Go Over Test

1
Go Over Test 2

• Grade Breakdown Fall 2005
• A's 3
• B's 3
• C's 2
• D's 2
• How to Study for CSc-037
• Visit the instructor's office for help
• Work on HW Early (as opposed to starting it the
  night before it is due)
• Read Text Before After Class
• Make sure you understand what's happening in Lab
• Play with Sample Programs in Course Folder
• Work on Exercises in Textbook
• Try Sample Tests without looking at answers
• (not just the night before the test)

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Week 08 - a

• Swing GUIJTextField, JTextArea, JButtonJLabel,
  JPanel, JFrame
• EventsActionListener InterfaceMouseListener,
  MouseMotionListener

3
Sample Programs Referenced(code located in
course folder)

• GUI Hello
• Temperature Convert

• Turtle Graphics
• Measles (ClickMe)
• TicTacToe
• Sleepy Eyes
• java events.EventLab

4
AWT and Swing

• GUI Graphical User Interface
• Windows, buttons, text boxes, etc.
• AWT Abstract Window Toolkit
• Early set of classes for building GUIs
• Platform dependent
• Swing
• More recent set of classes for building GUIs
• Platform independent
• Relies on AWT

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Categories of Classes

• Components
• like frames, panels, buttons, text boxes,
• Layout management
• Control flow of components
• Help position components
• Events
• Generated when users click buttons, move the
  mouse,
• Listeners
• Methods activated by operating system when events
  occur

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Creating a GUIHello

• Start with a class that IS A JFrame
• public class HelloGUI extends JFrame
• Set its size, title, and other properties
• setSize(width, height)
• setTitle(text)
• setResizeable(false) // optional
• Set what it should do when the user closes it
• setDefaultCloseOperation( EXIT_ON_CLOSE)
• (Precludes need for WindowListener)
• Needed in JFrame, not Applet
• Write an application class that instantiates the
  GUI and makes it visible
• theGUI.setVisible(true)

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Example Problem
175 pixels
375 pixels
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Frames

• A frame is a window with a title bar and a border
• The Frame class is a subclass of Container class
• Container class objects may have other components
  (e.g. Buttons or Labels) added to them using the
  add method
• A typical Java GUI will create and display one or
  more frames
• To make a frame visible the message
  setVisible(true) must be sent to the frame

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JFrame and Content Pane
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Create the JFrame

• The HelloGUI class
• Extends JFrame
• Constructor that
• Sets the size to 375 by 175
• Sets the title to Hello
• Makes the frame not resizable
• Sets the close operation
• Application class that
• Instantiates a HelloGUI object
• Makes the GUI visible

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Add Instructions

• Need Container object to hold the content pane
• Set its background color to white
• Set the layout to null (more on layouts later)
• Need a JLabel object for the instructions
• Set the bounds
• Position at (125, 10)
• Dimensions 250 by 25
• Add the JLabel object to the content pane

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Add Text Boxes and Buttons

• Make instance variables for the two text boxes
  and buttons
• JTextField and JButton
• Instantiate in GUI constructor
• Set bounds
• Name (125, 40, 200, 25)
• Message (125, 100, 200, 25)
• Enter (125, 70, 125, 25)
• Clear (250, 70, 75, 25)
• Add text boxes and buttons to content pane

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Java Event Model

• An event model describes how events are handled
  in the language
• Java uses event generators and event listeners
• An event generator initiates an event of a
  particular type
• e.g. clicking a button generates an action event
• A event listener listens for and responds to
  events of a particular type
• e.g. our GUI will listen for action events and
  have a method that will say what to do in
  response to an action event
• Also, the java.awt.event package must be imported

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Registering as anEvent Listener

• The GUI needs to tell the event generator that it
  is a listener
• This is called registering
• An event listener registers itself with an event
  generator
• e.g. enter.addActionListener(this)
• enter is the event generator
• this (the GUI) is the listener
• In order to for an object to be a listener it
  must follow protocols
• It must have an actionPerformed event
• The protocols are defined in the ActionListener
  interface
• The listener class must implement ActionListener

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The actionPerformed Method

• Specified in the ActionListener interface
• public void actionPerformed(ActionEvent e)
• Does the task(s) that should be performed when
  the action occurs
• E.g. Writes the message in the text box
• Not explicitly called
• Automatically called when an event occurs for
  which there is a registered listener
• The parameter gives the action object that is
  being processed
• That way we can tell which button was pressed

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Working with Images

• An object of the JLabel class can hold text or an
  ImageIcon object
• An ImageIcon object holds an image
• new ImageIcon( filename of image )
• Modify the GUI
• Add another JLabel object as an instance variable
• Instantiate it with a constructor that takes an
  ImageIcon object as its argument
• e.g. image new JLabel(new ImageIcon(RedFace.gif
  )
• Set its bounds to (15, 20, 90, 99)
• Add it to the content pane
• Move the image RedFace and BlueFace into the
  project folder

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Changing the Images

• Modify the actionPerformed method to change the
  image
• Set the image to the red face when the enter
  button is pressed
• Set the image to the blue face when the clear
  button is pressed.
• Use setIcon method of the JLabel
• e.g. Image.setIcon(new ImageIcon(BlueFace.gif)

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Display the MessageHello

• Modify the GUI to implement ActionListener
• Register the GUI as a listener for both buttons
• enter.addActionListener(this)
• clear.addActionListener(this)
• Write an actionPerformed method to set the text
  in message to the String "Hello, " plus the text
  in name.
• Use the setText and getText methods of the
  JTextFields
• Try it
• Try the enter button
• Try the clear button
• How do we make them do different things?

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Sensing the Object

• Need to know who initiated the event
• The ActionEvent object that is the methods
  parameter holds the information
• Its getSource() method can be called to get a
  reference to the object
• e.g. e.getSource() would return a reference to
  either the enter or clear button object
• We can test it and use a decision structure to
  decide what to do
• Add
• Object buttonPressed e.getSource()
• The decision structure

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Entering Text can alsoTrigger an actionEvent

• Add the actionListener to the text field
• May need to determine which text field caused the
  event
• See Temperature Project in BlueJ
• (also listed on next 3 slides)
• Watch what happens if we resize the window
• Flow Layout
• Don't need to specify the location of each object

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Temperature Conversion(1 of 3)

• import java.awt.
• import java.awt.event.
• import javax.swing.
• /
• GUI to convert between Fahrenheit and
  Centigrade Temperatures.
• _at_author Dave Hannay
• _at_version 21 February 2004
• /
• public class Temperature extends JFrame
  implements ActionListener
• JTextField txtFahr new JTextField(6),
• txtCent new JTextField(6)

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Temperature Conversion(2 of 3)

• public Temperature()
• this.setSize(250,100)
• this.setTitle("Temperature Conversion")
• this.setDefaultCloseOperation(EXIT_ON_CLOSE)
• Container frame this.getContentPane()
• frame.setLayout(new FlowLayout())
• Panel fahrPanel new Panel()
• Panel centPanel new Panel()
• fahrPanel.add(new JLabel("Fahrenheit"))
  fahrPanel.add(txtFahr)
• centPanel.add(new JLabel("Centigrade"))
  centPanel.add(txtCent)
• frame.add(fahrPanel)
• frame.add(centPanel)
• txtFahr.addActionListener(this)
• txtCent.addActionListener(this)
• // end of Temperature constructor

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Temperature Conversion(3 of 3)

• public void actionPerformed(ActionEvent e)
• double fahr, cent
• // check for user input in txtFahr TextField
• if (e.getSource() txtFahr)
• fahr Double.parseDouble(txtFahr.getText())
  
• cent 5.0 (fahr - 32.0) / 9.0
• txtCent.setText(""cent) // the old
  convert to String trick
• // end of fahrenheit to centigrade
• else
• cent Double.parseDouble(txtCent.getText())
  
• fahr 9.0 cent / 5.0 32.0
• txtFahr.setText(""fahr)
• // end of centigrade to fahrenheit
• // end of actionPerformed method
• // end of Temperature class

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HW 7(see Sample HW 7)

• GUI Interface for CD Collection
• See Textbook, problem 4, page 514
• Store info on your CD Collection in an array (or
  Vector if you prefer) of Objects of type CD
• Do not use Text Files for this assignment
• i.e. do not look ahead to chapter 8
• It will tend to make things more confusing

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Java BREAK
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Turtle Graphics

• Moves around screen based on button clicks
• Vector to remember where it has been
• so it can draw trailing line
• See in BlueJ

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Mouse Interfaces

• Java AWT provides a several interfaces for
  handling mouse events
• MouseListener
• has abstract methods mouseClicked, mousePressed,
  mouseReleased, mouseEntered, mouseExited
• MouseMotionListener
• has abstract methods mouseMoved, mouseDragged
• If a class should recognize mouse events, the
  class must implement one or both of the
  interfaces
• The class must then contain concrete definitions
  of ALL of the methods in the interface(s)
• if a method is not used, its body may be empty

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Creating "Mouse Click" Listeners

• Import the java.awt.event package
• In the class header, add the words implements
  MouseListener
• Send the addMouseListerner(this) message to the
  mouse event manager (should be done in the
  constructor method)
• Define methods mouseClicked, mousePressed,
  mouseReleased, mouseEntered, mouseExited

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Mouse Listener Template

• import java.awt.event.
• public class classname implements MouseListener
• // include manager.addMouseListener(this)
• // manager is a an applet for now, so omitted
• // in some initialization method
• public void mouseClicked (MouseEvent e)
• public void mousePressed (MouseEvent e)
• public void mouseReleased (MouseEvent e)
• public void mouseEntereded (MouseEvent e)
  
• public void mouseExited (MouseEvent e)

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Finding Mouse Location

• Inside mouseClicked, the argument e of type
  MouseEvent can be used to find the location of
  the mouse cursor
• The call e.getX( ) returns the value of the
  horizontal coordinate of the mouse cursor
  position
• The call e.getY( ) returns the value of the
  vertical coordinate of the mouse cursor position

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MouseListener ExampleMeasles (ClickMe)

• import java.awt.event.
• implements MouseListener clause in method header
• addMouseListener(this) in init method
• Every MouseListener method must be implemented,
  even if empty
• 5 of them
• Use of getX(), getY()

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ClickMe ClassRun in BlueJ

• import java.awt.
• import java.applet.
• import java.awt.event.
• import java.util.
• // David Hannay 21 February 2004
• public class ClickMe extends Applet implements
  MouseListener
• private int radius 7
• private Color color Color.RED
• private Vector spots
• public void init()
• spots new Vector()
• addMouseListener(this)
• // end of init method
• public void paint(Graphics g)
• for (int s0 sltspots.size() s)
• int x ((Point) spots.get(s)).x
• int y ((Point) spots.get(s)).y
• g.setColor(color)

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ClickMeHandling Mouse Actions

• public void mouseClicked(MouseEvent event)
• spots.addElement(new Point(event.getX(),
  event.getY()))
• repaint()
• // end of mouseClicked method
• public void mousePressed(MouseEvent event)
• public void mouseReleased(MouseEvent event)
  
• public void mouseExited(MouseEvent event)
• color Color.GREEN
• repaint()
• // end of mouseExited method
• public void mouseEntered(MouseEvent event)
• color Color.RED
• repaint()
• // end of mouseEntered method
• // end of ClickMe class

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TicTacToe

• A more "practical" use of MouseListener
• Run Program in BlueJ, then take a look at the
  TicTacToe class

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TTTBoard Class (1 of 2)

• public class TTTBoard
• public static int EX 0, OH 1, VACANT 2
• private int sq VACANT, VACANT, VACANT,
• VACANT, VACANT, VACANT,
• VACANT, VACANT,
  VACANT
• public boolean isMarked (int row, int col)
• return sqrow-1col-1 ! VACANT
• // end of isMarked method
• public int getMark (int row, int col)
• return sqrow-1col-1
• // end of getMark method
• public void putO (int row, int col)
• sqrow-1col-1 OH
• // end of putO method
• public void putX (int row, int col)

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TTTBoard Class (2 of 2)

• public boolean done ()
• for (int i0 ilt3 i)
• for (int j0 jlt3 j)
• if (sqijVACANT) return false
• return true
• // end of done method
• public int winner ()
• int center, ul, lr
• center sq11
• if ((center sq00 center
  sq22)
• (center sq02 center
  sq20)
• (center sq01 center
  sq21)
• (center sq10 center
  sq12)) return center
• ul sq00
• if ((ul sq01 ul sq02)
• (ul sq10 ul sq20))
  return ul
• lr sq22
• if ((lr sq12 lr sq02)

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Creating Mouse Motion Listeners

• Import the java.awt.event package
• In the class header, add the words implements
  MouseMotionListener
• Send the message addMouseMotionListener(this) to
  the mouse event manager (should be done in the
  constructor method)
• Define methods mouseMoved (mouse up) and
  mouseDragged (mouse down)

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Mouse Motion Listener Template

• import java.awt.event.
• public class classname implements
  MouseMotionListener
• // include manager.addMouseListener(this)
• // (manager. not needed for applets)
• // in some initialization method
• public void mouseMoved (MouseEvent e)
• public void mouseDragged (MouseEvent e)

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Mouse Motion

• mouseMoved will be called each time the mouse
  makes a significantly large movement
• mouseDragged will be called instead if the mouse
  button is pressed and the mouse makes a
  significantly large movement

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Listening to All Mouse Events

• To catch all seven mouse events use the following
  class header
• public class classname implements MouseListener,
  MouseMotionListener
• You then need to define all seven mouse methods
  mouseMoved, mouseDragged, mouseClicked,
  mousePressed, mouseReleased, mouseEntered,
  mouseExited

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SleepyEyes

• See in BlueJ
• implements MouseListener and MouseMotionListener
• several concrete methods are implemented
• others are empty
• do nothing

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EventLab(AnimatedIllustrations)

• Everyone grab a PC and double-click MS-DOS prompt
  icon
• "Volunteer" to run it on instructor's console
• java events.EventLab

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Java BREAK