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  • 1. GUI Programming in Java Tim McKenna [email_address]
  • 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 ("Swing") has components
    • Windows GUI has controls
    • Unix GUI has widgets
    • examples: labels, buttons, check boxes, radio buttons, text input boxes, pull down lists
    • Java 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
    • e.g. HelloWorldSwing.java
  • 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: JFrameDemoTM.java, JFrameDemoTM2.java, JFrameDemo.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 implemented event handlers to react to an event
  • 13. Event Handling in Java
    • the delegation event model - event listeners must be registered with an event source in order to receive notification
  • 14. Event Handling in Java
    • registration of an event listener - write a class that implements an [ event type]Listener interface - create an instance of that class (i.e. an event listener) - register the listener with a GUI component: add[event type]Listener ( <an event listener> )
  • 15. 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
  • 16. Event Handling in Java
    • different ways of coding the event listeners
    • JFrameDemoTM.java uses named inner classes.
    • JFrameDemoTM2.java uses named inner classes and shows how to consolidate window closing from two different events.
    • JFrameDemo.java does not use inner classes.