Java Programming, Second Edition

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Java Programming, Second Edition

• Chapter Ten
• Graphics

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In this chapter, you will

• Learn about the paint() and repaint() methods
• Use the drawString() method to draw strings
• Use the setFont() and setColor() Graphic object
  methods
• Create Graphics and Graphics 2D objects
• Draw lines, rectangles, ovals, arcs, and polygons

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• Copy an area
• Learn more about fonts and their methods
• Draw with Java 2D graphics
• Add sound, images, and simple animations to Swing
  applets

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Learning about the paint() and repaint() Methods

• paint() method- Runs when Java displays your
  Swing applet
• Is used within every Swing applet
• public void paint (Graphics g)
• repaint() method- Use when a window needs to be
  updated, such as when it contains new images
• Java system calls the repaint() method when it
  needs to update a window
• repaint() creates a Graphics object for you

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Using the drawString() Method to Draw Methods

• drawString() method- Allows you to draw a String
  in a Swing applet window
• Requires three arguments
• A String
• An x-axis coordinate
• A y-axis coordinate

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Using the setFont() and setColor() Graphics
Object Methods

• setFont() and setColor() Graphics object methods-
  Improve the appearance of Graphics objects
• setFont() method requires a Font object
• Font someFont new Font(TimesRoman,Font.BOLD,
  16)

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Using the setFont() and setColor() Graphics
Object Methods

• setColor() method- Color class contains 13
  constants
• Use any of these constants as an argument to the
  setColor() method
• brush.setColor(Color.green)

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The Swing Applets Background Color

• setBackground()
• setBackground(Color.pink)
• Change the background color of your Swing applet
• Do not need a Graphics object to change the Swing
  applets background color

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Creating Graphics and Graphics 2D Objects

• You can instantiate your own Graphics or Graphics
  2D objects

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Drawing Lines

• drawLine() method- To draw a straight line
  between any two points on the screen
• Takes four arguments
• The x- and y-coordinates of the lines starting
  point
• The x- and y-coordinates of the lines ending
  point
• pen.drawLine(10,10,100,200)

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Drawing Rectangles

• drawRect() and fillRect() methods- To draw the
  outline of a rectangle or to draw a solid, or
  filled, rectangle
• These methods require four arguments
• First two represent the x- and y-coordinates of
  the upper-left corner of the rectangle
• Last two represent the width and height of the
  rectangle
• drawRect(20,100,200,10)

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Drawing Rectangles

• clearRect() method- Draws a rectangle
• Requires four arguments
• drawRect() and fillRect() methods use the current
  drawing color
• clearRect() method uses the current background
  color to draw what appears to be an empty or
  clear rectangle

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Drawing Rectangles

• drawRoundRect() method- Create rectangles with
  rounded corners
• Requires six arguments
• x- and y-coordinates of the upper-left corner
• The width and height
• The arc width and height associated with the
  rounded corners

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Drawing Ovals

• drawOval()
• fillOval()
• Both draw ovals using the same four arguments
  that rectangles use

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Drawing Arcs

• Draw an arc using the Graphics drawArc() method
• Provide six arguments
• x-coordinate of the upper-left corner of an
  imaginary rectangle that represents the bounds of
  the imaginary circle that contains the arc
• y-coordinate of the same point
• Width of the imaginary rectangle that represents
  the bounds of the imaginary circle that contains
  the arc
• Height of the same imaginary rectangle
• Beginning arc position
• Arc angle

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Drawing Arcs

• fillArc() method- Creates a solid arc
• Arc is drawn and two straight lines are drawn
  from the arc end points to the center of the
  imaginary circle whose perimeter the arc occupies
• solidarc.fillArc(10,50,100,100,20,320)
• solidarc.fillArc(200,50,100,100,340,40)

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Creating Three-Dimensional Rectangles

• draw3DRect() method- To draw a rectangle that
  appears to have shadowing on two of its edges
• Requires a fifth argument in addition to the x-
  and y-coordinates and width and height
• Fifth argument is a Boolean value
• True if you want the raised rectangle effect
• False if you want the lowered rectangle effect
• fill3DRect() method for creating filled
  three-dimensional rectangles

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Creating Polygons

• drawPolygon() method- To create a shape that is
  more complex than a rectangle
• Requires three arguments two integer arrays and
  a single integer
• First integer array holds a series of
  x-coordinate positions
• Second array holds a series of corresponding
  y-coordinate positions
• Third integer argument is the number of pairs of
  points you want to connect

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Copying an Area

• copyArea() method- Use to copy an area
• Requires 6 parameters
• x-coordinate and y-coordinate of the upper-left
  corner of the area to be copied
• Width and height of the area to be copied
• The horizontal and vertical displacement of the
  destination of the copy

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Learning More about Fonts and Their Methods

• getAllFonts()- Used to discover the fonts that
  are available on your system
• Part of the GraphicsEnvironment class in the
  java.awt package
• getScreenResolution() and getScreenSize()-Used to
  get the resolution and screen size of your system
• getScreenResolution()- returns the number of
  pixels as an int type

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Drawing with Java 2D Graphics

• Java 2D creates higher-quality two-dimensional
  graphics, images, and text
• Includes fill patterns such as gradients
• Strokes that define the width and style of a
  drawing stroke
• Anti-aliasing, a graphics technique for producing
  smoother on-screen graphics

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Specifying the Rendering Attributes

• Fill patterns- Control how a drawing will be
  filled in
• Gradient fill- A gradual shift of color
• Acyclic- color shift occurs once
• Cyclic- color shift occurs repeatedly
• setStroke()- Changes the width of the drawing
  line

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Adding Sound, Images, and Simple Animation to
Swing Applets

• Java 2 supports sound
• Use the play() method to retrieve and play sound
• play() with one argument- the argument is a URL
• play() with two arguments- loads and plays the
  audio file

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Adding Sound, Images, and Simple Animation to
Swing Applets

• Images formats supported by Java include
• Graphics Interchange Format (GIF)
• Maximum of 256 colors
• Join Photographic Experts Group (JPEG)
• Stores mostly photographs
• Portable Network Graphics (PNG)
• Stores images in a lossless form