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Java Applet

Java Applet

• (^) Applet is a special type of program that is embedded in the webpage to generate the dynamic content.
• (^) It runs inside the browser and works at client side.
• (^) An applet is a Java program that runs in a Web browser.

Drawback of Applet:

• (^) Plugin is required at client browser to execute applet.
• (^) Java Plug-in extends the functionality of a web browser , allowing applets or Java Beans.

Lifecycle of Java Applet /Architecture/Skeleton

1. Applet is initialized.
2. Applet is started.
3. Applet is painted.
4. Applet is stopped.
5. Applet is destroyed.

java.awt.Component class :

• (^) The Component class provides 1 life cycle method of applet.
• (^) public void paint(Graphics g): is used to paint the Applet.
• (^) It provides Graphics class object that can be used for drawing oval, rectangle, arc etc.

Life cycle program:

• (^) import java.awt.*;
• (^) import java.applet.*;
• (^) /*
• */
• public class AppletTest extends Applet
• {
• public void init() { //initialization }
• (^) public void start () { //start or resume execution }
• (^) public void stop() { //suspend execution }
• (^) public void destroy() { //perform shutdown activity }
• (^) public void paint (Graphics g) { //display the content of window }
• (^) }

Program:

• (^) import java.applet.Applet;
• (^) import java.awt.Graphics;
• (^) /*
• (^)
• (^) */
• (^) public class First extends Applet{
• (^) public void paint(Graphics g){
• (^) g.drawString("welcome",150,150);
• (^) }
• (^) }

APPLET DISPLAY METHODS:

1. void drawstring(String message, int x, int y)
2. void setBackground(Color newColor)
3. void setForeground(Color newColor)

• (^) To set the background color of an applet’s window, we use setBackground( ).
• (^) To set the foreground color, we use setForeground().
• (^) These methods are defined by Component, and have the general forms: void setBackground(Color newColor) void setForeground(Color newColor) Here, newColor specifies the new color.

• (^) The class Color defines the following values that can be used to specify colors:
• (^) Color.black Color.magenta Color.blue Color.orange Color.cyan Color.pink Color.darkGray Color. red Color.gray Color.white Color. green Color.yellow Color.lightGray
• (^) For example, this sets the background color to blue and the text color to yellow: 2. setBackground(Color.blue);
• (^) 3. setForeground(Color.yellow);

Requesting Repaint:

• (^) The repaint( ) method is defined by the AWT.
• (^) whenever your applet needs to update the information displayed in its window, it simply calls repaint().
• (^) It has defined as follows:

1. void repaint( )
2. void repaint(int left , int top , int width , int height )

Repaint() program:

import java.awt.; import java.applet.; /* */ public class SampleBanner extends Applet implements Runnable{ String msg = "A Simple Moving Banner."; Thread t = null; int state; boolean stopFlag; public void init() { setBackground(Color.cyan); setForeground(Color.red); }

public void stop() { stopFlag = true; t = null; } public void paint(Graphics g) { g.drawString(msg, 50, 30); showStatus("This is shown in the status window."); } }

Passing Parameters to Applets :

• (^) We can get any information from the HTML file as a parameter. For this purpose, Applet class provides a method named getParameter(). Syntax: public String getParameter(String parameter Name) The get Parameter() method of the Applet class can be used to retrieve the parameters passed from the HTML page