Overviewof Swing

 

🎨 Swing in Java 

Swing is a GUI toolkit in Java used to create rich desktop applications. It is part of the Java Foundation Classes (JFC) and provides a more powerful and flexible alternative to AWT.

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🧾 What is Swing?

• Swing is in the javax.swing package.

• It builds on top of AWT but does not rely on native GUI components, making it platform-independent in look and behavior.

• All Swing components are lightweight (they do not depend on OS-specific GUI).

• Supports pluggable look and feel, MVC architecture, and advanced components like trees, tables, tabbed panes, etc.

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🧱 Architecture of Swing

Swing follows a Model-View-Controller (MVC) architecture:

• Model: Holds data

• View: Renders the component

• Controller: Handles user interaction

Though this is more simplified in modern Swing development, the separation helps customize behavior and appearance independently.

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🎯 Features of Swing

Feature	Description
Lightweight	Doesn’t rely on native system components
Pluggable Look and Feel	Can change appearance dynamically
Rich Set of Widgets	Includes advanced components (tables, trees, sliders)
Custom Rendering	Can override painting behavior easily
Multithreaded	Uses Event Dispatch Thread (EDT) for UI updates

🧰 Commonly Used Swing Components

Component	Description
JFrame	Main window
JPanel	Generic container
JButton	Push button
JLabel	Text label
JTextField	Single-line input
JTextArea	Multi-line text input
JCheckBox	Checkbox
JRadioButton	Radio button
JComboBox	Drop-down
JList	List box
JTable	Display tabular data
JTabbedPane	Tabbed panels
JScrollPane	Scrollbars
JMenuBar, JMenu, JMenuItem	Menu system

🧪 Simple Example: Swing Program

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

public class MySwingApp {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Swing Example");

        JLabel label = new JLabel("Enter your name:");
        label.setBounds(50, 50, 120, 30);

        JTextField tf = new JTextField();
        tf.setBounds(180, 50, 150, 30);

        JButton button = new JButton("Click Me");
        button.setBounds(150, 100, 100, 30);

        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String name = tf.getText();
                JOptionPane.showMessageDialog(frame, "Hello, " + name + "!");
            }
        });

        frame.add(label);
        frame.add(tf);
        frame.add(button);

        frame.setSize(400, 250);
        frame.setLayout(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

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📐 Layout Managers in Swing

Swing uses layout managers to organize components:

Layout Manager	Description
FlowLayout	Left to right flow
BorderLayout	Regions: North, South, East, West, Center
GridLayout	Table-like layout
BoxLayout	Components stacked either vertically or horizontally
GridBagLayout	Advanced grid (most flexible)

Example:

frame.setLayout(new FlowLayout());

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🧠 Event Handling in Swing

Uses the Event Delegation Model like AWT.

Common interfaces:

• ActionListener – Button clicks

• ItemListener – Checkboxes, radio buttons

• KeyListener – Keyboard input

• MouseListener – Mouse events

Example:

button.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        // action on click
    }
});

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📦 Important Swing Containers

Container	Description
JFrame	Top-level window
JDialog	Pop-up dialog
JPanel	Generic container
JApplet	Used in applets (older technology)

🌈 Pluggable Look and Feel

Swing supports changing the GUI appearance dynamically:

UIManager.setLookAndFeel("javax.swing.plaf.nimbus.NimbusLookAndFeel");
SwingUtilities.updateComponentTreeUI(frame);

Other options:

• Metal (default)

• Nimbus

• Motif

• Windows (on Windows OS)

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🧵 Threading in Swing

All GUI code should run on the Event Dispatch Thread (EDT):

SwingUtilities.invokeLater(() -> {
    new MySwingApp();
});