Swing in java with example

Java Swing is a part of Java Foundation Classes (JFC) that provides a rich set of GUI components for Java applications. It is built on top of AWT (Abstract Window Toolkit) but is lightweight, meaning it doesn’t depend on the native system. Instead, Swing components are rendered entirely in Java.

Key Features of Swing

Platform Independence: Swing applications are portable across different operating systems.
Rich Set of Components: Includes buttons, text fields, tables, trees, and more.
Pluggable Look-and-Feel: You can change the appearance of the Swing components dynamically.
Lightweight Components: Swing components are lightweight and more flexible compared to AWT.
Event-Driven Programming: Swing supports event handling to respond to user actions.

Swing Architecture

Swing is based on the Model-View-Controller (MVC) architecture. Each component in Swing separates the data (Model), presentation (View), and control logic (Controller). This separation allows for more modular and maintainable code.

Model: Represents the data and business logic of the application.
View: Displays the model data to the user.
Controller: Responds to user input and modifies the model.

Basic Swing Components

Here are some of the most commonly used Swing components:

JFrame: The main window for the application.
JPanel: A generic container that can hold other components.
JButton: A push button that can trigger actions.
JLabel: Displays a short string or an image icon.
JTextField: A single-line text input field.
JTextArea: A multi-line text input area.
JComboBox: A drop-down list of items.
JList: Displays a list of items for selection.
JTable: Displays data in a tabular format.
JTree: Displays data in a hierarchical format.

Getting Started with Swing

To create a simple Swing application, you can follow these steps:

Set Up Your Environment: Ensure you have Java installed and an IDE (like Eclipse, IntelliJ IDEA, or NetBeans).
Create a JFrame: This will be the main window of your application.
Add Components: You can add various Swing components to the JFrame.
Handle Events: Use action listeners to respond to user inputs.

Example: A Simple Swing Application

Let’s build a simple Swing application that calculates the sum of two numbers. This application will demonstrate how to create a JFrame, add components, and handle events.

Step 1: Create the Main Class

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

public class SimpleCalculator extends JFrame {

    private JTextField num1Field;
    private JTextField num2Field;
    private JButton addButton;
    private JLabel resultLabel;

    public SimpleCalculator() {
        setTitle("Simple Calculator");
        setSize(300, 200);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new FlowLayout());

        num1Field = new JTextField(10);
        num2Field = new JTextField(10);
        addButton = new JButton("Add");
        resultLabel = new JLabel("Result: ");

        add(num1Field);
        add(num2Field);
        add(addButton);
        add(resultLabel);

        addButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                addNumbers();
            }
        });
    }

    private void addNumbers() {
        try {
            double num1 = Double.parseDouble(num1Field.getText());
            double num2 = Double.parseDouble(num2Field.getText());
            double sum = num1 + num2;
            resultLabel.setText("Result: " + sum);
        } catch (NumberFormatException e) {
            resultLabel.setText("Please enter valid numbers.");
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            SimpleCalculator calculator = new SimpleCalculator();
            calculator.setVisible(true);
        });
    }
}

Explanation of the Code

Class Declaration: We create a class SimpleCalculator that extends JFrame.
Components: We define a text field for each number, a button for the addition, and a label to display the result.
Constructor:
- Set the title and size of the JFrame.
- Define a layout using FlowLayout.
- Add components to the JFrame.
- Attach an action listener to the button to handle click events.
addNumbers Method: This method retrieves the numbers from the text fields, performs the addition, and updates the result label. It also handles any input errors.
Main Method: The main method creates an instance of the SimpleCalculator and sets it visible on the Event Dispatch Thread (EDT).

Layout Managers

Swing provides several layout managers to control the positioning and sizing of components. Here are some common layout managers:

FlowLayout: Places components in a row, wrapping to the next line as necessary.
BorderLayout: Divides the container into five regions: north, south, east, west, and center.
GridLayout: Arranges components in a grid of specified rows and columns.
BoxLayout: Aligns components either vertically or horizontally.

Example of Using GridLayout

Let’s modify our previous example to use a GridLayout for better organization.

public class GridCalculator extends JFrame {

    public GridCalculator() {
        setTitle("Grid Calculator");
        setSize(300, 150);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new GridLayout(3, 2));

        JTextField num1Field = new JTextField(10);
        JTextField num2Field = new JTextField(10);
        JButton addButton = new JButton("Add");
        JLabel resultLabel = new JLabel("Result: ");

        add(num1Field);
        add(num2Field);
        add(addButton);
        add(resultLabel);

        addButton.addActionListener(e -> {
            double num1 = Double.parseDouble(num1Field.getText());
            double num2 = Double.parseDouble(num2Field.getText());
            double sum = num1 + num2;
            resultLabel.setText("Result: " + sum);
        });
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            GridCalculator calculator = new GridCalculator();
            calculator.setVisible(true);
        });
    }
}

Advanced Swing Features

Custom Look-and-Feel: You can change the appearance of your Swing application by using different look-and-feel options provided by the UIManager class.

try {
    UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
} catch (Exception e) {
    e.printStackTrace();
}

2.Menus and Toolbars: You can create menus and toolbars using JMenuBar, JMenu, and JToolBar components

JMenuBar menuBar = new JMenuBar();
JMenu fileMenu = new JMenu("File");
JMenuItem exitItem = new JMenuItem("Exit");
exitItem.addActionListener(e -> System.exit(0));
fileMenu.add(exitItem);
menuBar.add(fileMenu);
setJMenuBar(menuBar);

3.Dialogs: Swing provides pre-built dialog boxes for various tasks, such as showing messages, asking for confirmation, or getting user input.

JOptionPane.showMessageDialog(this, "Hello, World!");

Event Handling

Swing uses the delegation event model, which means that components (the source) notify listeners (the handlers) about events. You can implement event listeners by defining classes that implement the required interfaces or using lambda expressions (as seen in our examples).

Common event interfaces include:

ActionListener: For button clicks and menu item selections.
MouseListener: For mouse actions (clicks, presses, releases).
KeyListener: For keyboard actions.

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Swing in java with example

Key Features of Swing

Swing Architecture

Basic Swing Components

Getting Started with Swing

Example: A Simple Swing Application

Step 1: Create the Main Class

Explanation of the Code

Layout Managers

Example of Using GridLayout

Advanced Swing Features

Event Handling

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