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GUI Programming in Java

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Presentation on theme: "GUI Programming in Java"— Presentation transcript:

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:, 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:,

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 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:

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

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