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UNIT - 1 JAVA SWING

1. LAYOUT MANAGEMENT

Commonly Used Layout Managers in Java

Java provides several layout managers, each with unique rules for arranging components.

1. FlowLayout

Description: Arranges components in a row, wrapping to the next row if the space runs out.
Default Layout for: JPanel
Alignment Options: Left, center (default), or right.

Code Example:


JPanel panel = new JPanel(new FlowLayout(FlowLayout.CENTER));
panel.add(new JButton("Button 1"));
panel.add(new JButton("Button 2"));
panel.add(new JButton("Button 3"));

Use Cases: Simple layouts with a small number of components.

2. BorderLayout

Description: Divides the container into five regions: North, South, East, West, and Center.
Default Layout for: JFrame

Code Example:

JFrame frame = new JFrame();
frame.setLayout(new BorderLayout());
frame.add(new JButton("North"), BorderLayout.NORTH);
frame.add(new JButton("South"), BorderLayout.SOUTH);
frame.add(new JButton("East"), BorderLayout.EAST);
frame.add(new JButton("West"), BorderLayout.WEST);
frame.add(new JButton("Center"), BorderLayout.CENTER);

Use Cases: Organizing components around a central area.

3. GridLayout

Description: Arranges components in a grid with equal-sized cells.
Constructor Parameters: Rows, Columns (or just Rows with 0 for dynamic columns).
Code Example:

JPanel panel = new JPanel(new GridLayout(2, 2)); // 2 rows, 2 columns
panel.add(new JButton("Button 1"));
panel.add(new JButton("Button 2"));
panel.add(new JButton("Button 3"));
panel.add(new JButton("Button 4"));

Use Cases: When you need a tabular layout.

4. GridBagLayout

Description: A flexible and powerful layout manager allowing components to span multiple rows or columns.
Key Feature: Uses a GridBagConstraints object to define each component's size, position, and alignment.

Code Example:

JFrame frame = new JFrame();
frame.setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();

gbc.gridx = 0; gbc.gridy = 0;
frame.add(new JButton("Button 1"), gbc);

gbc.gridx = 1; gbc.gridy = 0;
frame.add(new JButton("Button 2"), gbc);

gbc.gridx = 0; gbc.gridy = 1;
frame.add(new JButton("Button 3"), gbc);

Use Cases: Complex layouts with precise control over positioning.

5. CardLayout

Description: Stacks components like cards, showing one at a time.

Code Example:

JPanel panel = new JPanel(new CardLayout());
panel.add(new JLabel("Card 1"), "Card1");
panel.add(new JLabel("Card 2"), "Card2");

CardLayout cl = (CardLayout) panel.getLayout();
cl.show(panel, "Card2");

Use Cases: Implementing tabbed views or wizards.

6. BoxLayout

Description: Arranges components either vertically (BoxLayout.Y_AXIS) or horizontally (BoxLayout.X_AXIS).

Code Example:

JPanel panel = new JPanel();
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
panel.add(new JButton("Button 1"));
panel.add(new JButton("Button 2"));

Use Cases: Stacking components in a single axis.

Custom Layouts

If none of the built-in layout managers meet your needs, you can create a custom layout by implementing the LayoutManager or LayoutManager2 interfaces.

Key Methods in Layout Managers

All layout managers use specific methods to arrange components:

addLayoutComponent(String name, Component comp): Adds a component with constraints.
removeLayoutComponent(Component comp): Removes a component.
preferredLayoutSize(Container parent): Returns the preferred size for the container.
minimumLayoutSize(Container parent): Returns the minimum size for the container.
layoutContainer(Container parent): Arranges components within the container.

Choosing the Right Layout Manager

FlowLayout: Simple layouts with a linear flow.
BorderLayout: Good for dividing a UI into major areas.
GridLayout: Ideal for grids and tables.
GridBagLayout: When precise control is required.
CardLayout: For swapping views or pages.
BoxLayout: For vertical or horizontal stacking.

Best Practices for Java Layout Management

Combine Layout Managers: Nest panels with different layouts for complex designs.
Use Insets and Padding: Adjust spacing for better aesthetics.
Minimize GridBagLayout Use: Use it only for truly complex needs due to its verbosity.
Test Responsiveness: Resize the container to ensure components adapt properly.

Example: Combining Layouts

JPanel mainPanel = new JPanel(new BorderLayout());
JPanel topPanel = new JPanel(new FlowLayout());
JPanel gridPanel = new JPanel(new GridLayout(2, 2));

// Add components
topPanel.add(new JLabel("Title"));
gridPanel.add(new JButton("Button 1"));
gridPanel.add(new JButton("Button 2"));
gridPanel.add(new JButton("Button 3"));
gridPanel.add(new JButton("Button 4"));

// Combine panels
mainPanel.add(topPanel, BorderLayout.NORTH);
mainPanel.add(gridPanel, BorderLayout.CENTER);

JFrame frame = new JFrame();
frame.add(mainPanel);
frame.pack();
frame.setVisible(true);

This example shows how combining layouts can handle complex UI requirements.

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2. EVENT HANDLING

Commonly Used Listener Interfaces

1. ActionListener

Used For: Button clicks, menu item selections.
Key Method: actionPerformed(ActionEvent e)



button.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        // Code to handle the action
    }
});

2. MouseListener

Used For: Mouse events like clicks, movement, entering/exiting a component.
Key Methods:
- mouseClicked(MouseEvent e)
- mousePressed(MouseEvent e)
- mouseReleased(MouseEvent e)
- mouseEntered(MouseEvent e)
- mouseExited(MouseEvent e)


button.addMouseListener(new MouseListener() {
    public void mouseClicked(MouseEvent e) { /* Handle click */ }
    public void mousePressed(MouseEvent e) { /* Handle press */ }
    public void mouseReleased(MouseEvent e) { /* Handle release */ }
    public void mouseEntered(MouseEvent e) { /* Handle enter */ }
    public void mouseExited(MouseEvent e) { /* Handle exit */ }
});

3. KeyListener

Used For: Keyboard events like key presses.
Key Methods:
- keyPressed(KeyEvent e)
- keyReleased(KeyEvent e)
- keyTyped(KeyEvent e)


textField.addKeyListener(new KeyListener() {
    public void keyPressed(KeyEvent e) { /* Handle press */ }
    public void keyReleased(KeyEvent e) { /* Handle release */ }
    public void keyTyped(KeyEvent e) { /* Handle typed */ }
});

4. WindowListener

Used For: Window events like opening, closing, minimizing.
Key Methods:

windowClosing(WindowEvent e)
windowOpened(WindowEvent e)
windowClosed(WindowEvent e)
windowActivated(WindowEvent e)
windowDeactivated(WindowEvent e)

frame.addWindowListener(new WindowListener() {
    public void windowClosing(WindowEvent e) {
        System.out.println("Window is closing");
        System.exit(0);
    }
    // Other methods can be implemented as needed
});

Event Adapters

Purpose: Simplify event handling by providing default (empty) implementations of listener interfaces.
Common Adapters:
- MouseAdapter
- KeyAdapter
- WindowAdapter

Example Using MouseAdapter:

button.addMouseListener(new MouseAdapter() {
    public void mouseClicked(MouseEvent e) {
        System.out.println("Mouse clicked!");
    }
});



Example: Handling a Button Click

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

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

        // Register ActionListener to the button
        button.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("Button clicked!");
            }
        });

        frame.add(button);
        frame.setSize(300, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}
Event Source: JButton
Event Object: ActionEvent
Event Listener: ActionListener


3.EVENTLISTENER INTERFACE (Do it yourself)



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UNIT 2 IMP

DIPLOMA CH 1MOST IMP QUESTION (AJP)

Ch 2 link is at the bottom of the page

UNIT - 1 JAVA SWING

Commonly Used Layout Managers in Java

1. FlowLayout

2. BorderLayout

3. GridLayout

4. GridBagLayout

5. CardLayout

6. BoxLayout

Custom Layouts

Key Methods in Layout Managers

Choosing the Right Layout Manager

Best Practices for Java Layout Management

Example: Combining Layouts

Click here for more IMP AND EXAMPLES 👇

2. EVENT HANDLING

Commonly Used Listener Interfaces

1. ActionListener

2. MouseListener

3. KeyListener

4. WindowListener

Event Adapters

Example: Handling a Button Click

3.EVENTLISTENER INTERFACE (Do it yourself)

Click here for more IMP FOR SUBJECTS 👇

UNIT 2 IMP

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