Application Development using JAVA

​

Hierarchy & Life cycle of Applets

​

Smt.M.Jeevana Sujitha

Assistant Professor

​

Department of Computer Science and Engineering

SRKR Engineering College, Bhimavaram, A.P. - 534204

OBJECTIVES

The Objectives of this lecture are

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• To learn about hierarchy of applets.
• To learn about life cycle of an applet.

Hierarchy of Applet

• java.lang.Object
• java.awt.Component
• java.awt.Container
• java.awt.Panel
• java.awt.Applet

Life cycle of Applet

Life cycle of Applet

• The applet states include
• Initialization state
• Running state
• Idle or stopped state
• Dead state
• Display state

Life cycle of Applet

• Initialization state: Applet enters the initialization state when it is first loaded.
• It is achieved by calling the init() method of Applet class.
• The initialization occurs only once in the life cycle of applet.
• At initialization state we can setup initial values, load images and setup colors.

Syntax:

public void init()

{

Action

}

Life cycle of Applet

• Running state: Applet enters the Running state when the system calls the start() of Applet class.
• This occurs automatically after the applet is initialized.
• The start() method is called more than once. Syntax:

public void start()

{

Action

}

Life cycle of Applet

• Idle or stopped state: An applet becomes idle when it is stopped from running.
• Stopping occurs automatically when we leave the page containing the currently running applet.
• We can also stop the currently running applet by using stop() method explicitly.

Syntax:

public void stop()

{

Action

}

Life cycle of Applet

• Dead state: An applet is said to be dead when it is removed from memory.
• This occurs automatically when we quit from the browser or by calling destroy() method.
• Like initialization destroying stage occurs only once in the applet life cycle.
• We may override the destroy() method to cleanup the resources.

Syntax:

public void destroy()

{

Clean up code

}

Life cycle of Applet

• Display state: An applet moves to the display state whenever it has to perform some output operations on the screen.
• This happens immediately after the applet enters into the running state.
• The paint() method is called to accomplish this task.

Syntax:

public void paint(Graphics g)

{

Display statements

}

THANK YOU