Java Swing

🖼️ What is Java Swing?

Java Swing is a mature GUI toolkit for building desktop applications. It provides a rich set of lightweight components that work across different platforms with consistent look and feel.


// Simple Swing Application
import javax.swing.*;

public class HelloSwing {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Hello Swing");
        JLabel label = new JLabel("Welcome to Swing!");
        
        frame.add(label);
        frame.setSize(300, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

Output:

Welcome to Swing!

Key Swing Concepts

🖼️

JFrame

Main window container

JFrame frame = new JFrame("Title");
frame.setSize(400, 300);

🎛️

Components

UI elements like buttons, labels

JButton btn = new JButton("Click");
JLabel lbl = new JLabel("Text");

📐

Layout Managers

Control component positioning

frame.setLayout(new FlowLayout());
frame.setLayout(new BorderLayout());

👆

Event Handling

Respond to user actions

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

🔹 Basic Swing Components

Essential components for building Swing applications:

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

public class SwingComponents {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Swing Components");
        
        // Text components
        JLabel label = new JLabel("Enter your name:");
        JTextField textField = new JTextField(20);
        JTextArea textArea = new JTextArea(5, 20);
        
        // Buttons
        JButton button = new JButton("Submit");
        JCheckBox checkBox = new JCheckBox("Remember me");
        JRadioButton radio1 = new JRadioButton("Option 1");
        JRadioButton radio2 = new JRadioButton("Option 2");
        
        // Group radio buttons
        ButtonGroup group = new ButtonGroup();
        group.add(radio1);
        group.add(radio2);
        
        // Lists and combos
        String[] items = {"Item 1", "Item 2", "Item 3"};
        JComboBox<String> combo = new JComboBox<>(items);
        JList<String> list = new JList<>(items);
        
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 300);
        frame.setVisible(true);
    }
}

🔹 Layout Managers

Different ways to arrange components in containers:

// FlowLayout - components in a row
JPanel flowPanel = new JPanel(new FlowLayout());
flowPanel.add(new JButton("Button 1"));
flowPanel.add(new JButton("Button 2"));

// BorderLayout - five regions
JPanel borderPanel = new JPanel(new BorderLayout());
borderPanel.add(new JButton("North"), BorderLayout.NORTH);
borderPanel.add(new JButton("Center"), BorderLayout.CENTER);
borderPanel.add(new JButton("South"), BorderLayout.SOUTH);

// GridLayout - rows and columns
JPanel gridPanel = new JPanel(new GridLayout(2, 3));
for (int i = 1; i <= 6; i++) {
    gridPanel.add(new JButton("Button " + i));
}

// BoxLayout - vertical or horizontal
JPanel boxPanel = new JPanel();
boxPanel.setLayout(new BoxLayout(boxPanel, BoxLayout.Y_AXIS));
boxPanel.add(new JButton("Top"));
boxPanel.add(new JButton("Middle"));
boxPanel.add(new JButton("Bottom"));

🔹 Event Handling

Responding to user interactions in Swing:

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

public class EventExample extends JFrame {
    private JTextField textField;
    private JLabel resultLabel;
    
    public EventExample() {
        setTitle("Event Handling Example");
        setLayout(new FlowLayout());
        
        textField = new JTextField(15);
        JButton button = new JButton("Click Me");
        resultLabel = new JLabel("Result will appear here");
        
        // Action listener for button
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String text = textField.getText();
                resultLabel.setText("You entered: " + text);
            }
        });
        
        // Lambda expression (shorter way)
        button.addActionListener(e -> {
            String text = textField.getText();
            resultLabel.setText("You entered: " + text);
        });
        
        add(new JLabel("Enter text:"));
        add(textField);
        add(button);
        add(resultLabel);
        
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(400, 150);
        setVisible(true);
    }
    
    public static void main(String[] args) {
        new EventExample();
    }
}