Module 4: Java Swing GUI Programming

// Create a label with text (like a sticker with words on it)
// Users can SEE this text but can't change it
JLabel label = new JLabel("Hello, World!");

// Add the label to our window
frame.add(label);

// Create a button with text on it
// Users can click this to do something
JButton button = new JButton("Click Me");

// Add the button to our window
frame.add(button);

// Create a text input box
// 20 = width (can hold about 20 characters)
JTextField textField = new JTextField(20);
frame.add(textField);

// Get whatever text the user typed
String text = textField.getText();

// Put text into the field (program fills it)
textField.setText("Hello");

// Create a multi-line text box
// 10 = number of rows (lines), 30 = number of columns (width)
JTextArea textArea = new JTextArea(10, 30);

// Wrap text area in a scroll pane
// This adds scrollbars if text is too long
JScrollPane scrollPane = new JScrollPane(textArea);

// Add the scroll pane (which contains the text area) to window
frame.add(scrollPane);

// Create a password field (text appears as ••• for security)
JPasswordField passwordField = new JPasswordField(20);
frame.add(passwordField);

// Get the password (returns char array for security)
char[] passwordChars = passwordField.getPassword();

// Convert to String if needed
String password = new String(passwordChars);

// Create checkboxes (user can check multiple)
JCheckBox checkbox1 = new JCheckBox("Option 1");
JCheckBox checkbox2 = new JCheckBox("Option 2");
JCheckBox checkbox3 = new JCheckBox("Option 3", true); // true = checked by default

frame.add(checkbox1);
frame.add(checkbox2);
frame.add(checkbox3);

// Check if a checkbox is selected
if (checkbox1.isSelected()) {
    System.out.println("Option 1 is checked");
}

// Create radio buttons (only one can be selected at a time)
JRadioButton option1 = new JRadioButton("Small");
JRadioButton option2 = new JRadioButton("Medium");
JRadioButton option3 = new JRadioButton("Large");

// Group them together (ensures only one can be selected)
ButtonGroup group = new ButtonGroup();
group.add(option1);
group.add(option2);
group.add(option3);

// Add to frame
frame.add(option1);
frame.add(option2);
frame.add(option3);

// Check which one is selected
if (option1.isSelected()) {
    System.out.println("Small selected");
}

// Create a drop-down list with options
String[] options = {"Red", "Green", "Blue", "Yellow"};
JComboBox comboBox = new JComboBox<>(options);
frame.add(comboBox);

// Get selected item
String selected = (String) comboBox.getSelectedItem();

// Add action listener to detect when user selects something
comboBox.addActionListener(e -> {
    String choice = (String) comboBox.getSelectedItem();
    System.out.println("User selected: " + choice);
});

// Create a panel to group related components
JPanel panel = new JPanel();
panel.setLayout(new FlowLayout());

// Add components to the panel (not directly to frame)
panel.add(new JLabel("Name:"));
panel.add(new JTextField(15));
panel.add(new JButton("Submit"));

// Add the entire panel to the frame
frame.add(panel);

// Panels are useful for organizing complex layouts
// You can have multiple panels with different layouts

// Show a simple message
JOptionPane.showMessageDialog(null, "Hello, World!");

// Show a confirmation dialog (Yes/No)
int result = JOptionPane.showConfirmDialog(null, "Are you sure?");
if (result == JOptionPane.YES_OPTION) {
    System.out.println("User clicked Yes");
}

// Ask for input
String name = JOptionPane.showInputDialog("Enter your name:");

// Show error message
JOptionPane.showMessageDialog(null, "Error!", "Error", JOptionPane.ERROR_MESSAGE);