Applet ppt for higher understanding education
BhanuPriya93439
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20 slides
Jul 08, 2024
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About This Presentation
Ppt on applet
Slide Content
Applet Life Cycle,
Creating Applets.
Creating Applets.
The Class Applet destroy()
init()
start()
stop()
java.applet.Applet
java.awt.Panel
2
init()
start()
stop()
java.applet.Applet
java.awt.Panel
2
3
The Life-Cycle of Applet
init()
Calledexactlyonceinanapplet’slife.
Calledwhenappletisfirstloaded.
Usedtoreadappletparameters,startdownloading
anyotherimagesormediafiles,orsetuptheuser
interface,etc.
start()
Called by the browser or applet viewer to inform
this applet that it should start its execution.
It is called after theinitmethod
The Life-Cycle of Applet
init()
Calledexactlyonceinanapplet’slife.
Calledwhenappletisfirstloaded.
Usedtoreadappletparameters,startdownloading
anyotherimagesormediafiles,orsetuptheuser
interface,etc.
start()
Called by the browser or applet viewer to inform
this applet that it should start its execution.
It is called after theinitmethod
4
Applet Life-Cycle (Cont.)
stop()
Calledbythebrowserorappletviewertoinform
thisappletthatitshouldstopitsexecution.
ItiscalledwhentheWebpagethatcontainsthis
applethasbeenreplacedbyanotherpage,and
alsojustbeforetheappletistobedestroyed.
destroy()
Calledexactlyonce.
Calledwhenthebrowserunloadstheapplet.
Usedtoperformanyfinalclean-up.
Applet Life-Cycle (Cont.)
stop()
Calledbythebrowserorappletviewertoinform
thisappletthatitshouldstopitsexecution.
ItiscalledwhentheWebpagethatcontainsthis
applethasbeenreplacedbyanotherpage,and
alsojustbeforetheappletistobedestroyed.
destroy()
Calledexactlyonce.
Calledwhenthebrowserunloadstheapplet.
Usedtoperformanyfinalclean-up.
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Applet Life-Cycle (Cont.)
init
destroystart
stop
start
Applet Life-Cycle (Cont.)
init
destroystart
stop
start
Applets and applications
AnappletisaJavaprogramthatrunsonawebpage.
AJavaappletisaspecialkindofJavaprogramthatabrowser
enabledwithJavatechnologycanrun.
Anappletistypicallyembeddedinsideawebpage:
Fortestingappletatdevelopmenttime,appletviewercanbeused
torunapplet.
AnapplicationisaJavaprogramthatrunsallbyitself.
main()methodisnotinvokedonanapplet,andanappletclass
willnotdefinemain().
AppletsaredesignedtobeembeddedwithinanHTMLpage.
WhenauserviewsanHTMLpagethatcontainsanapplet,the
codefortheappletisdownloadedtotheuser'smachine.
6
AnappletisaJavaprogramthatrunsonawebpage.
AJavaappletisaspecialkindofJavaprogramthatabrowser
enabledwithJavatechnologycanrun.
Anappletistypicallyembeddedinsideawebpage:
Fortestingappletatdevelopmenttime,appletviewercanbeused
torunapplet.
AnapplicationisaJavaprogramthatrunsallbyitself.
main()methodisnotinvokedonanapplet,andanappletclass
willnotdefinemain().
AppletsaredesignedtobeembeddedwithinanHTMLpage.
WhenauserviewsanHTMLpagethatcontainsanapplet,the
codefortheappletisdownloadedtotheuser'smachine.
6
The Applet class
Tocreateanapplet,wemustimporttheAppletclass.
Thisclassisinthejava.appletpackage.
TheAppletclasscontainscodethatworkswitha
browsertocreateadisplaywindow.
TheonlywaytomakeanappletistoextendApplet.
Example:
import java.applet.Applet;
public class Drawing extends Applet {
…we still need to put some code in here...
}
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Tocreateanapplet,wemustimporttheAppletclass.
Thisclassisinthejava.appletpackage.
TheAppletclasscontainscodethatworkswitha
browsertocreateadisplaywindow.
TheonlywaytomakeanappletistoextendApplet.
Example:
import java.applet.Applet;
public class Drawing extends Applet {
…we still need to put some code in here...
}
7
The paint method
paintdoesn’treturnanyresult.
import java.applet.Applet;
import java.awt.*;
public class Drawing extends Applet {
public void paint(Graphics g) {
…we still need to put some code in here…
}
}
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paintdoesn’treturnanyresult.
import java.applet.Applet;
import java.awt.*;
public class Drawing extends Applet {
public void paint(Graphics g) {
…we still need to put some code in here…
}
}
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Graphics
TheGraphicsclassistheabstractbaseclassforall
graphicscontextsthatallowanapplicationtodraw
ontocomponents.
Methods
publicvoiddrawLine(intx1,inty1,intx2,inty2)
publicvoidfillRect(intx,inty,intwidth,intheight)
publicvoiddrawRect(intx,inty,intwidth,intheight)
publicvoiddrawOval(intx,inty,intwidth,intheight)
publicvoidfillOval(intx,inty,intwidth,intheight)
publicvoiddrawString(Stringstr,intx,inty)
TheGraphicsclassistheabstractbaseclassforall
graphicscontextsthatallowanapplicationtodraw
ontocomponents.
Methods
publicvoiddrawLine(intx1,inty1,intx2,inty2)
publicvoidfillRect(intx,inty,intwidth,intheight)
publicvoiddrawRect(intx,inty,intwidth,intheight)
publicvoiddrawOval(intx,inty,intwidth,intheight)
publicvoidfillOval(intx,inty,intwidth,intheight)
publicvoiddrawString(Stringstr,intx,inty)
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Drawing rectangles
There are two ways to draw rectangles:
g.drawRect(left,top,width,height);
g.fillRect(left,top,width,height);
Drawing rectangles
There are two ways to draw rectangles:
g.drawRect(left,top,width,height);
g.fillRect(left,top,width,height);
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Color
Thejava.awtpackagedefinesaclassnamedColor.
Thereare13predefinedcolors:
Javaalsoallowscolornamesinlowercase:
Color.black,Color.darkGray,etc.
Color.BLACK Color.PINK Color.GREEN
Color.DARK_GRAY Color.RED Color.CYAN
Color.GRAY Color.ORANGE Color.BLUE
Color.LIGHT_GRAY Color.YELLOW
Color.WHITE Color.MAGENTA
Color
Thejava.awtpackagedefinesaclassnamedColor.
Thereare13predefinedcolors:
Javaalsoallowscolornamesinlowercase:
Color.black,Color.darkGray,etc.
Color.BLACK Color.PINK Color.GREEN
Color.DARK_GRAY Color.RED Color.CYAN
Color.GRAY Color.ORANGE Color.BLUE
Color.LIGHT_GRAY Color.YELLOW
Color.WHITE Color.MAGENTA
Java’s coordinate system
Java uses an (x, y) coordinate system
(0, 0) is the top left corner
(50, 0) is 50 pixels to the right of (0, 0)
(0, 20) is 20 pixels down from (0, 0)
(w -1, h -1) is just inside the bottom right corner,
where w is the width of the window and h is its height
12
(0, 0)
(0, 20)
(50, 0)
(50, 20)
(w-1, h-1)
Java uses an (x, y) coordinate system
(0, 0) is the top left corner
(50, 0) is 50 pixels to the right of (0, 0)
(0, 20) is 20 pixels down from (0, 0)
(w -1, h -1) is just inside the bottom right corner,
where w is the width of the window and h is its height
12
(0, 0)
(0, 20)
(50, 0)
(50, 20)
(w-1, h-1)
Some more java.awt methods
g.drawLine(x1, y1, x2, y2);
g.drawOval(left, top, width, height);
g.fillOval(left, top, width, height);
g.drawRoundRect(left, top, width, height);
g.fillRoundRect(left, top, width, height);
g.drawArc(left, top, width, height, startAngle, arcAngle);
g.drawString(string, x, y);
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g.drawLine(x1, y1, x2, y2);
g.drawOval(left, top, width, height);
g.fillOval(left, top, width, height);
g.drawRoundRect(left, top, width, height);
g.fillRoundRect(left, top, width, height);
g.drawArc(left, top, width, height, startAngle, arcAngle);
g.drawString(string, x, y);
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The complete applet
import java.applet.Applet;
import java.awt.*;
public class Drawing extends Applet {
public void paint(Graphics g) {
g.setColor(Color.BLUE);
g.fillRect(20, 20, 50, 30);
g.setColor(Color.RED);
g.fillRect(50, 30, 50, 30);
}
}
The complete applet
import java.applet.Applet;
import java.awt.*;
public class Drawing extends Applet {
public void paint(Graphics g) {
g.setColor(Color.BLUE);
g.fillRect(20, 20, 50, 30);
g.setColor(Color.RED);
g.fillRect(50, 30, 50, 30);
}
}
The HTML page
You can only run an applet in an HTML page.
The HTML looks something like this:
<html>
<body>
<h1>DrawingAppletApplet</h1>
<applet code="Drawing.class"
width="250" height="200">
</applet>
</body>
</html>
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You can only run an applet in an HTML page.
The HTML looks something like this:
<html>
<body>
<h1>DrawingAppletApplet</h1>
<applet code="Drawing.class"
width="250" height="200">
</applet>
</body>
</html>
15
The simplest possible applet
import java.applet.Applet;
public class TrivialApplet extends Applet { }
<applet
code="TrivialApplet.class”
width=200 height=100>
</applet>
TrivialApplet.java
TrivialApplet.html
import java.applet.Applet;
public class TrivialApplet extends Applet { }
<applet
code="TrivialApplet.class”
width=200 height=100>
</applet>
TrivialApplet.java
TrivialApplet.html
The simplest reasonable applet
import java.awt.*;
import java.applet.Applet;
public class HelloWorld extends Applet {
public void paint( Graphics g ) {
g.drawString( "Hello World!", 30, 30 );
}
}
<html>
<applet code ="HelloWorld.class"width =“200" height = “100">
</applet>
</html>
import java.awt.*;
import java.applet.Applet;
public class HelloWorld extends Applet {
public void paint( Graphics g ) {
g.drawString( "Hello World!", 30, 30 );
}
}
<html>
<applet code ="HelloWorld.class"width =“200" height = “100">
</applet>
</html>
Running the applet
Compile
javac HelloWorld.java
If no errors, bytecodes stored in HelloWorld.class
Create an HTML file
ends in .htmor .html(HelloWorld.html)
To execute an applet
appletviewer HelloWorld.html
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Compile
javac HelloWorld.java
If no errors, bytecodes stored in HelloWorld.class
Create an HTML file
ends in .htmor .html(HelloWorld.html)
To execute an applet
appletviewer HelloWorld.html
18
Displaying Numerical values
import java.awt.*;
import java.applet.Applet;
public class abextends Applet{
public void paint(Graphics g){
int a=10, b=20;
int d=a+b;
String s= “sum:“+String.valueOf(d);
g.drawString(s, 100, 100);
}
}
import java.awt.*;
import java.applet.Applet;
public class abextends Applet{
public void paint(Graphics g){
int a=10, b=20;
int d=a+b;
String s= “sum:“+String.valueOf(d);
g.drawString(s, 100, 100);
}
}
Thank You
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