APPLET With Demo Example

Applet methods

Basic methods :-

- public void init ()

- public void start ()

- public void stop ()

- public void destroy ()

Other Supplementary methods :-

- public void showStatus(String)

- public String getParameter(String)

How a Java Applet works???

- You write an applet by extending the class Applet

- Applet class defines methods as

- init( )

- start( )

- stop( )

- destroy( )

- and some others…

- These methods do not do anything

- They are stubs

- You make the applet do something by overriding these methods

- You don’t need to override all these methods

- Just the ones you care about

1).Method init( )

- This is the first of your methods to be executed

- It is automatically called by the system when the JVM launches the applet for the first time

- It is only executed once ò It is the best place to

- Initialize variables ø Define the GUI Components ·

E.g. buttons, text fields, scrollbars, etc.

- Lay the components out

- Add listeners to these components

- Pick up any HTML parameters

- Almost every applet you ever write will have an 10 Fall 2007 init( ) of your methods to be executed It is automatically called by the system when the JVM launches the

E.g. buttons, text fields, scrollbars, etc. to these components any HTML parameters Almost every applet you ever write will have an init( ) method

2).Method start( )

- Not usually needed ò It is automatically called after the JVM calls the

- Also called whenever a user returns to the HTML page containing the applet after having gone to other pages

- i.e. each time the page is loaded and restarted

- Can be called repeatedly

- Common place to restart a thread ·

E.g. resuming an animation

- Used mostly in conjunction with stop( )

3).Method stop( )

- Not usually needed

- It is automatically called when the user moves off the page on which the applet sits

- Can be called repeatedly in the same applet

- Called just before destroy( )

- Gives a chance to stop timeconsuming activity the system when the user is not paying attention to the applet

- Should not be called directly

- Used mostly in conjunction with start( )

4).Method destroy( )

- Almost never needed

-Called after stop( )

- The JVM guarantees to call this method when the browser shuts down normally

- Use to explicitly release system resources

- E.g. threads

- System resources are usually released

- Commonly used for reclaiming non13 Fall 2007 destroy( ) The JVM guarantees to call this method when the browser shuts down system resources System resources are usually released automatically memorydependent resources