Graphical User Interface Components: Part 1

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Graphical User Interface Components Part 1

• Chapter 11

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Graphical User Interface (GUI)

• Gives program distinctive ______________
• Provides users with basic level of familiarity
• Built from GUI ________________ (controls,
  widgets, etc.)
• User interacts with GUI component via mouse,
  keyboard, etc
• Check out this visual index of components

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Netscape Window With GUI Components
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Dialog Boxes

• Used by applications to interact with the user
• Provided by Javas JOptionPane class
• Contains input dialogs and message dialogs
• View example program, Figure 11.2

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Dialog Boxes

• Note icon
• Other icons available

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Some Basic GUI Components
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Overview

• Swing GUI components
• Declared in package __________________
• Most are ____________ Java components
• Part of the Java Foundation Classes (JFC)
• Abstract Window Toolkit (AWT)
• ___________________ to Swing
• Declared in package java.awt
• Does not provide consistent, cross-platform
  look-and-feel

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Lightweight vs. Heavyweight

• Lightweight components
• Not tied directly to ________________________
  supported by underlying platform
• Heavyweight components
• Tied directly to the ____________ platform
• AWT components
• Some Swing components

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Superclasses of Swings Lightweight GUI Components

• Class Component
• (package java.awt)
• ______________________ of Object
• Declares many behaviors and attributes common to
  GUI components

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Superclasses of Swings Lightweight GUI Components

• Class Container
• (package java.awt)
• Subclass of Component
• _____________________ Components

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Superclasses of Swings Lightweight GUI Components

• Class JComponent
• (package javax.swing)
• Subclass of Container
• _________________ of all lightweight Swing
  components

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Common Lightweight Component Features

• Pluggable look-and-feel
• _______________ the appearance of components
• Shortcut keys
• mnemonics
• Common ____________________ capabilities
• Brief description of components purpose
• tool tips
• Support for _____________________

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Displaying Text and Images in a Window

• Class JFrame
• Most windows are an instance or subclass of this
  class
• Provides _______________________
• Provides min, max, close ______________
• Label
• ______________________ or information stating the
  purpose of each component
• Created with class JLabel

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Three Parts of a GUI Application

• ________________________ that make up the
  Graphical User Interface
• ________________ that receive the events and
  respond to them
• ____________________ that does useful work for
  the user

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Events Generated by Swing Components
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Events Generated by Swing Components

• Each __________ is represented by an object
• Object gives information about the event
• Identifies the event _________________.
• Event sources are typically _____________,
• Other kinds of objects can also be event sources.
  
• Each event source can have _____________
  listeners registered on it.
• Conversely, a single listener can register with
  multiple event sources.

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JLabel

• Label
• Provide ________________ on GUI
• Defined with class JLabel
• Can display
• Single line of read-only text
• __________________________
• Text and image
• View Figure 11.6
• Note uses of the JLabel Class

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Creating and Attaching label1

• Method setToolTipText of class JComponent
• Specifies the tool tip
• Method add of class Container
• Adds a _________________ to a container

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Creating and Attaching label2

• Interface Icon
• Can be added to a ________________ with the
  setIcon method
• Implemented by class ImageIcon

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Creating and Attaching label2

• Interface SwingConstants
• Declares a set of ________________________________
  ___ such as those used to set the alignment of
  components
• Can be used with methods setHorizontalAlignment
  and setVerticalAlignment

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Creating and Attaching label3

• Other JLabel methods
• getText and ____________________
• For setting and retrieving the text of a label
• getIcon and setIcon
• For setting and retrieving the _______________
  displayed in the label
• getHorizontalTextPosition and setHorizontalTextPos
  ition
• For setting and retrieving the horizontal
  position of the text displayed in the label

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Some basic GUI Components.
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Other JFrame Methods

• setDefaultCloseOperation
• Dictates how the ____________________________
  when the user clicks the close button
• setSize
• Specifies the width and height of the __________
• setVisible
• Determines whether the window is displayed (true)
  or not (false)

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Event Handling

• An event occurs every time the user
• ________________ a character or
• Pushes a _________________________
• Any object can be ________________ of the event.
• That object must
• ________________ the appropriate interface
• Be registered as an event _____________ on the
  appropriate event source.

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Event Handling

• GUI's are _______________ driven
• 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

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Some Event Classes Of Package java.awt.event
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Event Handling Model

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

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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 ______________
• Clicking the mouse on a button
• ______________ some text into a text area
• For a program to respond to an event there must
  be an ____________ object in the GUI program that
  listens to that type of event

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What is an Event Listener?

• An event listener is an _____________
• It "listens" for events from a specific GUI
  component (itself an object)
• When an event is generated by the GUI component
• A ____________ in the listener object is invoked
  to respond to the event

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What If ?

• When there is no event ______________ for an
  event
• A program can ____________ events
• If there is no listener for an event, the event
  is just ignored

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

• JTextField
• __________ area in which user can enter text
• JPasswordField
• Extends JTextField
• ______________ characters that user enters
• View Figure 11.9
• Illustrates capabilities of textfields
• Note help on handling number fields

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How Event Handling Works

• You must ______________ the event handler
• Through components method addActionListener

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How Event Handling Works

• The component knows to call actionPerformed
  because
• Event is _______________ only to listeners of
  appropriate type
• Each event type has corresponding event-listener
  interface
• Event _____________ specifies event type that
  occurred

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Event Registration for JTextField textField1
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JButton

• Button
• Component user clicks to trigger a specific
  action
• Several different types
• Command ________________
• Check ________________
• Toggle buttons
• __________________ buttons
• javax.swing.AbstractButton subclasses
• Command buttons are created with class JButton
• Generate __________________________ when user
  clicks button

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Swing Button Hierarchy
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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

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Comments on JButton

• To detect when user clicks button
• Program must have an _______________ that
  implements ActionListener interface
• Program must __________ object as an action
  listener on the button (the event source)
• Using the addActionListener method

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Comments on JButton

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

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Buttons That Maintain State

• Swing contains three types of ____________
  buttons
• JToggleButton, JCheckBox and JRadioButton
• JCheckBox and JRadioButton are ______________ of
  JToggleButton

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JCheckBox

• Contains a check box ______________ that appears
  to right of check box by default
• Generates an ItemEvent when it is ____________
• ItemEvents are handled by an ItemListener
• Passed to method _______________________
• Method isSelected returns whether check box is
  selected (true) or not (false)
• View example class Figure 11.17test Figure 11.18

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JRadioButton

• Has two states selected and unselected
• Normally appear in a _____________ 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 ____________ options
• View RadioButtonFrame, Figure 11.19Test program,
  Figure 11.20

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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

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JComboBox

• JComboBox
• 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

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JList

• A list is a series of items
• User can _____________ 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 __________ events
• ListSelectionListener invokes method valueChanged
  
• Background set according to user choice

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Multiple-Selection Lists

• Multiple-selection list capabilities
• Select ______________ items from Jlist
• Allows continuous _________ 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

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Mouse Events

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

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Mouse Event Handling

• Event-listener interfaces for mouse events
• MouseListener
• MouseMotionListener
• Listen for MouseEvents
• In Figure 11.28 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 !!?)

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Listener Interfaces
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Listener Interfaces
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Listener Interfaces

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

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Adapter Classes

• Solution is to use __________________ classes
• For example, the MouseAdapter class implements
  the MouseListener interface.
• An adapter class implements ____________ of all
  its interface's methods.

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Adapter Classes

• To use an adapter
• Create a ________________ of it, instead of
  directly implementing a listener interface.
• By extending MouseAdapter, your class
  _________________ empty definitions of all five
  of the methods that MouseListener contains.

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Adapter Classes

• Characteristics of an adapter class
• _________________ interface
• Provides ________________ implementation of each
  interface method
• Used when all methods in interface is not needed

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Adapter Classes

• Example of use of an adapter class
• Figure 11.34 , the Painter program
• Note
• Registration of MouseMotionListener to listen for
  windows __________________ events
• ____________________ method mouseDragged, but not
  method mouseMoved
• Store ________________ where mouse was dragged,
  then repaint JFrame

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Extending MouseAdapter

• The MouseDetails.java program, Note example,
  Figure 11.31
• Demonstrates
• How to determine the __________ of mouse clicks
• How to distinguish between _______________ mouse
  buttons

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InputEvent Methods

• Help distinguish among
• left-,
• center- and
• right-mouse-button clicks

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Key Event Handling

• Interface KeyListener
• Handles key events
• Generated when keys on keyboard are pressed and
  released
• KeyEvent
• Contains ___________________ that represents key
• Demonstrated in Figure 11.36

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Layout Managers

• Layout manager capabilities
• Provided for _________________ GUI components
• Provide basic layout capabilities
• Processes layout details
• Programmer can concentrate on basic look and
  feel
• Interface LayoutManager

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Layout Managers

• Layout manager methods

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FlowLayout

• _____________________ layout manager
• GUI components placed in container from _________
  to ______________
• Example program, Figure 11.39
• Layout set as FlowLayout
• Note results as user presses button

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BorderLayout

• Arranges components into five ___________
• 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

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GridLayout

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

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Panels

• Helps organize components
• Class JPanel is ____________ subclass
• May have components (and other _____________)
  added to them
• Panel example, Figure 11.45

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Applying Concepts

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

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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

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Add the Text Labels

• View additional code
• Note
• Declaration, instantiation of JLabels
• Container reference, paneGets handle for
  contentPane
• pane layout specified
• JLabels added

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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

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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

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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.addActionL
  istener(instanceOfMyClass)
• Code that implements the methods in the listener
  interface. For example public void
  actionPerformed(ActionEvent e) ...//code that
  reacts to the action...