Lecture X Swing and Graphics

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G6DHLL High Level Languages
Lecture 17
Dr. Natalio Krasnogor Natalio.Krasnogor_at_Nottingham
.ac.uk
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Today

• Graphics
• When / Why ?
• Painting
• What can be done
• Java 2D
• Sounds
• How to play them
• Full Screen API

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Graphics A BIG topic

• Could run a whole lecture course on how to use
  the various graphics capabilities that Swings
  APIs provide.
• Use the Tutorials and API docs at
• http//java.sun.com/docs/books/tutorial/uiswing/14
  painting/index.html
• http//java.sun.com/docs/books/tutorial/2d/TOC.htm
  ldisplay

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When do I need to use graphics? (1)

• Avoid using graphics if possible
• You may well only need
• icons
• labels and buttons
• borders
• styled text areas
• JEditorPane
• JTextPane

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When do I need to use graphics? (2)

• May need graphics if
• Wish to drastically change apperance of an
  existing component
• Draw shapes to screen
• Draw text to screen
• Animation
• Invent your own component

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Painting (1)

• Component painting
• repaint()
• automatically called when necessary. Eg Window
  unhidden
• revalidate()
• automatically called before repaint when needed.
  Eg when component sizes or position have changed
• Threads and painting
• painting on the event-dispatching thread
• repaint() and revalidate() are thread safe

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Painting (2)

• Double buffering
• Painting performed to off screen buffer, then
  flushed to screen when finished.
• Opaque components
• Improves performance. Time not spent painting
  behind components.
• Shape of painting areas
• always rectangular
• non-opaque (transparent) components can appear
  any shape, although need to use glass panes to
  mask hit detection area

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Painting order

• Visibility based on containment hierarchy
• Background (if opaque)
• Custom painting
• Border
• Child components
• repaints
• if transparent component repaints, all components
  under it must also repaint. This is costly,
  therefore use opaque when possible

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What graphics tools are available in Swing?

• Java AWT Graphics
• Basic but usually enough
• Shapes
• Text
• Images
• Java 2D graphics
• Extends the AWT graphics to provide much more, eg
  gradients, textures etc

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Custom painting (1)

• Occurs between background and border
• Extend component and customise
• JPanel recommended
• e.g. class myPaintingPanel extends JPanel
• can also use atomic components
• e.g. class myPaintingButton extends JButton
• Code goes in overridden paintComponent() method
• public void paintComponent(Graphics g)

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Custom painting (2)

• When writing custom painting code
• should not reproduce painting functionality of
  any other Swing component
• Before doing anything else in paintComponent()
• invoke super.paintComponent() or
• setOpaque(false)

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Painting coordinates

• Component sizes in pixels
• (0,0) at top left corner
• (width-1,height-1) at bottom right corner
• Border sizes (e.g. a 1-pixel border)
• (1,1) at top left
• (width-2, height-2) at bottom right
• General painting area for b pixel border
• b,b w-(b1), h-(b1)

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Getting painting coordinates

• Use component getWidth and getHeight
• Get border sizes with getInsets
• e.g. to get width and height of custom painting
  area use something like
• Insets insets getInsets()
• int currentWidth getWidth() -
  insets.left - insets.right
• int currentHeight getHeight() - insets.top
  - insets.bottom

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Repainting custom paints

• Calling repaint() method requests a repaint to
  occur
• repaint()
• paints whole component any others that need it
  if transparent
• repaint(int leftx,int lefty,int width,int
  height)
• only repaints a specified area
• Component painted after all pending events
  dispatched.
• Painting should be kept short - Done in event
  thread - slows GUI

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Graphics - shapes and text (1)

• Properties stored in Graphics object.
• Represents state
• eg Color, Font, etc
• Methods of Graphics can draw...
• Shapes
• lines, rectangles, 3D rectangles, round-edged
  rectangles, ovals, arcs, polygons
• Text
• Draw string to screen as a graphic

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Graphics - shapes and text (2)

• Drawing a shape on screen
• Use paintComponent Graphics
• void paintComponent(Graphics g)
• super(g)
• g.setColor(Color.RED)
• g.drawRect(x, y, width, height)
• shapes x and y specify upper left

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Graphics - shapes and text (3)

• Drawing a string on screen
• Use paintComponent Graphics again
• void paintComponent(Graphics g)
• super(g)
• g.setFont(new Font(Serif, Font.PLAIN,
  12))
• g.drawSring(Java Swing is _at_!, x, y)
• x and y specify baseline left of text

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Graphics - Images

• Swing Icons by far and away the easiest method of
  displaying graphics.
• If more features needed then use the AWT/Graphics
  functionality
• Supports GIF, PNG and JPEG
• Loading and displaying images
• Image myImage Toolkit.getDefaultToolkit().g
  etImage(filename)g.drawImage(myImage, x, y,
  this)g.drawImage(myImage, x, y, width,
  height,this)

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Tracking Images

• MediaTracker class
• utility class used to track the status of a
  number of images for a particular component.
• Can get information about any errors and
  associated images
• ImageObserver interface
• implemented by all components
• can get use to get notifications about loading
  progress of image as its constructed.

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Java2D API (Graphics2D)

• Provides enhanced image, graphics and text
  capabilities
• Done through extensions to AWT Graphics API
• Amongst others provides
• Hit detection on Shapes text and images
• Complex Printing Support
• Texture rendering
• Complex Shapes/lines

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Java2D Shapes

• Rectangle Shapes
• QuadCurve2D and CubicCurve2D
• GeneralPath
• Arbitary shapes made by connecting lines

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Java 2D - Text

• Often easier to use JLabels since much of the
  work is done for you
• Use the drawString method
• Eg g.drawString(Hello, x, y)
• To set font use setFont method
• Create an instance of Font

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Java 2D - Images

• Much more powerful than basic image display
• Images are best rendered in a Buffer off screen
  as a BufferedImage
• Then drawn to screen with call to
  Graphics2D.drawImage
• Graphics2D provides variety of image filtering
  options
• sharpen/blur, rotate, transform, scale etc

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Java 2D (VERY) Basic use

• Simply cast the Graphics object to Graphics2D
• void paintComponent(Graphics g)
• super(g)
• Graphics g2 (Graphics2D)g.create()
• g2.setColor(Color.BLACK)
• g2.drawRect(x, y, width, height)
• g2.dispose()

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Sounds in Java (1)

• Java sound API under development
• In meantime must use poor alternative
• Need methods from java.applet.Applet
• Can play multiple sound files at same time
• result is mixed to form a composite output
• Plays AIFF, WAV, MIDI, AU and RMF file types
• Code is overly complex for what it does
• inherited from applets hence URL etc...

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Sounds in Java (2)

• Following example plays a sound file sound.wav
• URL soundURL new URL(file//path-to- file/
  sound.wav)
• AudioClip audioClip Applet.newAudioCli
  p(soundURL)
• //then some combination of...
• audioClip.start() //play once
• audioClip.loop() //loop clip till stop
• audioClip.stop() //stop clip playing

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The Full Screen API

• Full Name
• Full Screen Exclusive API
• New to JDK 1.4
• Allows programmer to suspend windowing system and
  draw directly to the screen
• Good for games, slide shows and dedicated
  terminal applications
• Not covered here, but excellent tutorial found
  here
• http//java.sun.com/docs/books/tutorial/extra/full
  screen/index.html

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Summary

• Swing ves
• Swings good because its Platform Independent
• Swing makes it easy to knock up simple GUIs
• Swing ves
• Swing is not always as Platform Independent as it
  claims
• Can get confusing when GUIs get BIG
• Java - its not the fastest language ever...
• When youve finished the cwk youll hate it and
  use JBuilder or some other (better) IDE instead.