1. Graphical User Interface Components: Part 1
Chapter 11

2. What You Will Learn Swing Components Event handling
Mouse event handling

3. Graphical User Interface (GUI)
Gives program distinctive “look” and “feel”
Provides users with basic level of familiarity
Built from GUI components (controls, widgets, etc.)
User interacts with GUI component via mouse, keyboard, etc
Check out this visual index of components

4. Netscape Window With GUI Components
menu bar
button
combo box
menus
scroll bars

5. Dialog Boxes Used by applications to interact with the user
Provided by Java’s JOptionPane class
Contains input dialogs and message dialogs
View example program, Figure 11.2
Text field which allows user input
Title Bar
Prompt to user
When user clicks OK, dialog box dismissed

6. Dialog Boxes
Note icon
Other icons available

7. Some Basic GUI Components

8. Overview Swing GUI components Abstract Window Toolkit (AWT)
Declared in package javax.swing
Most are pure Java components
Part of the Java Foundation Classes (JFC)
Abstract Window Toolkit (AWT)
Precursor to Swing
Declared in package java.awt
Does not provide consistent, cross-platform look-and-feel

9. Lightweight vs. Heavyweight
Lightweight components
Not tied directly to GUI components supported by underlying platform
Heavyweight components
Tied directly to the local platform
AWT components
Some Swing components

10. Superclasses of Swing’s Lightweight GUI Components
Class Component
(package java.awt)
Subclass of Object
Declares many behaviors and attributes common to GUI components

11. Superclasses of Swing’s Lightweight GUI Components
Class Container
(package java.awt)
Subclass of Component
Organizes Components

12. Superclasses of Swing’s Lightweight GUI Components
Class JComponent
(package javax.swing)
Subclass of Container
Superclass of all lightweight Swing components

13. Common Lightweight Component Features
Pluggable look-and-feel
customize the appearance of components
Shortcut keys
mnemonics
Common event-handling capabilities
Brief description of component’s purpose
tool tips
Support for localization

14. Displaying Text and Images in a Window
Class JFrame
Most windows are an instance or subclass of this class
Provides title bar
Provides min, max, close buttons
Label
Text instructions or information stating the purpose of each component
Created with class JLabel

15. Three Parts of a GUI Application
Components that make up the Graphical User Interface
Listeners that receive the events and respond to them
Application code that does useful work for the user

16. Events Generated by Swing Components
Act that results in the event
Listener type
User clicks a button, presses Return while typing in a text field, or chooses a menu item
ActionListener
User closes a frame (main window)
WindowListener
User presses a mouse button while the cursor is over a component
MouseListener
User moves the mouse over a component
MouseMotionListener
Component becomes visible
ComponentListener
Component gets the keyboard focus
FocusListener
Table or list selection changes
ListSelectionListener

17. Events Generated by Swing Components
Each event is represented by an object
Object gives information about the event
Identifies the event source.
Event sources are typically components,
Other kinds of objects can also be event sources.
Each event source can have multiple listeners registered on it.
Conversely, a single listener can register with multiple event sources.

18. JLabel Label View Figure 11.6 Provide text on GUI
Defined with class JLabel
Can display:
Single line of read-only text
Image
Text and image
View Figure 11.6
Note uses of the JLabel Class

19. Creating and Attaching label1
Method setToolTipText of class JComponent
Specifies the tool tip
Method add of class Container
Adds a component to a container

20. Creating and Attaching label2
Interface Icon
Can be added to a JLabel with the setIcon method
Implemented by class ImageIcon

21. Creating and Attaching label2
Interface SwingConstants
Declares a set of common integer constants such as those used to set the alignment of components
Can be used with methods setHorizontalAlignment and setVerticalAlignment

22. Creating and Attaching label3
Other JLabel methods
getText and setText
For setting and retrieving the text of a label
getIcon and setIcon
For setting and retrieving the icon displayed in the label
getHorizontalTextPosition and setHorizontalTextPosition
For setting and retrieving the horizontal position of the text displayed in the label

23. Some basic GUI Components.

24. Other JFrame Methods setDefaultCloseOperation setSize setVisible
Dictates how the application reacts when the user clicks the close button
setSize
Specifies the width and height of the window
setVisible
Determines whether the window is displayed (true) or not (false)

25. Event Handling An event occurs every time the user
Types a character or
Pushes a mouse button
Any object can be notified of the event.
That object must:
Implement the appropriate interface
Be registered as an event listener on the appropriate event source.

26. Event Handling GUI's are event driven Class java.awt.AWTEvent
Events occur when user interacts with GUI
e.g., moving mouse, pressing button, typing in text field, etc.
Class java.awt.AWTEvent
Checkout Sun tutorial on event handling

27. Some Event Classes Of Package java.awt.event

28. Event Handling Model Three parts Programmer must perform two tasks
Event source
GUI component with which user interacts
Event object
Encapsulates information about event that occurred
Event listener
Receives event object when notified, then responds
Programmer must perform two tasks
Register event listener for event source
Implement event-handling method (event handler)

29. Event Listener Object
When a GUI program is running, each action of the user generates an event
The following are some types of events:
Moving the mouse
Clicking the mouse on a button
Typing some text into a text area
For a program to respond to an event there must be an event listener object in the GUI program that listens to that type of event

30. What is an Event Listener?
An event listener is an object
It "listens" for events from a specific GUI component (itself an object)
When an event is generated by the GUI component
A method in the listener object is invoked to respond to the event

31. What If …? When there is no event listener for an event
When a tree falls in the forest and there's no one present to hear it, does it make a sound?
When there is no event listener for an event
A program can ignore events
If there is no listener for an event, the event is just ignored

32. Event-listener Interfaces Of Package java.awt.event

33. Textfields JTextField JPasswordField
Single-line area in which user can enter text
JPasswordField
Extends JTextField
Hides characters that user enters
View Figure 11.9, Test Program 11.10
Illustrates capabilities of textfields
Note help on handling number fields

34. How Event Handling Works
You must register the event handler
Through component’s method addActionListener

35. How Event Handling Works
The component knows to call actionPerformed because …
Event is dispatched only to listeners of appropriate type
Each event type has corresponding event-listener interface
Event ID specifies event type that occurred

36. Event Registration for JTextField textField1

37. JButton Button Component user clicks to trigger a specific action
Several different types
Command buttons
Check boxes
Toggle buttons
Radio buttons
javax.swing.AbstractButton subclasses
Command buttons are created with class JButton
Generate ActionEvents when user clicks button

38. Swing Button Hierarchy

39. JButton Example View, ButtonFrame class, Figure 11.15
Test program, Figure 11.16
Look for
Declaration of the buttons
Inner class ButtonHandler which does event handling for the button
Call to .addActionListener(handler) method registers buttons to receive events
The actionPerformed() method

40. Comments on JButton To detect when user clicks button
Program must have an object that implements ActionListener interface
Program must register object as an action listener on the button (the event source)
Using the addActionListener method

41. Comments on JButton JButtons can have a rollover icon
When user clicks the button, it fires an action event.
Results in the invocation of the action listener's actionPerformed method
The only method in the ActionListener interface
JButtons can have a rollover icon
Appears when mouse is positioned over a button
Added to a JButton with method setRolloverIcon

42. Buttons That Maintain State
Swing contains three types of state buttons
JToggleButton, JCheckBox and JRadioButton
JCheckBox and JRadioButton are subclasses of JToggleButton

43. JCheckBox
Contains a check box label that appears to right of check box by default
Generates an ItemEvent when it is clicked
ItemEvents are handled by an ItemListener
Passed to method itemStateChanged
Method isSelected returns whether check box is selected (true) or not (false)
View example class Figure test Figure 11.18
Things to Note:
Declaration of JCheckBox references
Instantiation of JCheckBox objects
Register JCheckBox's to receive events from CheckBoxHandler
CheckBoxHandler invokes method itemStateChanges
Change JTextField font, depending on which JCheckBox was selected

44. JRadioButton Has two states – selected and unselected
Normally appear in a group in which only one radio button can be selected at once
Group maintained by a ButtonGroup object
Declares method add to add a JRadioButton to group
Usually represents mutually exclusive options
View RadioButtonFrame, Figure Test program, Figure 11.20

45. Demonstration of JRadioButton
When viewing Figure 11.19, look for the following
Declaration of JRadioButton references
Group specification
Instantiation of JRadioButton objects
Registration of JRadioButton's to receive events
RadioButtonHandler invokes method itemStateChanged

46. JComboBox JComboBox Note features in Figure 11.21
List of items from which user can select
Also called a drop-down list
Note features in Figure 11.21
Instantiate JComboBox to show three Strings from names array at a time
Register JComboBox to receive events
ItemListener invokes method itemStateChanged

47. JList A list is a series of items JList demonstration, Figure 11.23
User can select one or more items
Single-selection vs. multiple-selection
JList demonstration, Figure 11.23
Note use of ColorNames array to populate JList
Specification of SINGLE_SELECTION
Registration of JList to receive events
ListSelectionListener invokes method valueChanged
Background set according to user choice

48. Multiple-Selection Lists
Multiple-selection list capabilities
Select many items from Jlist
Allows continuous range selection
Look for the following in Figure 11.25
Use of ColorNames array
Specification of MULTIPLE_INTERVAL_SELECTION option
Use of JButton and JListCopyList method

49. Mouse Events Create a MouseEvent object
Handled by MouseListeners and MouseMotionListeners
MouseInputListener combines the two interfaces
Interface MouseWheelListener declares method mouseWheelMoved to handle MouseWheelEvents

50. Mouse Event Handling Event-listener interfaces for mouse events
MouseListener
MouseMotionListener
Listen for MouseEvents
In Figure note use of…
Register JFrame to receive mouse events
Methods invoked for various mouse events
(Note that program does not seem to perform as advertised when run under ReadyTo !!?)

51. Listener Interfaces

52. Listener Interfaces

53. Listener Interfaces
Suppose your class directly implements MouseListener,
Then you must implement all five MouseListener methods.
Even if you care only about mouse clicks
Methods for those events you don't care about can have empty bodies.
Resulting collection of empty method bodies can make code harder to read and maintain

54. Adapter Classes Solution is to use adapter classes
For example, the MouseAdapter class implements the MouseListener interface.
An adapter class implements empty versions of all its interface's methods.

55. Adapter Classes To use an adapter
Create a subclass of it, instead of directly implementing a listener interface.
By extending MouseAdapter, your class inherits empty definitions of all five of the methods that MouseListener contains.

56. Adapter Classes Characteristics of an adapter class
Implements interface
Provides default implementation of each interface method
Used when all methods in interface is not needed

57. Adapter Classes Example of use of an adapter class Note
Figure , the Painter program
Note
Registration of MouseMotionListener to listen for window’s mouse-motion events
Override method mouseDragged, but not method mouseMoved
Store coordinates where mouse was dragged, then repaint JFrame

58. Extending MouseAdapter
The MouseDetails.java program, Note example, Figure 11.31
Demonstrates
How to determine the number of mouse clicks
How to distinguish between different mouse buttons

59. InputEvent Methods Help distinguish among left-, center- and
right-mouse-button clicks

60. Key Event Handling Interface KeyListener Handles key events KeyEvent
Generated when keys on keyboard are pressed and released
KeyEvent
Contains virtual key code that represents key
Demonstrated in Figure 11.36

61. Layout Managers Layout manager capabilities
Provided for arranging GUI components
Provide basic layout capabilities
Processes layout details
Programmer can concentrate on basic “look and feel”
Interface LayoutManager

62. Layout Managers
Layout manager methods

63. FlowLayout Most basic layout manager
GUI components placed in container from left to right
Example program, Figure 11.39
Layout set as FlowLayout
Note results as user presses button

64. BorderLayout Arranges components into five regions
NORTH (top of container)
SOUTH (bottom of container)
EAST (left of container)
WEST (right of container)
CENTER (center of container)
View example, Figure 11.41

65. GridLayout Divides container into grid of specified row an columns
Components are added starting at top-left cell
Proceed left-to-fight until row is full
GridLayout demonstration, Figure 11.43
Clicking buttons toggles between different layouts

66. Panels Helps organize components Class JPanel is JComponent subclass
May have components (and other panels) added to them
Panel example, Figure 11.45

67. Applying Concepts
Suppose you wish to have a GUI which accomplishes the following
Enter numbers in text boxes
Press button to do calculations

68. Step By Step View code to create the window Note
Class (program) extends JFrame
Constructor sets up window using methods inherited from JFrame
Method main()instantiates class object

69. Add the Text Labels View additional code Note
Declaration, instantiation of JLabels
Container reference, pane Gets handle for contentPane
pane layout specified
JLabels added

70. Add the Text Boxes
View next iteration of code for adding the JTextFields
Note
Declaration, instantiation of JTextFields
Change grid layout of pane for 2 columns
Adding to pane

71. Final Version View final code version Note
Declaration, instantiation of buttons
Declaration, definition, instantiation of action handlers
Different author, does not use inner anonymous classes
Add action handlers to the buttons
Our program never actually calls the action handlers

72. Implement an Event Handler
Every event handler requires three bits of code:
Code that specifies that the class either
Implements a listener interface or
Extends a class that implements a listener interface.
For example: public class MyClass implements ActionListener {…
Code that registers an instance of the event handler class as a listener upon one or more components. For example: someComponent.addActionListener(instanceOfMyClass);
Code that implements the methods in the listener interface. For example: public void actionPerformed(ActionEvent e) { ...//code that reacts to the action... }