3. applets

IMRAN DAUD
FOUNDATION UNIVERSITY
INSTITUTE OF MANAGEMENT AND
COMPUTER SCIENCES
Imran Daud
FUIMCS
Web Engineering
Java Applets

Applets
 An applet is a Java program that a browser can
download and run.
 An applet is embedded inside a web page and runs in
the context of a browser.
 An applet must be a subclass of the
java.applet.Applet class.
 Swing provides javax.swing.JApplet.

Sample Applet Code
 Two steps to turning it in to an Applet
 1. Change "extend JFrame" to "extends JApplet" and get rid of the main, you'll have to

 import javax.swing.JApplet
 public class MyApp extends JApplet {
 ...
 } // end MyApp

 2. Embed the application into the webpage, using html

 <html>
 <head>
 <title> My Applet </title
 </head>
 <body>
 <! this is the applet tag which has attributes, there must be code, width, height>
 <applet code = "MyApp.class” width = "300” height = "300”>
 <! there can be optional parameters >
 <param name="someParamName" value="paramStringValue" >
 </applet>
 </body>
 </html>

Applet Life Cycle
 loaded -> created -> initialized -> started <=> stopped -> destroyed
 The applet maybe stopped because the user has changed focused
 JApplet has methods initialized, started, stopped and destroyed phases.
They have default behavior that you can over write.
 init() - this where you can load the parameter, someParamName, with their
String values using getParamter("someParamName"). Note that order is
not important.
 start() - here you can start things after stopping
 stop() - allows you save information before stopping and to use in start()
 destroy() - allows you clean up. Note stop will be called first.

Applets have restrictions:
 Cannot read or write files on the client machine
 Cannot run programs on the client machine
 Cannot make any computer connections
But the Applet can read data files on the Sever

Steps to create Applet Projects in
Netbeans
 Choose File > New Project (Ctrl-Shift-N). Under
Categories, select Java.
 Choose one of the following:
 If you are creating a new applet source file, select Java Class
Library under Projects. Click Next.
 If you want to import an applet source file, select Java Project
with Existing Sources. Click Next. Specify the file's location in
the Source Packages Folder text box.
 Under Project Name, type HelloApplet. Change the
Project Location to any folder on your computer.
 Click Finish.

Create applet source file
 Right-click the HelloApplet project and choose Properties
to open the Properties window.
 Select the desired Source / Binary Format for the project
from source tab.
 Right-click the HelloApplet project node in the Projects
window and select New > Other (Ctrl-N).
 Under Categories, select Java. Under File Types, select
Applet.
 (for visual design applet select Swing GUI Forms > JApplet
Form.)
 Give name to applet and click finish.

Demo
 Init()
 Start()
 Stop()
 Destroy()

Setting ground for applet
 Set all static parameters in init() function. Like
 Setsize(int width, int height)
 Setbackgroundcolor()

Drawing Shapes
 Rectangle
 Oval
 Etc (consult documentation)

Adding Mouse
 MouseListener
 MouseMotionListener
 (Consult API Documentation for function details)

Keyboard Input
 KeyListener
 actionListener
 (Consult API Documentatio)

 Panel
 JTextField
 JTextArea
 JCombobox
 etc

Java Layouts
 FlowLayout
 BorderLayout
 GridLayout
 BoxLayout
 CardLayout
 GridBagLayout
 GroupLayout
 SpringLayout

Threads
 Thread --- Class
 Runnable ---- Interface

Class --- Thread
 Public Class A extends Thread{
 Public void run(){
 }
 }
 A aa= new A();
 aa.start();

Runnable
 Public class A implements Runnable{
 Public void run(){
 }
 }
 A aa = new A();
 Thread t1 = new Thread(aa);
 t1.start();

Reference
 http://www.csl.mtu.edu/cs2321/
 Netbeans.org

3. applets

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