Swing Event Handling

Event Handling in Swing is based on the delegation event model, where an event source (component) notifies one or more listeners when an event occurs.

Key Concepts

  • Event Source: The component that generates an event (e.g., JButton)
  • Event Listener: An interface that receives and processes the event (e.g., ActionListener)
  • Event Object: Carries information about the event (e.g., ActionEvent)

Example: Handling Button Click

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

public class EventExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Event Example");
        JButton button = new JButton("Click Me");

        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                System.out.println("Button clicked!");
            }
        });

        frame.add(button);
        frame.setSize(200, 150);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

Lambda Version (Java 8+)

button.addActionListener(e -> System.out.println("Clicked!"));

Event Flow

  1. User interacts with a component (e.g., clicks a button).
  2. Component generates an event object.
  3. Event object is passed to the registered listener’s method.

🔗 Related Notes