7/25/2019 Applet Programming

1/23

Applet Programming

7/25/2019 Applet Programming

2/23

What is an Applet?

It is a smalljava program that isaccessed on an internet server,transported over the internet ,automatically installed and run aspart of a web document.

Applet class is contained in

java.appletpackage. All applets are subclasses of Applet

class.

7/25/2019 Applet Programming

3/23

Some important points

!ecutionof an applet doesnotstartwith a mainmethod on rather applethas its own life cycle..

"utput in an applet is not displayedusing println method but usinggraphic methods.

Applet is not e!ecuted using javainterpreter like a normal javaprogram. It is embedded in a web

page.

7/25/2019 Applet Programming

4/23

Applet output window

7/25/2019 Applet Programming

5/23

Applet class methods

voidinit#$ called %rst in beginning

voidstart#$called to start e!ecution

voidpaint#&raphics g$paints outputwindow

voidstop#$ called to suspend e!ecution

voiddestroy#$ called to terminateapplet

booleanisActive#$true if applet started

7/25/2019 Applet Programming

6/23

Applet tag

'A(()*

+"-AS/ codebase01)2

"-/ 3%le name4

+A)*/ aletrnate te!t2

+5A6/ applet name2

WI-*7/ w

7I&7*/ h

+A)I&5/ alignment2

+8S(A/ pi!els2

+7S(A/ pi!els2

9

+'(A1A65A6 / attribute name 8A)0 / value92

: : :

';A(()*9

7/25/2019 Applet Programming

7/23

!ample

import java.awt.

7/25/2019 Applet Programming

8/23

public void start#$

msg E/ 3Inside start C4=D

public void paint#&raphics g$

msg E/ 3Inside paint C4=

g.drawString#msg, F,G$=

D

D

drawString is a method of &raphics class

setackground and setBoreground are inomponent class.

showStatus#String s$ can be used to change

status shown in status window.

7/25/2019 Applet Programming

9/23

olor class constants

olor.gray

olor.blue

olor.black

olor.green

olor.red olor.orange

olor.pink

olor.white

olor.yellow

olor.cyan olor.magenta

olor.darkgray

olor.lightgray

7/25/2019 Applet Programming

10/23

!ample

import java.awt.

7/25/2019 Applet Programming

11/23

public void paint#&raphics g$

g.draw)ine#,, F,F@$= ;;g.draw1ect#F,F,H,@$= ;;

g.%ll1ect#F,F,H,@$= ;;

g.draw1ound1ect#F,F,H,@,F@,F@$=

g.%ll1ound1ect#J,,FK,F,G,K$=;;

D

D

7/25/2019 Applet Programming

12/23

Synta! of these methods

void draw)ine#int start!,int starty,int end!,intendy$=

void draw1ect#int top, int left, int width, int

height$ void %ll1ect#int top, int left, int width, int height$

void draw1ound1ect#int top, int left, int width,int height, int !diameter, int ydiameter$=

void%ll1ound1ect#int top, int left, int width, intheight, int !diameter, int ydiameter$=

if height and width are eLual, it is a sLuare.

7/25/2019 Applet Programming

13/23

-rawing ellipses and circles

void draw"val#int top, int left, intwidth, int height$

void %ll"val#int top, int left, int width,int height$

if height and width are eLual it iscircle, else an ellipse.

7/25/2019 Applet Programming

14/23

-rawing arcs and polygons

void drawArc#int top, int left, int width,int height, int startangle, int endangle$

void %llArc#int top, int left, int width,

int height, int startangle, int endangle$

7/25/2019 Applet Programming

15/23

-rawing (olygons void draw(olygon#int !+2, int y+2, int

num$

void %ll(olygon#int !+2, int y+2, intnum$

where ! and y are arrays of integersand num is the number of vertices inthe polygon.

7/25/2019 Applet Programming

16/23

(assing (arameters

import java.awt.

7/25/2019 Applet Programming

17/23

public void init#$

setackground#olor.green$=

setBoreground#olor.red$=

msg / get(arameter#3message4$=

! / Integer.parseInt#get(arameter#3!position4$=

y / Integer.parseInt#get(arameter#3yposition4$=

Dpublic void paint#&raphics g$

g.drawString#msg, !,y$=showstatus#3Applet (arameters is running4$=

D

D

7/25/2019 Applet Programming

18/23

7*6) %le

'html9

'body9

'applet code / 3(arameters.class4 width / 3>4

height / 3F4 alt / 30se Mava enabled browser4 9'param name / 3message4 value / 3Welcome toMava4 ;9

'param name / 3!position4 value / 3@4 ;9

'param name / 3yposition4 value / 3H4 ;9';applet9

';body9

';html9

7/25/2019 Applet Programming

19/23

*o display a moving banner

import java.awt.

7/25/2019 Applet Programming

20/23

public void start#$

t / new *hread#this$=

Nag / true=

t.start#$=D

public void run#$

char ch=

for# = = $

try

repaint#$=

*hread.sleep#G$=

ch / msg.charAt#$=

msg / msg.substring#F,msg.length#$$=

msg E/ ch=

if#ONag$

break=

Dcatch#Interrupted!ception e$ D

D ;; for loop ends

D ;; run method ends

7/25/2019 Applet Programming

21/23

public void stop#$

Nag / false=t / null=

D

public void paint#&raphics g$

g.drawString#msg,@,@$=

D

D

;; repaint#$ method is de%ned in &raphics classand gives a call to update#$ method of Appletclass which in turn calls paint#$

7/25/2019 Applet Programming

22/23

get-ocumentase#$ returns the directory path containing the

7*6) %le of the applet getodease#$

returns the directory path containing the

applet class %le of the applet

7/25/2019 Applet Programming

23/23

!ample

import java.awt.