Graphical%20User%20Interfaces

1
Graphical User Interfaces

• Javas AWT and Swing APIs

2
AWT and Swing

• Java provides two sets of components for GUI
  programming
• AWT classes in the java.awt package
• Swing classes in the javax.swing package

3
Abstract Window Toolkit (AWT)

• The Abstract Window Toolkit is a portable GUI
  library.
• AWT provides the connection between your
  application and the native GUI.
• AWT provides a high-level abstraction since it
  hides you from the underlying details of the GUI
  your program will be running on.
• AWT components depend on native code counterparts
  (called peers) to handle their functionality.
  Thus, these components are often called
  heavyweight components.

4
Swing

• Swing implements GUI components that build on AWT
  technology.
• Swing is implemented entirely in Java.
• Swing components do not depend on peers to handle
  their functionality. Thus, these components are
  often called lightweight components.

5
Swing Stack
6
AWT Pros and Cons

• Pros
• Speed native components speed performance.
• Look and feel AWT components more closely
  reflect the look and feel of the OS they run on.
• Cons
• Portability use of native peers creates
  platform specific limitations.
• Features AWT supports only the lowest common
  denominatore.g. no tool tips or icons.

7
Swing Pros and Cons

• Pros
• Portability Pure Java implementation.
• Features Not limited by native components.
• Look and Feel Pluggable look and feel.
  Components automatically have the look and feel
  of the OS their running on.
• Cons
• Performance Swing components handle their own
  painting (instead of using APIs like DirectX on
  Windows).
• Look and Feel May look slightly different than
  native components.

8
Summary of AWT vs. Swing

• Use Swing!

9
Model-view-controller (MVC)

• Classic MVC architecture divides each component
  into three parts a model, a view, and a
  controller.
• The model manages whatever data or values the
  component uses, such as a combo boxs list
  elements.
• The view manages the way the component is
  displayed.
• The controller determines what happens when the
  user interacts with the componentfor example,
  what occurs when the user clicks a button control.

10
Swings Modified MVC Design

• In Swing's separable model design, the model part
  of a component is treated as a separate element,
  just as the MVC design does.
• But Swing collapses the view and controller parts
  of each component into a single user interface
  object.

11
Swing Classes

• Swing classes are located in the javax.swing
  package.
• Swing classes generally start with the letter J.
• For example, a GUI button in AWT is the Button
  class. In Swing, its called JButton.

12
Hello World Example

• import javax.swing.
• public class HelloWorldSwing
• public static void main(String args)
• JFrame frame new JFrame("HelloWorldSwing")
• final JLabel label new JLabel("Hello World")
• frame.getContentPane().add(label)
• frame.setDefaultCloseOperation( JFrame.EXIT_ON
  _CLOSE)
• frame.pack()
• frame.setVisible(true)

13
Top-level Containers

• There are three top-level Swing containers
• JFrame window that has decorations, such as a
  border, a title, and buttons for iconifying and
  closing the window
• JDialog a window that's dependent on another
  window
• JApplet applet's display area within a browser
  window

14
Containment Hierarchy

• In the Hello World example, there was a content
  pane.
• Every top-level container indirectly contains an
  intermediate container known as a content pane.
• As a rule, the content pane contains, directly or
  indirectly, all of the visible components in the
  window's GUI.
• To add a component to a container, you use one of
  the various forms of the add method.

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Containment Hierarchy of the Hello World Example
JFrame

content pane
JLabel
16
And now, a quick diversion

• Inner classes and anonymous inner classes are
  very important in GUI programming.
• Lets talk about them before presenting the next
  GUI example.

17
Nested and Inner Classes

• Nested class static class defined inside
  another class it forms a relationship between
  classes
• Inner class non-static class defined inside
  another class it forms a relationship between
  objects

18
Inner Classes

• Inner class instances can only exist inside
  enclosing objects.
• Inner class instances have access to all
  (including private) members of the enclosing
  class.
• Use inner classes when a class only makes sense
  in the context of the enclosing class or when it
  relies on its enclosing class for its function.

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Inner Class Diagram
instance of enclosing class
instance of inner class
20
Inner Class Example

• public class Stack
• private Vector items
• ...
• public Iterator iterator()
• return new StackIter()
• class StackIter implements Iterator
• int currentItem items.size() - 1
• public boolean hasNext()
• return (currentItem gt 0)
• public Object next()
• if (!hasNext())
• throw new NoSuchElementException()
• else return items.elementAt( currentItem--)
  
• // end inner class StackIter
• // end class Stack

21
Example Summary

• Lets analyze the previous example by asking
  about other ways to accomplish the same thing
• Make StackIter a regular class Then we have to
  associate a StackIter instance with a Stack
  instance. If StackIter is an inner class, it is
  already associated!
• Make Stack implement Iterator Then only one
  thread can iterate the stack object at a time!
• So inner classes can provide elegant solutions to
  otherwise difficult problems.

22
Anonymous Inner Classes

• You can create an inner class without giving it a
  name.
• Anonymous classes can make code hard to read.
  They should be used for short classes (one method
  or two).
• Anonymous classes are commonly used as event
  handling classes.

23
Anonymous Class Example

• public class Stack
• private Vector items
• ...
• public Iterator iterator()
• return new Iterator()
• int currentItem items.size() - 1
• public boolean hasNext()
• return (currentItem gt 0)
• public Object next ()
• if (!hasNext()) throw new NoSuchElementEx
  ception()
• else return items.elementAt( currentI
  tem--)
• // end anonymous class
• // end class Stack

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Event Example (using anonymous inner class)

• public class SwingApplication extends JFrame
• private static String labelPrefix "Number of
  button clicks "
• private int numClicks 0
• JLabel label new JLabel(labelPrefix "0
  ")
• public SwingApplication(String title)
• super(title)
• JButton button new JButton("I'm a Swing
  button!")
• button.addActionListener(new ActionListener()
  
• public void actionPerformed(ActionEvent e)
  
• label.setText(labelPrefix numClicks)
• )
• JPanel panel new JPanel()
• panel.add(button)
• panel.add(label)
• getContentPane().add(panel)
• pack()
• setVisible(true)

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Example Summary

• Anonymous inner classes make the code clearer by
  keeping the implementation of an event handler
  close to where the event handler is registered.

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Handling Events

• Every time the user types a character or pushes a
  mouse button, an event occurs.
• Any object can be notified of the event.
• All the object has to do is implement the
  appropriate interface and be registered as an
  event listener on the appropriate event source.

27
How to Implement an Event Handler

• Every event handler requires three pieces of
  code
• declaration of the event handler class that
  implements a listener interface or extends a
  class that implements a listener interface
• public class MyClass implements ActionListener
• registration of an instance of the event handler
  class as a listener
• someComponent.addActionListener(instanceOfMyClass
  )
• 3. providing code that implements the methods in
  the listener interface in the event handler class
• public void actionPerformed(ActionEvent e)
  ...//code that reacts to the action...

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A Simpler Event Example
1

• public class ButtonClickExample extends JFrame
  implements ActionListener
• JButton b new JButton("Click me!")
• public ButtonClickExample()
• b.addActionListener(this)
• getContentPane().add(b)
• pack()
• setVisible(true)
• public void actionPerformed(ActionEvent e)
• b.setBackground(Color.CYAN)
• public static void main(String args)
• new ButtonClickExample()

2
3
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Example Summary

• (1) declares a class that implements a listener
  interface (i.e. ActionListener)
• (2) registers an instance of this class with the
  event source
• (3) defines the action to take when the event
  occurs

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Threads

• Why does the example continue to run even when
  the main method is done?
• The Java virtual machine terminates all its
  activity and exits when one of two things
  happens
• All the threads that are not daemon threads
  terminate.
• Some thread invokes the exit method of class
  Runtime or class System, and the exit operation
  is permitted by the security manager.
• If were still running after completing the main
  method, there must be other nondaemon threads
  alive.
• There is at least one thread still alive the
  event dispatch thread!
• Note The Java virtual machine initially starts
  up with a single nondaemon thread, which
  typically calls the method main of some class.

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Event Dispatch Thread

• The event dispatch thread is the thread in which
  your listener code executes.
• This thread is a loop that checks the system
  event queue for mouse clicks, key presses, etc.
• The thread grabs an event off the queue and
  determines what to do with it.

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Event Dispatch Thread

• Example
• If the event is a mouse click, then the thread
  checks to see if there is a component where the
  user clicked.
• If there is a component, the thread calls the
  mouse click processing handler for that
  component.
• That component, in turn, could fire other events.
• For example, clicking a JButton means that the
  event thread passes the button click to the
  JButton object which in turn fires its own
  actionPerformed event.
• Any object listening will have their
  actionPerformed method called.

33
Frozen GUIs

• We now know that event handling code executes in
  an single thread, the event dispatching thread.
• This ensures that each event handler finishes
  execution before the next one executes.
• Painting code also executes in the event
  dispatching thread.
• Therefore, while an event handler method is
  executing, the program's GUI is frozenit won't
  repaint or respond to mouse clicks.
• Your event handling code should be quick (or
  alternatively create a new thread) in order to
  keep your GUI responsive.

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Frozen GUI Example

• public class FrozenGUI extends JFrame implements
  ActionListener
• JButton b new JButton("Click me!")
• final long DELAY 5000 // in milliseconds
• public FrozenGUI()
• super("Frozen GUI") // call
  superclass constructor with window title
• setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)
  
• b.addActionListener(this) // register the
  listener
• getContentPane().add(b) // add button to
  frame
• pack() // pack the
  contents
• setVisible(true) // show the
  window
• public void actionPerformed(ActionEvent e)
• long timeToStop System.currentTimeMillis()
  DELAY
• while (System.currentTimeMillis() lt
  timeToStop)
• public static void main(String args)

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Example Summary

• When button is clicked, event handler just spins
  for 5 seconds.
• No painting can occur at this time.
• Notice button still looks pressed even after
  youve let go. Thats because it cant repaint
  itself to look unpressed!

After button click for 5 seconds
Before button click
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Events and Event Listeners
37
ImageIcon

• Some Swing components can be decorated with an
  icona fixed-size image.
• A Swing icon is an object that adheres to the
  Icon interface.
• Swing provides a particularly useful
  implementation of the Icon interface ImageIcon.
• ImageIcon paints an icon from a GIF or a JPEG
  image.

38
ImageIcon Example

• import javax.swing.
• public class ImageIconExample extends JFrame
• public static void main(String args)
• JFrame frame new JFrame("ImageIcon
  Example")
• ImageIcon icon new ImageIcon("smallfrog.jpg"
  )
• JPanel panel new JPanel()
• JButton button new JButton(icon)
• panel.add(button)
• frame.getContentPane().add(panel)
• frame.pack()
• frame.setVisible(true)

39
JTextField Example (1)

• public class CelsiusConverter implements
  ActionListener
• JFrame converterFrame
• JPanel converterPanel
• JTextField tempCelsius
• JLabel celsiusLabel, fahrenheitLabel
• JButton convertTemp
• public CelsiusConverter()
• converterFrame new JFrame("Convert Celsius
  to
• Fahrenheit")
• converterPanel new JPanel()
• converterPanel.setLayout(new GridLayout(2,
  2))
• addWidgets()
• converterFrame.getContentPane().add(converterP
  anel,
• BorderLayout.CENTER)
• converterFrame.setDefaultCloseOperation(
• JFrame.EXIT_ON_CLOSE)
• converterFrame.pack()
• converterFrame.setVisible(true)

40
JTextField Example (2)

• private void addWidgets()
• tempCelsius new JTextField(2)
• celsiusLabel new JLabel("Celsius",
• SwingConstants.LEFT)
• convertTemp new JButton("Convert...")
• fahrenheitLabel new JLabel("Fahrenheit",
• SwingConstants.LEFT)
• convertTemp.addActionListener(this)
• converterPanel.add(tempCelsius)
• converterPanel.add(celsiusLabel)
• converterPanel.add(convertTemp)
• converterPanel.add(fahrenheitLabel)

41
JTextField Example (3)

• public void actionPerformed(ActionEvent event)
  
• int tempFahr (int)((Double.parseDouble(
• tempCelsius.getText())) 1.8 32)
• fahrenheitLabel.setText(tempFahr "
  Fahrenheit")
• public static void main(String args)
• try
• UIManager.setLookAndFeel(
• UIManager.getCrossPlatformLookAndFeelClass
  Name())
• catch(Exception e)
• CelsiusConverter converter new
  CelsiusConverter()
• // end CelciusConverter class

42
JCheckBox Example (1)

• public class CheckBoxDemo extends JPanel
  implements ActionListener
• JCheckBox chinButton
• JCheckBox glassesButton
• JCheckBox hairButton
• JCheckBox teethButton
• JButton goButton new JButton("Go!")
• public CheckBoxDemo()
• chinButton new JCheckBox("Chin")
• chinButton.setSelected(true)
• glassesButton new JCheckBox("Glasses")
• glassesButton.setSelected(true)
• hairButton new JCheckBox("Hair")
• hairButton.setSelected(true)
• teethButton new JCheckBox("Teeth")
• teethButton.setSelected(true)
• goButton.addActionListener(this)
• setLayout(new GridLayout(0, 1))
• add(chinButton)

43
JCheckBox Example (2)

• public static void main(String s)
• JFrame frame new JFrame("CheckBoxDemo")
• frame.setDefaultCloseOperation(
• JFrame.EXIT_ON_CLOSE )
• frame.getContentPane().add(new
  CheckBoxDemo())
• frame.pack()
• frame.setVisible(true)
• public void actionPerformed(ActionEvent e)
• if (glassesButton.isSelected())
• System.out.println("Glasses true")
• else
• System.out.println("Glasses false")
• System.exit(0)

44
Example Summary

• You may not want to be alerted every time the
  user selects or deselects a checkbox.
• A more common use is to check the state of the
  button when the user clicks a button signifying
  that he/she is done and ready to advance.

45
JRadioButton Example (1)

• public class RadioButtonDemo extends JPanel
  implements ActionListener
• String birdString "Bird"
• String catString "Cat"
• String dogString "Dog"
• String rabbitString "Rabbit"
• String pigString "Pig"
• JRadioButton birdButton new
  JRadioButton(birdString)
• JRadioButton catButton new JRadioButton(catStr
  ing)
• JRadioButton dogButton new JRadioButton(dogStr
  ing)
• JRadioButton rabbitButton new
  JRadioButton(rabbitString)
• JRadioButton pigButton new JRadioButton(pigStr
  ing)
• JButton goButton new JButton("Go!")
• public RadioButtonDemo()
• birdButton.setSelected(true)
• ButtonGroup group new ButtonGroup()
• group.add(birdButton)
• group.add(catButton)
• group.add(dogButton)

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JRadioButton Example (2)

• goButton.addActionListener(this)
• setLayout(new GridLayout(0, 1))
• add(birdButton)
• add(catButton)
• add(dogButton)
• add(rabbitButton)
• add(pigButton)
• add(goButton)
• public static void main(String s)
• JFrame frame new JFrame("RadioButtonDemo")
• frame.setDefaultCloseOperation(
• JFrame.EXIT_ON_CLOSE)
• frame.getContentPane().add(new
  RadioButtonDemo(), BorderLayout.CENTER)
• frame.pack()
• frame.setVisible(true)

47
JRadioButton Example (3)

• public void actionPerformed(ActionEvent e)
• if (birdButton.isSelected())
• System.out.println("User finally selected
  bird.")
• System.exit(0)
• if (catButton.isSelected())
• System.out.println("User finally selected
  cat.")
• System.exit(0)
• if (dogButton.isSelected())
• System.out.println("User finally selected
  dog.")
• System.exit(0)
• if (rabbitButton.isSelected())
• System.out.println("User finally selected
  rabbit.")
• System.exit(0)
• if (pigButton.isSelected())

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Example Summary

• ButtonGroup ensures that only one radio button in
  the group can be selected at a time.
• setSelected sets initial state. (Good for
  defaults).
• isSelected checks the state of the button.

49
JComboBox

• A combo box is a button that when pressed,
  presents a list of items that can be selected.

50
JComboBox Example

• public class ComboBoxExample implements
  ActionListener
• JComboBox box
• public ComboBoxExample()
• JFrame frame new JFrame("ComboBoxExample")
• JPanel panel new JPanel()
• Set s new TreeSet()
• s.add(new Integer(1))
• s.add(new Integer(2))
• s.add(new Integer(3))
• box new JComboBox(s.toArray())
• box.addActionListener(this)
• panel.add(box)
• frame.getContentPane().add(panel)
• frame.pack()
• frame.setVisible(true)
• public static void main(String args)
• new ComboBoxExample()

notice use of collection
51
Example Summary

• Notice the use of the Set.
• If we were to get the combo box choices from a
  file, we could prohibit duplicates by using a Set.

52
Dialogs - JOptionPane

• Dialogs are windows that are more limited than
  frames.
• Every dialog is dependent on a frame. When that
  frame is destroyed, so are its dependent dialogs.
  When the frame is iconified, its dependent
  dialogs disappear from the screen. When the
  frame is deiconified, its dependent dialogs
  return to the screen.
• To create simple dialogs, use the JOptionPane
  class.
• The dialogs that JOptionPane provides are modal.
• When a modal dialog is visible, it blocks user
  input to all other windows in the program.

53
JOptionPane Examples

• // show an error dialog
• JOptionPane.showMessageDialog(null, "alert",
  "alert",
• JOptionPane.ERROR_MESSAGE)

54
JOptionPane Examples

• // show Yes/No dialog
• int x JOptionPane.showConfirmDialog(null,
• "choose one", "choose one", JOptionPane.YES_NO_OP
  TION)
• System.out.println("User clicked button " x)

55
JOptionPane Examples

• // show input dialog
• String inputValue JOptionPane.showInputDialog("P
  lease input
• a value")
• System.out.println("User entered "
  inputValue)

56
Layout Management

• Layout managers control the size and arrangement
  of components in a container.
• There are 6 common layout managers
• BorderLayout (demod)
• BoxLayout
• FlowLayout (demod)
• GridBagLayout
• GridLayout (demod)
• CardLayout (demod)

57
Layout Management
58
FlowLayout

• Components are placed in a row from left to right
  in the order in which they are added.
• A new row is started when no more components can
  fit in the current row.
• The components are centered in each row by
  default.
• The programmer can specify the size of both the
  vertical and horizontal gaps between the
  components.
• FlowLayout is the default layout for JPanels.

59
FlowLayoutExample

• public class FlowLayoutTest extends JFrame
• JButton b1new JButton("Red"),
• b2new JButton("Green"),b3new JButton("Blue"),
• b4new JButton("Yellow"),b5newJButton("Pink")
• public FlowLayoutTest()
• setTitle("FlowLayout Test")
• Container pane getContentPane()
• pane.setLayout(new FlowLayout())
• setBounds(0,0,400,100)
• pane.add(b1) pane.add(b2) pane.add(b3)
• pane.add(b4) pane.add(b5)
• public static void main(String args)
• JFrame f new FlowLayoutTest()
• f.setVisible(true)

60
BorderLayout

• Defines five locations where a component or
  components can be added
• North, South, East, West, and Center
• The programmer specifies the area in which a
  component should appear.
• The relative dimensions of the areas are governed
  by the size of the components added to them.

61
BorderLayout
North
West
East
Center
South
62
Border-LayoutExample

• public class BorderLayoutTest extends JFrame
• JButton b1new JButton("Red"),
• b2new JButton("Green"),b3new JButton("Blue"),
• b4new JButton("Yellow"),b5new JButton("Pink")
• public BorderLayoutTest()
• setTitle("BorderLayout Test")
• Container pane getContentPane()
• pane.setLayout(new BorderLayout())
• setBounds(0,0,400,150)
• pane.add(b1,"North") pane.add(b2,"South") pane
  .add(b3,"East")
• pane.add(b4,"West") pane.add(b5,"Center")
• public static void main(String args)
• JFrame f new BorderLayoutTest()
• f.setVisible(true)

note extra parameter
63
GridLayout

• Components are placed in a grid with a
  user-specified number of columns and rows.
• Each component occupies exactly one grid cell.
• Grid cells are filled left to right and top to
  bottom.
• All cells in the grid are the same size.
• Specifying zero for either rows or columns means
  any number of items can be placed in that row or
  column.

64
GridLayout Example

• public class GridLayoutTest extends JFrame
• JButton b1new JButton("Red"),
• b2new JButton("Green"),b3new JButton("Blue"),
• b4new JButton("Yellow"),b5new JButton("Pink")
• public GridLayoutTest()
• setTitle("GridLayout Test")
• Container pane getContentPane()
• pane.setLayout(new GridLayout(2,3))
• setBounds(0,0,300,100)
• pane.add(b1) pane.add(b2) pane.add(b3)
• pane.add(b4) pane.add(b5)
• public static void main(String args)
• JFrame f new GridLayoutTest()
• f.setVisible(true)

65
CardLayout

• Components governed by a card layout are
  "stacked" such that only one component is
  displayed on the screen at any one time.
• Components are ordered according to the order in
  which they were added to the container.
• Methods control which component is currently
  visible in the container.
• CardLayouts might be appropriate for wizards
  (with the Next gtgt buttons).

66
CardLayout Example (1 of 3)

• public class CardLayoutTest extends JFrame
• implements ActionListener
• JButton b1 new JButton("Red"),b2 new
  JButton("Green"),
• b3 new JButton("Blue"),b4 new
  JButton("Yellow"),
• b5 new JButton("Pink")
• CardLayout lo new CardLayout()
• Container pane
• public CardLayoutTest()
• setTitle("CardLayout Test")
• pane getContentPane()
• pane.setLayout(lo)
• setBounds(0,0,200,100)
• pane.add(b1,"1") pane.add(b2,"2")
  pane.add(b3,"3") pane.add(b4,"4")
  pane.add(b5,"5")
• b1.addActionListener(this)
  b2.addActionListener(this)
• b3.addActionListener(this)
  b4.addActionListener(this)
• b5.addActionListener(this)

67
CardLayout Example (2 of 3)

• // in the same file...
• public void actionPerformed(ActionEvent e)
• if (e.getSource() b1) lo.next(pane)
• else if (e.getSource() b2) lo.next(pane)
• else if (e.getSource() b3) lo.next(pane)
• else if (e.getSource() b4) lo.next(pane)
• else if (e.getSource() b5) lo.next(pane)
• public static void main(String args)
• JFrame f new CardLayoutTest()
• f.setVisible(true)

define the behavior when the user clicks a
button in this case, we advance to the next card
68
CardLayout Example (3 of 3)
Every arrow denotes a button click event. Our
code reacts to the click by advancing to the next
card. Note that the cards cycle.
69
Other Swing Components

• You can see all the other Swing components at
  http//java.sun.com/products/jfc/tsc/articles/comp
  onent_gallery/index.html

70
Creating Your Own Swing Components

• What do you do when none of the existing Swing
  components satisfy your application requirements?
• Make your own!

71
What Triggers Painting?

• System-triggered painting when the system
  requests a component to render its contents. For
  example,
• component is first made visible
• component is resized
• component is damaged and needs repair
• App-triggered painting component decides it
  needs to update its contents because its internal
  state has changed. For example,
• button is depressed
• buttons label changes

72
paint Method

• For both types of triggers, the paint method of
  the component is directly or indirectly called.
• However, you do not override paint!
• The paint method is broken down into three method
  calls
• paintComponent()
• paintBorder()
• paintChildren()
• You override paintComponent!
• Question Why is paintChildren called last?

73
Explicit Paint Requests

• How does a component paint itself when its
  internal state changes (i.e. app-triggered
  painting)?
• Call paint? No!
• You should never call paint directly.
• Instead, call repaint!

74
repaint method

• repaint causes a call to this component's paint
  method as soon as possible.
• It does this by inserting an event into the event
  queue.

75
Double buffering

• Double buffering is when an offscreen buffer is
  used for painting.
• After painting to the offscreen buffer, the final
  results are painted onscreen.
• By default this is set to true.
• Youll probably want this on to ensure smooth GUI
  rendering.
• Without double buffering, painting appears to
  flicker.

Hello
Hello
76
Example Creating Your Own Component (1)

• public class MyComponent extends JComponent
• Color currentColor Color.ORANGE
• public MyComponent()
• super()
• setPreferredSize(new Dimension(40, 40))
• this.addMouseListener(new MouseAdapter()
• public void mouseEntered(MouseEvent e)
• currentColor Color.CYAN
• repaint()
• public void mouseExited(MouseEvent e)
• currentColor Color.ORANGE
• repaint()
• )

77
Example Creating Your Own Component (2)

• public void paintComponent(Graphics g)
• super.paintComponent(g)
• g.setColor(currentColor)
• Dimension d this.getSize()
• g.fillRect(0, 0, (int) d.getWidth(), (int)
  d.getHeight())
• g.setColor(Color.BLACK)
• g.drawRect(0, 0, (int) d.getWidth()-1, (int)
  d.getHeight()-1)
• public static void main(String args)
• JFrame f new JFrame("MyComponent Test")
• f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOS
  E)
• f.getContentPane().add(new MyComponent(),
  BorderLayout.CENTER)
• f.getContentPane().add(new JLabel("Rollover
  this
• orange area!"), BorderLayout.SOUTH)
• f.pack()
• f.setVisible(true)

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Example Summary

• Notice the use of repaint.

During rollover
Before rollover
79
Works Cited

• AWT vs Swing. Borland Developer Network.
  http//bdn.borland.com/article/0,1410,26970,00.htm
  l
• Creating a GUI with JFC/Swing. The Java
  Tutorial. http//java.sun.com/docs/books/tutorial/
  uiswing/index.html
• Implementing Nested Classes. The Java
  Tutorial. http//java.sun.com/docs/books/tutorial
  /java/javaOO/nested.html
• The Java Virtual Machine Specification.
  http//java.sun.com/docs/books/vmspec/2nd-edition/
  html/Concepts.doc.html19152
• What exactly is the Event Dispatch thread (aka
  AWT Thread)? http//www.jguru.com/faq/view.jsp?
  EID8963
• Introducing Swing Architecture.
  http//java.sun.com/products/jfc/tsc/articles/gett
  ing_started/getting_started2.html
• Painting in AWT and Swing. http//java.sun.com/p
  roducts/jfc/tsc/articles/painting/index.html