murach’s beg. java 2, jdk 5, c17© 2005, mike murach & associates, inc.slide 1

Murach’s Beg. Java 2, JDK 5, C17 © 2005, Mike Murach & Associates, Inc. Slide 1

Chapter 17

How to handle events and validate data


Objectives

Applied

Given a class that extends JPanel and includes one or more components that generate events, modify the class so that it implements the appropriate listener interface to respond to those events.

Given a class that extends JPanel and includes one or more components that generate events, create a separate class to handle those events, and modify the panel class so that it adds the event class as a listener for each event source.

Given a class that extends JPanel and includes one or more components that generate events, add an inner class to handle the events.


Objectives (continued) Given a class that extends JPanel and includes one or more

components that generate events, add anonymous inner classes to handle the events.

Given a class that extends JPanel and includes one or more components that generate events, add event listeners to handle keyboard and focus events.

Write statements that display message dialogs using the JOptionPane class.

Given a class that extends JPanel and includes one or more text field components, add data validation to the event listeners for the panel.

Given the requirements for an application that uses the event handling and data validation techniques presented in this chapter, write the code to implement the application.


Objectives (continued) Knowledge

Distinguish among an event, an event source, and an event listener.

Explain the difference between semantic events and low-level events.

List four options for structuring the classes that implement the listener interface for an event.

List two options for structuring the classes to handle multiple event sources for a particular event.

Explain the difference between an inner class and an anonymous inner class.

Describe at least two situations in which you would want to listen to low-level events.

Explain the benefit of using adapter classes rather than implementing listener interfaces.


What happens when a button is pressed

JButton ActionListenerActionEvent

What happens when any event occurs

event source event listenerevent object


The Java event model GUI applications depend on events that represent user interactions

such as clicking a button or selecting an item from a list.

All events are represented by an event object that derives from the EventObject class. The event object contains information about the event that occurred.

An event listener is an object that responds to an event.

The class that defines an event listener must implement an event listener interface.

A component that generates an event is called an event source.

To respond to an event, an application must register an event listener object with the event source that generates the event.

The class for the event source provides a method for registering event listeners. Then, when the event occurs, the event source creates an event object and passes it to the event listener.


Semantic events

Action Event object Listener interface

Button clicked ActionEvent ActionListener

Combo box item selected ActionEvent ItemEvent

ActionListener ItemListener

List item selected ListSelectionEvent ListSelectionListener

Text component changed DocumentEvent DocumentListener

Radio button selected ActionEvent ItemEvent


Check box selected ActionEvent ItemEvent


Scroll bar repositioned AdjustmentEvent AdjustmentListener


Low-level events

Action Event object Listener interface

Window changed WindowEvent WindowListener

Focus changed FocusEvent FocusListener

Key pressed KeyEvent KeyListener

Mouse moved or clicked MouseEvent MouseListener


The two types of Java events Two types of events exist in Java: semantic events and low-level

events.

A semantic event is related to a specific component such as clicking a button or selecting an item from a list.

Low-level events are less specific, like clicking a mouse button, pressing a key on the keyboard, or closing a window.

Most events and listeners are stored in the java.awt.event package, but some of the newer events and listeners are stored in the javax.swing.event package.

Some user actions create more than one event. You can use listeners to respond to any of them.


Two steps to handle any event 1. Create a class that implements the appropriate listener interface. In

this class, you must code an implementation of the appropriate listener interface method to respond to the event.

2. Register an instance of the listener class to the event source by calling the appropriate addeventListener method


Four options for implementing the listener interface Implement it in the panel itself

Implement it in a separate class

Implement it in an inner class within the panel

Implement it in an anonymous inner class

Two options for handling multiple event sources Create one listener that handles all events for the panel

Create a separate listener for each event


Code for a panel that implements the ActionListener interface

class FutureValuePanel extends JPanel implements ActionListener { private JButton calculateButton; private JButton exitButton; public FutureValuePanel() { calculateButton = new JButton("Calculate"); calculateButton.addActionListener(this); this.add(calculateButton); exitButton = new JButton("Exit"); exitButton.addActionListener(this); this.add(exitButton); }


Code for a panel that implements the ActionListener interface (continued)

public void actionPerformed(ActionEvent e) { Object source = e.getSource(); if (source == exitButton) System.exit(0); else if (source == calculateButton) calculateButton.setText("Clicked!"); } }

Notes The easiest way to implement a listener interface is in the class

that defines the panel or frame that contains the components that generate the events.

When the panel or frame class itself implements the listener, you can specify the this keyword as the parameter to the method that registers the listener.


Code for a panel that uses a separate listener class: The panel class class FutureValuePanel extends JPanel { public JButton calculateButton; public JButton exitButton; public FutureValuePanel() { ActionListener listener = new FutureValueActionListener(this); calculateButton = new JButton("Calculate"); calculateButton.addActionListener(listener); this.add(calculateButton); exitButton = new JButton("Exit"); exitButton.addActionListener(listener); this.add(exitButton); } }


Code for a panel that uses a separate listener class: The listener class class FutureValueActionListener implements ActionListener { private FutureValuePanel panel; public FutureValueActionListener(FutureValuePanel p) { this.panel = p; } public void actionPerformed(ActionEvent e) { Object source = e.getSource(); if (source == panel.exitButton) System.exit(0); else if (source == panel.calculateButton) panel.calculateButton.setText("Clicked!"); } }


How to implement an event listener as a separate class If you implement a listener as a separate class, you’ll need to

provide a way for the listener class to access the source components and any other panel components that are required to respond to the event.

One way to do that is to pass the panel to the constructor of the listener class and declare the components that need to be referred to as public.


How to implement an event listener as an inner class An inner class is a class that is contained within another class.

An inner class has access to all of the members of its containing class. Because of that, inner classes are often used to implement event listeners.


Code that implements the listener as an inner class class FutureValuePanel extends JPanel { private JButton calculateButton; private JButton exitButton; public FutureValuePanel() { ActionListener listener = new FutureValueActionListener(); calculateButton = new JButton("Calculate"); calculateButton.addActionListener(listener); this.add(calculateButton); exitButton = new JButton("Exit"); exitButton.addActionListener(listener); this.add(exitButton); }


Code that implements the listener as an inner class (continued) class FutureValueActionListener implements ActionListener { public void actionPerformed(ActionEvent e) { Object source = e.getSource(); if (source == exitButton) System.exit(0); else if (source == calculateButton) calculateButton.setText("Clicked!"); } } }


How to implement separate event listeners for each event You can eliminate the code in the event listener class that

determines the event source by creating a separate listener class for each component that raises the event.

In that case, you simply register an instance of each event listener class with the appropriate event source.


Code that implements separate listeners for each event class FutureValuePanel extends JPanel { private JButton calculateButton; private JButton exitButton; public FutureValuePanel() { calculateButton = new JButton("Calculate"); calculateButton.addActionListener( new CalculateListener()); this.add(calculateButton); exitButton = new JButton("Exit"); exitButton.addActionListener(new ExitListener()); this.add(exitButton); }


Code that implements separate listeners for each event (continued) class CalculateListener implements ActionListener { public void actionPerformed(ActionEvent e) { calculateButton.setText("Clicked!"); } } class ExitListener implements ActionListener { public void actionPerformed(ActionEvent e) { System.exit(0); } } }


The syntax for creating an anonymous class for an event listener

new ListenerInterface() { class-body }

How to implement event listeners as anonymous inner classes An anonymous inner class is a class that is both declared and

instantiated in one statement.

Anonymous inner classes are often used as event listeners.

Anonymous inner classes force you to mix the code that creates a panel with the code that responds to the panel’s events. So they should be used for only the simplest event listeners.


Code that implements event listeners as anonymous classes class FutureValuePanel extends JPanel { private JButton calculateButton; private JButton exitButton; public FutureValuePanel() { calculateButton = new JButton("Calculate"); calculateButton.addActionListener( new ActionListener() { public void actionPerformed(ActionEvent e) { calculateButton.setText("Clicked!"); } } ); this.add(calculateButton);


Code that implements event listeners as anonymous classes (continued) exitButton = new JButton("Exit"); exitButton.addActionListener( new ActionListener() { public void actionPerformed(ActionEvent e) { System.exit(0); } } ); this.add(exitButton); } }


Common low-level events and listeners Event Interface Methods

Moving the focus

FocusListener void focusLost(FocusEvent e) void focusLost(FocusEvent e)

Pressing or releasing a key

KeyListener void keyPressed(KeyEvent e) void keyReleased(KeyEvent e) void keyTyped(KeyEvent e)

Moving or dragging the mouse

MouseMotionListener void mouseDragged(MouseEvent e) void mouseMoved(MouseEvent e)

Clicking the mouse

MouseListener void mouseClicked(MouseEvent e) void mouseEntered(MouseEvent e) void mouseExited(MouseEvent e) void mousePressed(MouseEvent e) void mouseReleased(MouseEvent e)


Common low-level events and listeners (continued) Event Interface Methods

Moving or sizing a component

ComponentListener void componentHidden(ComponentEvent e) void componentMoved(ComponentEvent e) void componentResized(ComponentEvent e) void componentShown(ComponentEvent e)

Working with the window

WindowListener void windowActivated(WindowEvent e) void windowClosed(WindowEvent e) void windowClosing(WindowEvent e) void windowDeactivated(WindowEvent e) void windowDeiconified(WindowEvent e) void windowIconified(WindowEvent e) void windowOpened(WindowEvent e)


Methods that add low-level listeners

Event source Method

Component addFocusListener(FocusListener)

Component addKeyListener(KeyListener)

Component addMouseMotionListener(MouseMotionListener)

Component addMouseListener(MouseListener)

Component addComponentListener(ComponentListener)

Window addWindowListener(WindowListener)


How to work with focus events A focus event occurs when the focus moves to or from a component.

To implement a focus listener, you must implement both of the methods of the FocusListener interface.

Methods of the FocusListener interface

Method Description void focusGained( FocusEvent e)

Invoked when a component that implements a focus listener gains the focus.

void focusLost( FocusEvent e)

Invoked when a component that implements a focus listener loses the focus.


Common methods of the FocusEvent class

Method Description

getComponent() Returns the component where the event occurred.

isTemporary() Returns true if the focus is a temporary change.

getOppositeComponent() Returns the other component involved in the focus change. Introduced with JDK 1.4.

A method of the JTextComponent class

Method Description

selectAll() Selects all of the text in the text component.


A class that implements the FocusListener interface

public class AutoSelect implements FocusListener { public void focusGained(FocusEvent e) { if (e.getComponent() instanceof JTextField) { JTextField t = (JTextField) e.getComponent(); t.selectAll(); } } public void focusLost(FocusEvent e) {} }

A text field that uses the focus listener paymentTextField = new JTextField(10); paymentTextField.addFocusListener(new AutoSelect()); displayPanel.add(paymentTextField);


How to work with keyboard events A keyboard event occurs when a user presses, releases, or presses

and releases a key.

The KeyEvent class inherits the InputEvent class.

Methods of the KeyListener interface

Method Description

void keyPressed(KeyEvent e) Invoked when a key is pressed.

void keyReleased(KeyEvent e) Invoked when a key is released.

void keyTyped(KeyEvent e) Invoked when a key is pressed and released.


Common methods of the KeyEvent class

Method Description

getKeyCode() Returns an int code that represents the key pressed.

getKeyChar() Returns a char that represents the key pressed.

isControlDown() Returns a boolean that indicates if the Ctrl key is down.

isAltDown() Returns a boolean that indicates if the Alt key is down.

isShiftDown() Returns a boolean that indicates if the Shift key is down.

A method of the InputEvent class

Method Description

consume() Stops further processing of the event.


A class that implements the KeyListener interface public class NumFilter implements KeyListener { public void keyTyped(KeyEvent e) { char c = e.getKeyChar(); if ( c != '0' && c != '1' && c != '2' && c != '3' && c != '4' && c != '5' && c != '6' && c != '7' && c != '8' && c != '9' && c != '.' && c != '+' && c != '-') e.consume(); } public void keyPressed(KeyEvent e) {} public void keyReleased(KeyEvent e) {} }


A text field that uses the key listener paymentTextField = new JTextField(10); paymentTextField.addKeyListener(new NumFilter()); displayPanel.add(paymentTextField);


How to work with adapter classes An adapter class is a class that implements all the methods of a

listener interface as empty methods. Then, an event listener class that inherits an adapter class must override only the methods that the program needs.

Common adapter classes

Class Interface

WindowAdapter WindowListener

FocusAdapter FocusListener

KeyAdapter KeyListener

MouseAdapter MouseListener

MouseMotionAdapter MouseMotionListener


The AutoSelect class using FocusAdapter public class AutoSelect extends FocusAdapter { public void focusGained(FocusEvent e) { if (e.getComponent() instanceof JTextField) { JTextField t = (JTextField) e.getComponent(); t.selectAll(); } } }


The NumFilter class using KeyAdapter public class NumFilter extends KeyAdapter { public void keyTyped(KeyEvent e) { char c = e.getKeyChar(); if ( c != '0' && c != '1' && c != '2' && c != '3' && c != '4' && c != '5' && c != '6' && c != '7' && c != '8' && c != '9' && c != '.' && c != '+' && c != '-') e.consume(); } }


An error message displayed in a JOptionPane dialog box


The showMessageDialog method of the JOptionPane class

Syntax showMessageDialog(parentComponent, messageString, titleString, messageTypeInt);

Arguments

Argument Description

parentComponent An object representing the component that’s the parent of the dialog box.

messageString A string representing the message to be displayed in the dialog box.

titleString A string representing the title of the dialog box.

messageTypeInt An int that indicates the type of icon that will be used for the dialog box.


Fields used for the message type parameter

Icon displayed Field

(none) PLAIN_MESSAGE

INFORMATION_MESSAGE

WARNING_MESSAGE

ERROR_MESSAGE

QUESTION_MESSAGE

How to display error messages The showMessageDialog method is a static method of the

JOptionPane class that is commonly used to display dialog boxes with error messages for data validation.

You can also use the JOptionPane class to accept input from the user.


Code that displays the Invalid Entry dialog box String message = "Monthly Investment is a required field.\n" + "Please re-enter."; JOptionPane.showMessageDialog(this, // assumes "this" is a component message, "Invalid Entry", JOptionPane.ERROR_MESSAGE);


How to validate the data entered into a text field Like console applications, Swing applications should validate all

data entered by the user before processing the data.

When an entry is invalid, the program needs to display an error message and give the user another chance to enter valid data.

To test whether a value has been entered into a text field, you can use the getText method of the text field to get a string that contains the text the user entered. Then, you can check whether the length of that string is zero by using its length method.

To test whether a text field contains valid numeric data, you can code the statement that converts the data in a try block and use a catch block to catch a NumberFormatException.


Code that checks if an entry has been made if (investmentTextField.getText().length() == 0) { JOptionPane.showMessageDialog(this, "Monthly Investment is " + "a required field.\nPlease re-enter.", "Invalid Entry", JOptionPane.ERROR_MESSAGE); investmentTextField.requestFocusInWindow(); validData = false; }


Code that checks if an entry is a valid number try { double d = Double.parseDouble( investmentTextField.getText()); } catch (NumberFormatException e) { JOptionPane.showMessageDialog(this, "Monthly Investment " + "must be a valid number.\nPlease re-enter.", "Invalid Entry", JOptionPane.ERROR_MESSAGE); investmentTextField.requestFocusInWindow(); validData = false; }


The code for the SwingValidator class import javax.swing.*; import javax.swing.text.JTextComponent; public class SwingValidator { public static boolean isPresent(JTextComponent c, String title) { if (c.getText().length() == 0) { showMessage(c, title + " is a required field.\n" + "Please re-enter."); c.requestFocusInWindow(); return false; } return true; }


The code for the SwingValidator class (continued) public static boolean isInteger(JTextComponent c, String title) { try { int i = Integer.parseInt(c.getText()); return true; } catch (NumberFormatException e) { showMessage(c, title + " must be an integer.\n" + "Please re-enter."); c.requestFocusInWindow(); return false; } }


The code for the SwingValidator class (continued) public static boolean isDouble(JTextComponent c, String title) { try { double d = Double.parseDouble(c.getText()); return true; } catch (NumberFormatException e) { showMessage(c, title + " must be a valid number.\n" + "Please re-enter."); c.requestFocusInWindow(); return false; } } private static void showMessage(JTextComponent c, String message) { JOptionPane.showMessageDialog(c, message, "Invalid Entry", JOptionPane.ERROR_MESSAGE); } }


How to validate multiple entries When more than one field needs to be validated, it is best to put

all the validation logic in a separate method that returns a boolean value to indicate whether or not the data is valid.


Code that validates multiple entries with a series of if statements public boolean isValidData() { // validate investmentTextField if (!SwingValidator.isPresent(investmentTextField, "Monthly Investment")) return false; if (!SwingValidator.isDouble(investmentTextField, "Monthly Investment")) return false; // validate rateTextField if (!SwingValidator.isPresent(rateTextField, "Interest Rate")) return false; if (!SwingValidator.isDouble(rateTextField, "Interest Rate")) return false; // validate yearsTextField if (!SwingValidator.isPresent(yearsTextField, "Number of Years")) return false; if (!SwingValidator.isInteger(yearsTextField, "Number of Years")) return false; return true; }


Code that validates multiple entries with a compound condition public boolean isValidData() { return SwingValidator.isPresent(investmentTextField, "Monthly Investment") && SwingValidator.isDouble(investmentTextField, "Monthly Investment") && SwingValidator.isPresent(rateTextField, "Interest Rate") && SwingValidator.isDouble(rateTextField, "Interest Rate") && SwingValidator.isPresent(yearsTextField, "Number of Years") && SwingValidator.isInteger(yearsTextField, "Number of Years"); }


Code that calls the isValidData method from an action event listener public void actionPerformed(ActionEvent e) { Object source = e.getSource(); if (source == calculateButton) { if (isValidData()) { // code that processes the data } } }


The Product Maintenance frame


Typical dialog boxes displayed when invalid data is entered in the Product Maintenance application


The Product Maintenance application import java.awt.*; import java.awt.event.*; import javax.swing.*; import java.util.ArrayList; public class ProductMaintenanceApp { public static void main(String[] args) { JFrame frame = new ProductMaintenanceFrame(); frame.setVisible(true); } } class ProductMaintenanceFrame extends JFrame { public ProductMaintenanceFrame() { setTitle("Product Display"); setResizable(false); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); this.add(new ProductMaintenancePanel()); this.pack(); centerWindow(this); }


The Product Maintenance application (continued) private void centerWindow(Window w) { Toolkit tk = Toolkit.getDefaultToolkit(); Dimension d = tk.getScreenSize(); setLocation((d.width-w.getWidth())/2, (d.height-w.getHeight())/2); } } class ProductMaintenancePanel extends JPanel { ProductDAO productDAO; ArrayList<Product> products; Product newProduct = null; ProductSelectorPanel selectorPanel; ProductDisplayPanel productPanel; ProductButtonPanel buttonPanel;


The Product Maintenance application (continued) public ProductMaintenancePanel() { // fill the products ArrayList productDAO = DAOFactory.getProductDAO(); products = productDAO.getProducts(); // add the panels setLayout(new GridBagLayout()); selectorPanel = new ProductSelectorPanel(); add(selectorPanel, getConstraints( 0,0,1,1, GridBagConstraints.EAST)); productPanel = new ProductDisplayPanel(); add(productPanel, getConstraints( 0,1,1,1, GridBagConstraints.EAST)); buttonPanel = new ProductButtonPanel(); add(buttonPanel, getConstraints( 0,2,1,1, GridBagConstraints.EAST)); // set the initial product to be displayed productPanel.showProduct(products.get(0)); selectorPanel.selectProduct(products.get(0)); }


The Product Maintenance application (continued) // a method for setting grid bag constraints private GridBagConstraints getConstraints(int gridx, int gridy, int gridwidth, int gridheight, int anchor) { GridBagConstraints c = new GridBagConstraints(); c.insets = new Insets(5, 5, 5, 5); c.ipadx = 0; c.ipady = 0; c.gridx = gridx; c.gridy = gridy; c.gridwidth = gridwidth; c.gridheight = gridheight; c.anchor = anchor; return c; } class ProductSelectorPanel extends JPanel implements ActionListener { public JComboBox productComboBox; private JLabel productLabel;


The Product Maintenance application (continued) boolean filling = false; // used to indicate the // combo box is being filled public ProductSelectorPanel() { // set panel layout setLayout(new FlowLayout(FlowLayout.LEFT)); // product label productLabel = new JLabel("Select Product:"); add(productLabel); // product combo box productComboBox = new JComboBox(); fillComboBox(products); productComboBox.addActionListener(this); add(productComboBox); }


The Product Maintenance application (continued) public void actionPerformed(ActionEvent e) { if (!filling) { Product p = (Product)productComboBox.getSelectedItem(); productPanel.showProduct(p); } } public void fillComboBox(ArrayList<Product> a) { filling = true; productComboBox.removeAllItems(); for (Product p : a) productComboBox.addItem(p); filling = false; } public void selectProduct(Product p) { productComboBox.setSelectedItem(p); }


The Product Maintenance application (continued) public Product getCurrentProduct() { return (Product) productComboBox.getSelectedItem(); } } class ProductDisplayPanel extends JPanel { public JTextField codeTextField, descriptionTextField, priceTextField; private JLabel codeLabel, descriptionLabel, priceLabel; public ProductDisplayPanel() { // set panel layout setLayout(new GridBagLayout());


The Product Maintenance application (continued) // code label codeLabel = new JLabel("Product Code:"); add(codeLabel, getConstraints( 0,0,1,1, GridBagConstraints.EAST));

// code text field codeTextField = new JTextField(10); codeTextField.setEditable(false); codeTextField.setFocusable(false); codeTextField.addFocusListener(new AutoSelect()); add(codeTextField, getConstraints( 1,0,1,1, GridBagConstraints.WEST));

// description label descriptionLabel = new JLabel("Desription:"); add(descriptionLabel, getConstraints( 0,1,1,1, GridBagConstraints.EAST));

// description text field descriptionTextField = new JTextField(30); descriptionTextField.setEditable(false); descriptionTextField.setFocusable(false); descriptionTextField.addFocusListener(new AutoSelect()); add(descriptionTextField, getConstraints( 1,1,1,1, GridBagConstraints.WEST));


The Product Maintenance application (continued) // price label priceLabel = new JLabel("Unit Price:"); add(priceLabel, getConstraints( 0,2,1,1, GridBagConstraints.EAST)); // price text field priceTextField = new JTextField(10); priceTextField.setEditable(false); priceTextField.setFocusable(false); priceTextField.addFocusListener(new AutoSelect()); priceTextField.addKeyListener(new NumFilter()); add(priceTextField, getConstraints( 1,2,1,1, GridBagConstraints.WEST)); } public void showProduct(Product p) { codeTextField.setText(p.getCode()); descriptionTextField.setText(p.getDescription()); priceTextField.setText(p.getFormattedPrice()); }


The Product Maintenance application (continued) public void clearFields() { codeTextField.setText(""); descriptionTextField.setText(""); priceTextField.setText(""); } // return a Product object with the data in the text fields public Product getProduct() { Product p = new Product(); p.setCode(codeTextField.getText()); p.setDescription(descriptionTextField.getText()); p.setPrice(Double.parseDouble( priceTextField.getText())); return p; } public void setAddMode() { codeTextField.setEditable(true); codeTextField.setFocusable(true); codeTextField.requestFocusInWindow(); descriptionTextField.setEditable(true);


The Product Maintenance application (continued) descriptionTextField.setFocusable(true); priceTextField.setEditable(true); priceTextField.setFocusable(true); } public void setEditMode() { descriptionTextField.setEditable(true); descriptionTextField.setFocusable(true); descriptionTextField.requestFocusInWindow(); priceTextField.setEditable(true); priceTextField.setFocusable(true); } public void setDisplayMode() { codeTextField.setEditable(false); codeTextField.setFocusable(false); descriptionTextField.setEditable(false); descriptionTextField.setFocusable(false); priceTextField.setEditable(false); priceTextField.setFocusable(false); } }


The Product Maintenance application (continued) class ProductButtonPanel extends JPanel { public JButton addButton, editButton, deleteButton, acceptButton, cancelButton, exitButton; public ProductButtonPanel() { // create maintenance button panel JPanel maintPanel = new JPanel(); maintPanel.setLayout(new FlowLayout(FlowLayout.CENTER)); // add button addButton = new JButton("Add"); addButton.addActionListener(new AddListener()); maintPanel.add(addButton); // edit button editButton = new JButton("Edit"); editButton.addActionListener(new EditListener()); maintPanel.add(editButton);


The Product Maintenance application (continued) // delete button deleteButton = new JButton("Delete"); deleteButton.addActionListener(new DeleteListener()); maintPanel.add(deleteButton); // accept button acceptButton = new JButton("Accept"); acceptButton.setEnabled(false); acceptButton.addActionListener(new AcceptListener()); maintPanel.add(acceptButton); // cancel button cancelButton = new JButton("Cancel"); cancelButton.setEnabled(false); cancelButton.addActionListener(new CancelListener()); maintPanel.add(cancelButton); // create exit button panel JPanel exitPanel = new JPanel(); exitPanel.setLayout(new FlowLayout(FlowLayout.RIGHT));


The Product Maintenance application (continued) // exit button exitButton = new JButton("Exit"); exitButton.addActionListener(new ExitListener()); exitPanel.add(exitButton); // add panels to the ProductButtonPanel setLayout(new BorderLayout()); add(maintPanel, BorderLayout.CENTER); add(exitPanel, BorderLayout.SOUTH); } public void setAddEditMode(boolean e) { addButton.setEnabled(!e); editButton.setEnabled(!e); deleteButton.setEnabled(!e); acceptButton.setEnabled(e); cancelButton.setEnabled(e); } }


The Product Maintenance application (continued) class AddListener implements ActionListener { public void actionPerformed(ActionEvent e) { newProduct = new Product(); productPanel.clearFields(); buttonPanel.setAddEditMode(true); productPanel.setAddMode(); } } class EditListener implements ActionListener { public void actionPerformed(ActionEvent e) { buttonPanel.setAddEditMode(true); productPanel.setEditMode(); } }


The Product Maintenance application (continued) class DeleteListener implements ActionListener { public void actionPerformed(ActionEvent e) { Product p = productPanel.getProduct(); productDAO.deleteProduct(p); products.remove(p); selectorPanel.fillComboBox(products); selectorPanel.selectProduct(products.get(0)); productPanel.showProduct(products.get(0)); selectorPanel.productComboBox.requestFocusInWindow(); } } class AcceptListener implements ActionListener { public void actionPerformed(ActionEvent e) { if (isValidData()) { if (newProduct != null) { newProduct = productPanel.getProduct(); productDAO.addProduct(newProduct);


The Product Maintenance application (continued) products.add(newProduct); selectorPanel.fillComboBox(products); selectorPanel.selectProduct(newProduct); newProduct = null; } else { Product p = selectorPanel.getCurrentProduct(); Product newProduct = productPanel.getProduct(); p.setDescription(newProduct.getDescription()); p.setPrice(newProduct.getPrice()); productDAO.updateProduct(p); selectorPanel.fillComboBox(products); selectorPanel.selectProduct(p); productPanel.showProduct( selectorPanel.getCurrentProduct()); } productPanel.setDisplayMode(); buttonPanel.setAddEditMode(false); selectorPanel.productComboBox.requestFocusInWindow(); } }


The Product Maintenance application (continued) public boolean isValidData() { if (newProduct != null) return SwingValidator.isPresent( productPanel.codeTextField, "Product Code") && SwingValidator.isPresent( productPanel.descriptionTextField, "Description") && SwingValidator.isPresent( productPanel.priceTextField, "Unit Price") && SwingValidator.isDouble( productPanel.priceTextField, "Unit Price"); else return SwingValidator.isPresent( productPanel.descriptionTextField, "Description") && SwingValidator.isPresent( productPanel.priceTextField, "Unit Price") && SwingValidator.isDouble( productPanel.priceTextField, "Unit Price"); } }


The Product Maintenance application (continued) class CancelListener implements ActionListener { public void actionPerformed(ActionEvent e) { if (newProduct != null) { newProduct = null; } productPanel.setDisplayMode(); productPanel.showProduct( selectorPanel.getCurrentProduct()); buttonPanel.setAddEditMode(false); selectorPanel.productComboBox.requestFocusInWindow(); } } class ExitListener implements ActionListener { public void actionPerformed(ActionEvent e) { System.exit(0); } } }

murach’s beg. java 2, jdk 5, c17© 2005, mike murach & associates, inc.slide 1

Documents