Java Methods

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Java Graphics
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Objectives

• Learn about the Java GUI interface.

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Java Graphics

• GUI Graphical User Interface
• AWT Abstract Windowing Toolkit (A collection of
  GUI components implemented using native-platform
  versions of the components)
• Swing GUI components implemented without using
  native code. Swing components have uniform
  behavior on all platforms. Swing components are
  slower than AWT components.

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Heavy Weight Components
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Frame
A Frame is a top-level window with a title and a
border.
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Window

• A Window object is a top-level window with no
  borders and no menubar.
• A window must have either a frame, dialog, or
  another window defined as its owner when its
  constructed.

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JFrame
A JFrame is an extended version of the Frame
class that adds support for the JFC/Swing
component architecture.
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JWindow

• A JWindow object is a top-level window with no
  borders and no menubar.
• A window must have either a frame, dialog, or
  another window defined as its owner when its
  constructed.

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Light Weight Components
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JPanel
A JPanel is a generic light weight component. It
can be used as a container to hold other light
weight components or as a drawing surface.
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Inheritance
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Inheritance

• Inheritance is used extensively in Java graphics.
• Java components are intended to be extended and
  customized.

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Top Down Design
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Java Graphics

• Start JCreator.
• Create a new file called Lab20.java.
• Save the new file in your Lab20 folder.

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Java Graphics

• import java.awt.
• import javax.swing.
• public class Lab20 extends JFrame
• public static void main(String args)
• Lab20 lab new Lab20()
• lab.setVisible(true)
• Lab20()
• setTitle(Boop Boop A Doop)
• setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)

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Java Graphics
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Java Graphics

• Drag The Borders To Resize The Window

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Content Panes
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Content Panes

• JFrame class has several layers (panes) root,
  content, layered, and glass. Programs normally
  reference only the content pane.
• There are two programming idioms for using the
  content pane (1) using the pre-assigned pane, or
  (2) building your own pane.

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Content Panes

• Idiom 1 Use the existing content pane
•  
• Every frame (or window) has a preconstructed
  content pane of class Container. You can get a
  reference to this pane and make changes to it.
•  
• Container content getContentPane() // Use the
  default content pane.
• content.setBackground(Color.BLUE)
• All JFrames already have a content pane, so
  there's no need to create a new one, just get the
  existing pane. And if you're wondering about the
  Container type, it's a superclass of JPanel. In
  fact, if you look at the actual type of the
  object that's currently returned by
  getContentPane(), it actually is a JPanel.

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Content Panes

• Idiom 2 Create your own content pane
•  
• It's common to create a new panel for the content
  pane and tell the window to use this new panel
  for its content pane.
• JPanel content new JPanel() // Create a new
  content pane.
• content.setBackground(Color.BLUE)
• setContentPane(content)

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Java Graphics

• public class Lab20 extends JFrame
• private MyPanel drawingArea new MyPanel()
• private class MyPanel extends JPanel
• public MyPanel()
• setPreferredSize(new Dimension(400, 300))
• setBackground(Color.BLUE)
• public static void main(String args)
• Lab 20 lab new Lab20()
• lab.setVisible(true)
• Lab20()
• setTitle(Boop Boop A Doop)

Nested Class Only nested classes can have private
access.


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Java Graphics
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Graphics Class

• The Graphics class is the abstract base class for
  all graphics contexts that allow an application
  to draw onto components as well as onto
  off-screen images.

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Drawing Basic Shapes
g.drawLine (x1, y1, x2, y2) g.clearRect
(x, y, w, h) g.drawRect (x, y, w, h)
g.fillRect (x, y, w, h) g.drawRoundRect (x,
y, w, h, horzD, vertD) g.fillRoundRect (x,
y, w, h, horzD, vertD) g.drawOval (x, y, w,
h) g.fillOval (x, y, w, h) g.drawArc
(x, y, w, h, fromDegr, measureDegrs)
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Basic Shapes (contd)
g.drawPolygon (xCoords, yCoords, nPoints)
g.fillPolygon (xCoords, yCoords, nPoints)
g.drawPolyline (xCoords, yCoords, nPoints)
g.drawString (str, x, y) g.drawImage (img,
x, y, this)
abc
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ImageObserver, often this
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Coordinate System
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Coordinates
(0, 0)
x
Origin the upper-left corner of the component
Units pixels
y
y-axis points down, as in many other graphics
packages
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Coordinates (contd)

• A GUI component provides getWidth and getHeight
  methods that return its respective dimension.
• These methods can be used to produce scalable
  graphics.
• getWidth and getHeight only work after the
  component has been placed (do not call them from
  a components constructor).

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Coordinates (contd)

• The position of a rectangle, oval, and even an
  arc is defined by using its bounding rectangle,
  described by x, y, width, height

x, y
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Drawing On A JComponent
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paintComponent Method

• When a window becomes visible (uncovered or
  deminimized) or is resized, the "system"
  automatically calls the paintComponent() method
  for all areas of the screen that have to be
  redrawn.
• The paintComponent() method paints the component.
  If this method is reimplemented,
  super.paintComponent() should be called so that
  lightweight components are properly rendered.
• The paintComponent() method should never be
  called directly. Instead, call the repaint()
  method.

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paintComponent Method

• private class MyPanel extends JPanel
• public MyPanel()
• setBackground(Color.BLUE)
• setPreferredSize(new Dimension(400, 300))
• public void paintComponent(Graphics g)

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paintComponent Method
If we want the panel use the established
attributes like background color, we need to call
super.paintComponent.
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paintComponent Method

• public void paintComponent(Graphics g)
• super.paintComponent(g)

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paintComponent Method
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Drawing Basic Shapes
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Drawing Rectangles

• public void paintComponent(Graphics g)
• super.paintComponent(g)
• g.setColor(Color.WHITE)
• g.drawRect(10, 10, 100, 100)

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Drawing Rectangles
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Drawing Rectangles

• public void paintComponent(Graphics g)
• super.paintComponent(g)
• g.setColor(Color.WHITE)
• g.fillRect(10, 10, 100, 100)

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Drawing Rectangles
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Drawing Ovals

• public void paintComponent(Graphics g)
• super.paintComponent(g)
• g.setColor(Color.WHITE)
• g.fillRect(10, 10, 100, 100)
• g.setColor(Color.YELLOW)
• g.fillOval(120, 60, 100, 100)

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Drawing Ovals
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Drawing Polygons

• public void paintComponent(Graphics g)
• super.paintComponent(g)
• g.setColor(Color.WHITE)
• g.fillRect(10, 10, 100, 100)
• g.setColor(Color.YELLOW)
• g.fillOval(120, 60, 100, 100)
• g.setColor(Color.RED)
• int x 30, 70, 90, 50
• int y 30, 30, 90, 90
• g.fillPolygon(x, y, 4)

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Drawing Polygons
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Drawing Polygons

• public void paintComponent(Graphics g)
• super.paintComponent(g)
• g.setColor(Color.WHITE)
• g.fillRect(10, 10, 100, 100)
• g.setColor(Color.YELLOW)
• g.fillOval(120, 60, 100, 100)
• g.setColor(Color.RED)
• int x 30, 70, 50, 90
• int y 30, 30, 90, 90
• g.fillPolygon(x, y, 4)

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Drawing Polygons
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Color Class
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Color Class

• The Color class is used to encapsulate colors in
  the default RGB color space.
• Every color has an implicit alpha value of 1.0 or
  an explicit one provided in the constructor.
• The alpha value defines the transparency of a
  color and can be represented by a float value in
  the range 0.0 - 1.0 or 0 - 255.
• An alpha value of 1.0 or 255 means that the color
  is completely opaque and an alpha value of 0 or
  0.0 means that the color is completely
  transparent.

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Color Class

• The color attribute is set by calling g.setColor
  and stays in effect until changed
• You can form a color with specified red, green,
  and blue (RGB) values

g.setColor(Color.BLUE) g.draw...
g.draw... g.setColor(Color.LIGHT_GRAY)
...
int rVal 5, gVal 255, bVal 40 Color
yourEyes new Color (rVal, gVal, bVal)
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Color Class

• public void paintComponent(Graphics g)
• super.paintComponent(g)
• g.setColor(Color.WHITE)
• g.fillRect(10, 10, 100, 100)
• g.setColor(Color.YELLOW)
• g.fillOval(120, 60, 100, 100)
• g.setColor(Color.RED)
• int x 30, 70, 50, 90
• int y 30, 30, 90, 90
• g.fillPolygon(x, y, 4)
• g.setColor(new Color(255, 200, 200, 128))
• g.fillRect(50, 50, 120, 120)

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Color Class
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Drawing Images
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Drawing Images

• The Graphics class has a drawImage method that
  will draw an image on the graphics context at a
  specified location.
• You have been provided with a Utility class that
  contains a static loadImage method. This method
  will load the specified image file. The file must
  be located in a subfolder called resources.

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Java Graphics

• public class Lab20 extends JFrame
• private MyPanel drawingArea new MyPanel()
• private Image betty Utility.loadImage(betty.jp
  g)
• private class MyPanel extends JPanel
• public MyPanel()
• setPreferredSize(new Dimension(400, 300))
• setBackground(Color.BLUE)

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Drawing Images

• public void paintComponent(Graphics g)
• super.paintComponent(g)
• g.setColor(Color.WHITE)
• g.drawRect(10, 10, 100, 100)
• g.setColor(Color.YELLOW)
• g.fillOval(120, 60, 100, 100)
• g.setColor(Color.RED)
• int x 30, 70, 50, 90
• int y 30, 30, 90, 90
• g.fillPolygon(x, y, 4)
• g.setColor(new Color(255, 200, 200, 128))
• g.fillRect(50, 50, 120, 120)
• g.drawImage(betty, 100, 100, null)

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Drawing Images
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Drawing Text

• The Graphics class has a drawString method that
  will draw text on the graphics context at a
  specified location.

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Drawing Text (cont)
Font font new Font (name, style, size)
g.setFont (font)
abc "Serif" abc
"SansSerif" abc "Monospaced"
int (pixels)
Font.PLAIN Font.BOLD Font.ITALIC
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Drawing Text (cont)

• public void paintComponent(Graphics g)
• super.paintComponent(g)
• g.setColor(Color.WHITE)
• g.fillRect(50, 50, 120, 120)
• g.drawImage(king, 100, 100, null)
• g.setColor(Color.RED)
• g.setFont(new Font(Serif, Font.PLAIN, 24))
• g.drawString(Boop Boop A Doop, 100, 50)

X Position (baseline)
Y Position (baseline)
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Drawing Text (cont)
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Setting The Icon Image
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Setting The Icon Image

• Lab20()
• setTitle(Boop Boop A Doop)
• setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)
• setContentPane(new MyPanel())
• setIconImage(Utility.loadImage(icon.gif))
• pack()

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Setting The Icon Image
Icon
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The AudioClip class
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The AudioClip class

• IMPORT STATEMENT
• import java.applet.
• DEFINE AN INSTANCE FIELD
• private AudioClip clip Utility.loadAudio("m
  usic.wav")
• PLAY THE SOUND
• clip.play() // Plays the sound one time
• OR
• clip.loop() // Plays the sound
  continuously
• STOP THE SOUND
• clip.stop()

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Playing Sounds

• public class Lab20 extends JFrame
• private MyPanel drawingArea new MyPanel()
• private Image betty Utility.loadImage(betty.jp
  g)
• private AudioClip music Utility.loadAudio(musi
  c.wav)
• private class MyPanel extends JPanel
• public MyPanel()
• setPreferredSize(new Dimension(400, 300))
• setBackground(Color.BLUE)

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Playing Sounds (cont)

• Lab20()
• setTitle(Boop Boop A Doop)
• setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)
• setContentPane(drawingArea)
• setIconImage(Utility.loadImage(icon.gif))
• music.play()
• pack()

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Playing Sounds (cont)
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Questions?
Helen Kane
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Begin Lab 20