Abstract Window Toolkit

1
Abstract Window Toolkit
2
Abstract Window Toolkit

• class library
• graphics
• lines
• rectangles
• circles
• GUI
• text boxes
• labels
• command buttons

3
Java Application

• javac SomeApp.java
• java SomeApp

compiling
executing
4
Java Application

• execution starts with main

public static void main(String args )
5
Java Applet

• javac SomeApplet.java
• appletviewer SomeApplet.html

compiling
executing
machine code
html source
appletviewer
6
Java Applet

• execution starts with the browser / appletviewer
• browser / appletviewer loads the .class file

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Appletviewer

• executes applet
• utility to test applets
• included with J2SDK

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Java Applet
keyword
public class Intersection extends Applet
class name
base class
class Intersection inherits from base class Applet
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Java Applet
java applet has the following methods
public void init()
public void start()
public void paint(Graphics g)
public void stop()
public void destroy()
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Java Applet
public void init()

• first method called by the browser or appletviewer

• initializes the applet

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Java Applet
public void paint(Graphics g)

• after init()

• refreshing the browser

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HyperText Markup Language (HTML)
width of display area
Class name.html

• lthtmlgt
• ltapplet code class name.class widthwidth
  heightheightgt
• lt/appletgt
• lt/htmlgt

name of class
width of display area
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Java Applet
the following must exist before executing an
applet

• className.html
• className.java
• className.class

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Intersection Example(Intersection.java)

• import java.awt.
• import java.applet.Applet
• public class Intersection extends Applet
• public void paint(Graphics g)
• //draws line from (0,0) to (300,200)
• g.setColor(Color.black)
• g.drawLine( 0, 0, 300, 200)
• //draws line from (300, 0) to (0, 200)
• g.setColor(Color.blue)
• g.drawLine( 300, 0, 0, 200)

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Graphics

• setColor()
• drawLine()
• drawRect()
• drawString()

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setColor
sets color

• g.setColor(Color.black)
• where g is the object

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drawLine()

• draws a line

g.drawLine(
start point x-coordinate,
start point y-coordinate,
end point x-coordinate,
end point y-coordinate
)
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drawLine()
starting point
end point

• g.drawLine( 0, 0, 300, 200)

• method name

• draws a line

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drawRect()

• draws a rectangle based on its coordinates

object.drawRect(
upper left x-coordinate,

• width and height of rectangle should be non
  negative values

upper left y-coordinate,
width of rectangle,
height of rectangle,
)
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drawRect()
width of rectangle,
height of rectangle,
g.drawRect(15, 10, 270, 20)
upper left x-coordinate,
upper left y-coordinate,
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drawString()
draws a string at the specified location
syntax
object.drawString(string, x-coordinate,
y-coordinate)
string to print

• coordinates (or position) at which the string is
  drawn

• coordinates are measured from the upper left
  corner of applet

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drawString
object.drawString(The sum is sum , 25, 25)
string to print
x-coordinate
y-coordinate
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Additional Graphics

• See page 163