1. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 1 Chapter 12 Event-Driven Programming Chapter 11 Getting Started with GUI Programming Chapter 8 Inheritance and Polymorphism Chapter 13 Creating User Interfaces Chapter 14 Applets, Images, Audio Chapter 9 Abstract Classes and Interfaces Chapter 12 Event-Driven Programming

2. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 2 Objectives F To explain the concept of event-driven programming (§12.2). F To understand event, event source, and event classes (§12.2). F To declare listener classes and write the code to handle events (§12.3). F To register listener objects in the source object (§12.3). F To understand how an event is handled (§12.3). F To write programs to deal with ActionEvent (§12.3). F To write programs to deal with MouseEvent (§12.4). F To use the Timer class to control animations (§12.6).

3. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 3 Procedural vs. Event-Driven Programming F Procedural programming is executed in procedural order.  In event-driven programming, code is executed upon activation of events.

4. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 4 Events F An event can be defined as a type of signal to the program that something has happened. F The event is generated by external user actions such as mouse movements, mouse clicks, and keystrokes, or by the operating system, such as a timer.

5. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 5 Event Classes

6. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 6 Event Information An event object contains whatever properties are pertinent to the event. The subclasses of EventObject deal with special types of events, such as button actions, window events, component events, mouse movements, and keystrokes. Table 12.1 lists external user actions, source objects, and event types generated.

7. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 7 Selected User Actions SourceEvent Type User ActionObjectGenerated Click a button JButtonActionEvent Click a check box JCheckBoxItemEvent, ActionEvent Click a radio button JRadioButtonItemEvent, ActionEvent Press return on a text field JTextFieldActionEvent Select a new item JComboBoxItemEvent, ActionEvent Window opened, closed, etc. WindowWindowEvent Mouse pressed, released, etc. ComponentMouseEvent Key released, pressed, etc. ComponentKeyEvent

8. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 8 The Delegation Model

9. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 9 The Delegation Model: Example ListenerClass listener = new ListenerClass(); JButton jbt = new JButton("OK"); jbt.addActionListener(listener);

10. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 10 Selected Event Handlers Event ClassListener InterfaceListener Methods (Handlers) ActionEventActionListeneractionPerformed(ActionEvent) ItemEventItemListeneritemStateChanged(ItemEvent) WindowEventWindowListenerwindowClosing(WindowEvent) windowOpened(WindowEvent) windowIconified(WindowEvent) windowDeiconified(WindowEvent) windowClosed(WindowEvent) windowActivated(WindowEvent) windowDeactivated(WindowEvent) ContainerEventContainerListenercomponentAdded(ContainerEvent) componentRemoved(ContainerEvent) MouseEventMouseListenermousePressed(MouseEvent) mouseReleased(MouseEvent) mouseClicked(MouseEvent) mouseExited(MouseEvent) mouseEntered(MouseEvent) KeyEventKeyListenerkeyPressed(KeyEvent) keyReleased(KeyEvent) keyTypeed(KeyEvent)

11. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 11 java.awt.event.ActionEvent

12. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 12 Example 12.1 Handling Simple Action Events F Objective: Display two buttons OK and Cancel in the window. A message is displayed on the console to indicate which button is clicked, when a button is clicked. TestActionEvent

13. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 13 Example 12.3 Multiple Listeners for a Single Source TestMultipleListener F Objective: This example modifies Example 12.1 to add a new listener for each button. The two buttons OK and Cancel use the frame class as the listener. This example creates a new listener class as an additional listener for the action events on the buttons. When a button is clicked, both listeners respond to the action event.

14. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 14 MouseEvent

15. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 15 Handling Mouse Events  Java provides two listener interfaces, MouseListener and MouseMotionListener, to handle mouse events.  The MouseListener listens for actions such as when the mouse is pressed, released, entered, exited, or clicked.  The MouseMotionListener listens for actions such as dragging or moving the mouse.

16. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 16 Handling Mouse Events

17. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 17 Example 12.4 Moving Message Using Mouse Objective: Create a program to display a message in a panel. You can use the mouse to move the message. The message moves as the mouse drags and is always displayed at the mouse point. MoveMessageDemo

18. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 18 Example 12.5 Handling Complex Mouse Events Objective: Create a program for drawing using a mouse. Draw by dragging with the left mouse button pressed; erase by dragging with the right button pressed. ScribbleDemo

19. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 19 The Timer Class Not all source objects are GUI components. The javax.swing.Timer class is a source component that fires an ActionEvent at a predefined rate. The Timer class can be used to control animations. For example, you can use it to display a moving message. AnimationDemo

20. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 20 Clock Animation In Section 11.12, you drew a StillClock to show the current time. The clock does not tick after it is displayed. What can you do to make the clock display a new current time every second? The key to making the clock tick is to repaint it every second with a new current time. You can use a timer to control how to repaint the clock. ClockAnimation