1. Review: Java GUI Programming
R.E. Johnson, Frameworks=(Components + Patterns), CACM, 4(10):39-42, October 1997.
J. Elliott, et al., Java Swing, 2nd edition, O’Reilly,

2. Outline Frameworks MVC model Elements of GUI frameworks
GUI components (views and widgets)
Layout managers
Handling events
Lab: Timer applet

3. Object-Oriented Framework
A set of cooperating (abstract) classes and interface that:
Represent reusable designs of software systems in a particular application domain,
Provide semi-complete applications that can be specialized to produce custom applications, and
Defines conventions for extending the abstract classes, implementing the interfaces, and allowing their instances to interact with one another

4. Examples GUI Small Network/Distributed/Web Applets, …
AWT, Swing, SWT (Eclipse)
MFC, …
Network/Distributed/Web
RMI, J2EE, CORBA, Drupal (PHP), …

5. Why Frameworks? Benefits
To support reuse of design and implementations in particular application domains
Benefits
Quick and easy application development
Reliable application (i.e., high confidence)
Standardized applications

6. Characteristics of Frameworks
Extensibility
Inversion of control
Design patterns as building blocks
Code written by
programmer
Library code
Application
(master)
Component
(slave)
Library-based
Framework
code
Code written
by programmer
Framework-based

7. Outline Frameworks MVC model Elements of GUI frameworks
GUI components (views and widgets)
Layout managers
Handling events
Lab: Timer applet

8. GUI Framework in General
MVC metaphor for separation of concerns
Event-based, implicit invocation style
Single vs. multithreading

9. MVC Metaphor A way of cleanly breaking an application into three parts
Model for maintaining data,
View for displaying all or a portion of the data, and
Controller for handling events that affect the model or views.
View
Controller
Model

10. Separating M from VC View Controller Model changes get data
from model
changes
model or view
View
Controller
Model
update view
when data changes

11. Due to Separation … Multiple views and controllers for models.
New views and controllers can be added for the model.
Changes in views are localized; such changes have minimal or no impact on the model.

12. Outline Frameworks MVC model Elements of GUI frameworks
GUI components (views and widgets)
Layout managers
Handling events
Lab: Timer applet

13. GUI Framework Classes GUI components (views and widgets)
JButton, JLabel, JTextField, JPanel, …
Layout managers
FlowLayout, BorderLayout, GridBagLayout, …
Events and event listeners
ActionEvent, ActionListener, …
Graphics, imaging, and other multimedia classes

14. Event Handling Mechanism to write control code Composed of: Event
Event source
Event listener (or handler)

15. Event Handling (Cont.) Event Event source
A way for GUI components to communicate with the rest of application
Implemented as event classes (e.g., ActionEvent)
Event source
Components generating events
Examples: buttons, check boxes, combo boxes, etc.

16. Event Handling (Cont.) Event listener (or handler)
Objects that receives and processes events
Must implement an appropriate listener interface
Must inform the source its interest in handling a certain type of events (by registering)
May listen to several sources and different types of events

17. Example // create a button JButton button = new JButton(“Start”);
// register an action listener
button.addActionListener(new StartButtonActionListener());
// Action listener class
class StartButtonActionListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
// handle the event e …
System.out.println(“Start button pressed!”); }

18. Using Anonymous Class // create a button
JButton button = new JButton(“Start”);
// register an action listener
button.addActionListener(new ActionListener {
public void actionPerformed(ActionEvent e) {
// handle the event e …
System.out.println(“Start button pressed!”); }
});

19. Using Lambda Notation (Java 8)
// create a button
JButton button = new JButton(“Start”);
// register an action listener
button.addActionListener(e -> {
// handle the event e …
System.out.println(“Start button pressed!”);
});

20. Example (Cont.) b: JButton h: ActionListener addActionListener(h)
<<create>>
e: ActionEvent
actionPerformed(e)
Observer design pattern
getSource()

21. Lab (Pair): Timer Applet
Write a timer applet incrementally (see handout)
Use MVC by defining a model class, say TimerModel.
init
destroy
start
stop
Applet lifecycle
public class TimerApplet extends JApplet {
private final TimerModel timerModel = new TimerModel();
public void init() { /* configure UI. */ } }