This presentation introduces Java Applet and Java Graphics in detail with examples and finally using the concept of both applet and graphics code the analog clock project to depict how to use them in real life challenges and applications.

1. https://www.facebook.com/Oxus20
oxus20@gmail.com
Java Applet & Graphics
Java Applet
Java Graphics
Analog Clock
Prepared By: Khosrow Kian
Edited By: Abdul Rahman Sherzad

2. Table of Contents
»Java Applet
˃Introduction and Concept
˃Demos
»Graphics
˃Introduction and Concept
»Java Applet Code
2
https://www.facebook.com/Oxus20

3. Java Applet
»An applet is a subclass of Panel
˃It is a container which can hold GUI components
˃It has a graphics context which can be used to draw images
»An applet embedded within an HTML page
˃Applets are defined using the <applet> tag
˃Its size and location are defined within the tag
»Java Virtual Machine is required for the browsers to execute the applet
3
https://www.facebook.com/Oxus20

4. Java Applets vs. Applications
»Applets - Java programs that can run over the Internet using a browser.
˃The browser either contains a JVM (Java Virtual Machine) or loads the Java plugin
˃Applets do not require a main(), but in general will have a paint().
˃An Applet also requires an HTML file before it can be executed.
˃Java Applets are also compiled using the javac command, but are run either with a browser or with the applet viewer command.
»Applications - Java programs that run directly on your machine.
˃Applications must have a main().
˃Java applications are compiled using the javac command and run using the java command.
4
https://www.facebook.com/Oxus20

5. Java Applets vs. Applications
Feature
Application
Applet
main() method
Present
Not present
Execution
Requires JRE
Requires a browser like Chrome, Firefox, IE, Safari, Opera, etc.
Nature
Called as stand-alone application as application can be executed from command prompt
Requires some third party tool help like a browser to execute
Restrictions
Can access any data or software available on the system
cannot access any thing on the system except browser’s services
Security
Does not require any security
Requires highest security for the system as they are untrusted
5
https://www.facebook.com/Oxus20

6. Java Applet Advantages
»Execution of applets is easy in a Web browser and does not require any installation or deployment procedure in real-time programming.
»Writing and displaying (just opening in a browser) graphics and animations is easier than applications.
»In GUI development, constructor, size of frame, window closing code etc. are not required.
6
https://www.facebook.com/Oxus20

7. Java Applet Methods
»init()
˃Called when applet is loaded onto user’s machine.
»start()
˃Called when applet becomes visible (page called up).
»stop()
˃Called when applet becomes hidden (page loses focus).
»destroy()
˃Guaranteed to be called when browser shuts down.
7
https://www.facebook.com/Oxus20

8. Introduction to Java Graphics
»Java contains support for graphics that enable programmers to visually enhance applications
»Java contains many more sophisticated drawing capabilities as part of the Java 2D API
˃Color
˃Font and FontMetrics
˃Graphics2D
˃Polygon
˃BasicStroke
˃GradientPaint and TexturePaint
˃Java 2D shape classes
8
https://www.facebook.com/Oxus20

9. 9
https://www.facebook.com/Oxus20

10. Java Coordinate System
»Upper-Left Corner of a GUI component has the coordinates (0, 0)
»X-Coordinate (horizontal coordinate)
˃horizontal distance moving right from the left of the screen
»Y-Coordinate (vertical coordinate)
˃vertical distance moving down from the top of the screen
»Coordinate units are measured in pixels.
˃A pixel is a display monitor’s smallest unit of resolution.
https://www.facebook.com/Oxus20
10

11. All Roads Lead to JComponent
»Every Swing object inherits from JComponent
» JComponent has a few methods that can be overridden in order to draw special things
˃public void paint(Graphics g)
˃public void paintComponent(Graphics g)
˃public void repaint()
»So if we want custom drawing, we take any JComponent and extend it...
˃JPanel is a good choice
11
https://www.facebook.com/Oxus20

12. Draw Line Example
import java.awt.Graphics;
import javax.swing.JApplet;
public class DrawLine extends JApplet {
@Override
public void init() {
}
public void paint(Graphics g){
g.drawLine(20,20, 100,100);
}
}
https://www.facebook.com/Oxus20
12

13. Draw Rectangles Example
import java.awt.Graphics;
import javax.swing.JApplet;
public class DrawRect extends JApplet {
@Override
public void init() {
super.init();
}
public void paint(Graphics g) {
g.drawRect(20, 20, 100, 100);
g.fillRect(130, 20, 100, 100);
g.drawRoundRect(240, 20, 100, 100, 10, 10);
}
}
https://www.facebook.com/Oxus20
13

14. Draw Ovals Example
import java.awt.Graphics;
import javax.swing.JApplet;
public class DrawOval extends JApplet {
@Override
public void init() {
}
public void paint(Graphics g) {
g.drawOval(20, 20, 100, 100);
g.fillOval(130, 20, 100, 100);
}
}
https://www.facebook.com/Oxus20
14

15. Simple Calculator Example
import java.applet.Applet;
import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.Panel;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Calculator extends Applet implements ActionListener {
String operators[] = { "+", "-", "*", "/", "=", "C" };
String operator = "";
int previousValue = 0;
Button buttons[] = new Button[16];
TextField txtResult = new TextField(10);
15
https://www.facebook.com/Oxus20

16. public void init() {
setLayout(new BorderLayout());
add(txtResult, "North");
txtResult.setText("0");
Panel p = new Panel();
p.setLayout(new GridLayout(4, 4));
for (int i = 0; i < 16; i++) {
if (i < 10) {
buttons[i] = new Button(String.valueOf(i));
} else {
buttons[i] = new Button(operators[i % 10]);
}
buttons[i].setFont(new Font("Verdana", Font.BOLD, 18));
p.add(buttons[i]);
add(p, "Center");
buttons[i].addActionListener(this);
}
}
16
https://www.facebook.com/Oxus20

17. public void actionPerformed(ActionEvent ae) {
int result = 0;
String caption = ae.getActionCommand();
int currentValue = Integer.parseInt(txtResult.getText());
if (caption.equals("C")) {
txtResult.setText("0");
previousValue = 0;
currentValue = 0;
result = 0;
operator = "";
} else if (caption.equals("=")) {
result = 0;
if (operator == "+")
result = previousValue + currentValue;
else if (operator == "-")
result = previousValue - currentValue;
else if (operator == "*")
result = previousValue * currentValue;
else if (operator == "/")
result = previousValue / currentValue;
txtResult.setText(String.valueOf(result));
}
17
https://www.facebook.com/Oxus20

18. End - Simple Calculator Example
else if (caption.equals("+") || caption.equals("-")
|| caption.equals("*") || caption.equals("/")) {
previousValue = currentValue;
operator = caption;
txtResult.setText("0");
} else {
int value = currentValue * 10 + Integer.parseInt(caption);
txtResult.setText(String.valueOf(value));
}
}
}
18
https://www.facebook.com/Oxus20

19. OUTPUT - Simple Calculator Example
19
https://www.facebook.com/Oxus20

20. Example of Graphics and Applet
20
https://www.facebook.com/Oxus20

21. Analog Clock Example
21
https://www.facebook.com/Oxus20
import java.applet.Applet;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.util.Calendar;
public class AnalogClock extends Applet implements Runnable {
private static final long serialVersionUID = 1L;
private static final double TWO_PI = 2.0 * Math.PI;
private Calendar nw = Calendar.getInstance();
int width = 200, hight = 200;
int xcent = width / 2, ycent = hight / 2;
int minhand, maxhand;
double rdns;
int dxmin, dymin, dxmax, dymax;
double radins, sine, cosine;
double fminutes;
Thread t = null;
Boolean stopFlag;

22. 22
https://www.facebook.com/Oxus20
public void start() {
t = new Thread(this);
stopFlag = false;
t.start();
}
public void run() {
for (;;) {
try {
updateTime();
repaint();
Thread.sleep(1000);
if (stopFlag)
break;
} catch (InterruptedException e) {
}
}
}
public void stop() {
stopFlag = true;
t = null;
}
private void updateTime() {
nw.setTimeInMillis(System.currentTimeMillis());
}

23. 23
https://www.facebook.com/Oxus20
public void paint(Graphics g) {
g.setFont(new Font("Gabriola", Font.BOLD + Font.ITALIC, 160));
g.setColor(Color.RED);
g.drawString("XUS", 300, 270);
g.setFont(new Font("Consolas", Font.BOLD + Font.ITALIC, 100));
g.setColor(Color.GREEN);
g.drawString("20", 550, 270);
g.setColor(Color.black);
g.fillOval(100, 100, 200, 200);
Graphics2D g1 = (Graphics2D) g;
int hours = nw.get(Calendar.HOUR);
int minutes = nw.get(Calendar.MINUTE);
int seconds = nw.get(Calendar.SECOND);
int millis = nw.get(Calendar.MILLISECOND);
minhand = width / 8;
maxhand = width / 2;
rdns = (seconds + ((double) millis / 1000)) / 60.0;
drw(g1, rdns, 0, maxhand - 20);
g1.setColor(Color.BLUE);
g1.drawString(
String.format("%02d : %02d :%02d ", hours, minutes, seconds),
minhand + 150, maxhand + 170);

24. 24
https://www.facebook.com/Oxus20
minhand = 0; // Minute hand starts in middle.
maxhand = width / 3;
fminutes = (minutes + rdns) / 60.0;
drw(g1, fminutes, 0, maxhand);
minhand = 0; // Minute hand starts in middle.
maxhand = width / 4;
drw(g1, (hours + fminutes) / 12.0, 0, maxhand);
g1.setColor(Color.gray); // set b ackground of circle
g1.drawOval(100, 100, 200, 200); // draw a circle
g1.setColor(Color.WHITE);
g1.setFont(new Font("Consulas", Font.BOLD + Font.ITALIC, 15));
g1.drawString("12", 190, 120);
g1.drawString("6", 195, 290);
g1.drawString("3", 280, 200);
g1.drawString("6", 110, 200);
g1.setFont(new Font("Consulas", Font.BOLD + Font.ITALIC, 15));
g1.setStroke(new BasicStroke(2, BasicStroke.JOIN_MITER,
BasicStroke.JOIN_BEVEL));
}

25. End - Analog Clock Example
public void drw(Graphics2D g, double prct, int minRadius, int maxRadius) {
radins = (0.5 - prct) * TWO_PI;
sine = Math.sin(radins);
cosine = Math.cos(radins);
dxmin = xcent + (int) (minRadius * sine);
dymin = ycent + (int) (minRadius * cosine);
dxmax = xcent + (int) (maxRadius * sine);
dymax = ycent + (int) (maxRadius * cosine);
g.setColor(Color.WHITE);
g.setBackground(Color.cyan);
g.setFont(new Font("Consulas", Font.BOLD + Font.ITALIC, 12));
g.drawLine(dxmin + 100, dymin + 100, dxmax + 100, dymax + 100);
}
}
25
https://www.facebook.com/Oxus20

26. OUTPUT - Analog Clock Example
26
https://www.facebook.com/Oxus20

27. END
https://www.facebook.com/Oxus20
27