if u dont want to override all the
methods of a Interface, in my example I have used WindowAdapter class  &
Overridden only windowClosing() method, simply Event Adapter will put null body
on the methods which u r not overridden
4. Interface methods have EventObject as parameter which will give
additional info about this Event, like getSource(), getX(),getY()
5. You can remove a listener to the component using
remove<ListenerName>() methods

if I am wrong on something here plz let me know


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

public class ActionDemo extends JFrame implements ActionListener
JButton jbtnDemo = new JButton("Click Here");

public ActionDemo()
super("Action Listener Demo");
Container c = getContentPane();
c.setLayout(new FlowLayout(FlowLayout.CENTER));

jbtnDemo.addActionListener(this); //this will add the listener to
this button so that if any body clicks this button the actionPerformed() method
will be fired

addWindowListener(new WindowAdapter()
public void windowClosing(WindowEvent we)

public void actionPerformed(ActionEvent ae)
if(ae.getSource() == jbtnDemo)
JOptionPane.showMessageDialog(this,"You have clicked on me
:)","Click Here",JOptionPane.INFORMATION_MESSAGE);

public static void main(String args[])
new ActionDemo();

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