1. GUI Programming in Java
Tim McKenna

2. GUI Programming Concepts
conventional programming:
sequence of operations is determined by the program
what you want to happen, happens when you want it
event-driven programming:
sequence of operations is determined by the user’s interaction with the application’s interface
anything that can happen, happens at any time

3. GUI Design Concepts
a wealth of information creates a poverty of attention - Herbert Simon
Principles of good GUI Design
IBM's Design concepts
Saul Greenberg's HCI pages
Tim's HCI notes

4. GUI Programming Concepts in Java
Java GUI has components
Windows GUI has controls
Unix GUI has widgets
examples: labels, buttons, check boxes, radio buttons, text input boxes, pull down lists
Swing components: JLabel, JButton, JCheckBox, JRadioButton, JTextField, JTextArea, JComboBox

5. Java GUI history: the AWT
AWT(JDK 1.0, 1.1): Abstract Window Toolkit
package: java.awt, java.awt.event
heavyweight components using native GUI system elements
used for applets until most browsers supported JRE 1.2

6. Swing in Java
Swing(Java 2, JDK 1.2+)
lightweight components that do not rely on the native GUI or OS
“look and feel” of Swing components
are identical on different platforms
can be customized
Swing inherits from AWT
AWT still used for events, layouts

7. Swing Components in Java
advanced GUI support. e.g. drag-and-drop
package names: javax.swing, javax.swing.event
components inherit from JComponent
components are added to a top-level container: JFrame, JDialog, or JApplet.

8. running a Swing application
java -Dswing.aatext=true MySwingClass
the option sets the system property "swing.aatext" to "true" to enable anti-aliasing for every JComponent
javaw runs a GUI without the console window

9. Basic GUI Programming Steps in Java
declare a container and components
add components to one or more containers using a layout manager
register event listener(s) with the components
create event listener method(s)

10. Basic GUI Programming Concepts in Java
Example: JFrameDemo.java, JFrameDemoTM.java
container : a screen window/applet window/panel that groups and arranges GUI components
GUI component: an object with visual representation
Swing containers: JFrame, JApplet, JPanel
AWT containers: Frame, Applet, Panel

11. GUI Programming: The Java Approach
event-driven programming
a piece of code (i.e. event handler) is attached to a GUI component
an event handler is called when an event (e.g. a mouse click) is activated / fired
The Delegation Event Model in Java
processing of an event is delegated to an object (the listener) in the program

12. Event-driven Programming in Java
event source: a GUI component that generates / fires an event
event: a user interaction (e.g. a click on the button)
event listener: an object that has encapsulated event handlers to react to an event

13. Event Handling in Java
the delegation event model - a GUI element “delegates” the processing of an event to another piece of code (i.e. an event handler) the event source generates/fires an event and “sends” it to event listeners

14. Event Handling in Java
the delegation event model - event listeners must be registered with an event source in order to receive notification
Example: JButtonDemo.java, JButtonDemo2.java

15. Event Handling in Java
registration of an event listener - write a class that implements an <event name>Listener interface create an instance of that class (i.e. an event listener) register the listener with a GUI component: add<event name>Listener ( <an event listener> )

16. Event Handling in Java
a listener interface has a list of standard event handlers (i.e. methods)
API documentation java.awt.event event classes listener interfaces adapter classes

17. Event Handling in Java
different ways of coding the event listeners use of another top-level class: JButtonDemo - anonymous inner classes: JButtonDemo2, JFrameDemo, JFrameDemo2 - use of an adapter class: JFrameDemo3
JFrameDemoTM2.java uses named inner classes and shows how to consolidate window closing from two different events.

18. Handling of Mouse Events
MouseListener mousePressed( ), mouseClicked( ) mouseReleased( ), mouseEntered( ) mouseExited( )
MouseMotionListener mouseDragged( ), mouseMoved( )
MouseAdapter, MouseMotionAdapter
Example: MouseDemo.java

19. Multiple Event Sources
Example: ActionApplet2.java & .html
one listener for multiple event sources
GUI and graphics programming