The Basic Applet Life Cycle

1. The browser reads the HTML page and finds any <APPLET> tags.
2. The browser parses the <APPLET> tag to find the CODE and possibly CODEBASE attribute.
3. The browser downloads the .class file for the applet from the URL found in the last step.
4. The browser converts the raw bytes downloaded into a Java class, that is a java.lang.Class object.
5. The browser instantiates the applet class to form an applet object. This requires the applet to have a noargs constructor.
6. The browser calls the applet's init() method.
7. The browser calls the applet's start() method.
8. While the applet is running, the browser passes any events intended for the applet, e.g. mouse clicks, key presses, etc., to the applet's handleEvent() method. Update events are used to tell the applet that it needs to repaint itself.
9. The browser calls the applet's stop() method.
10. The browser calls the applet's destroy() method.

Answered by Raksha , an ibibo Master, at 9:33 AM on June 18, 2008

The Basic Applet Life Cycle

1. The browser reads the HTML page and finds any <APPLET> tags.
2. The browser parses the <APPLET> tag to find the CODE and possibly CODEBASE attribute.
3. The browser downloads the .class file for the applet from the URL found in the last step.
4. The browser converts the raw bytes downloaded into a Java class, that is a java.lang.Class object.
5. The browser instantiates the applet class to form an applet object. This requires the applet to have a noargs constructor.
6. The browser calls the applet's init() method.
7. The browser calls the applet's start() method.
8. While the applet is running, the browser passes any events intended for the applet, e.g. mouse clicks, key presses, etc., to the applet's handleEvent() method. Update events are used to tell the applet that it needs to repaint itself.
9. The browser calls the applet's stop() method.
10. The browser calls the applet's destroy() method.

Answered by Sharad Singh , an ibibo Master, at 3:32 PM on May 27, 2008

The following describes the events that take place when we launch an applet. If you have difficulty understanding any of these points, make sure that you talk to your TA or instructor.

1. The web browser or applet viewer receives a command (from the user) to run a particular applet.
2. The VM that is built-into the browser or viewer starts up, and the compiled version of the applet (the bytecode, which is stored in a .class file somewhere) gets located.
3. The VM starts to interpret the bytecode into the machine language of the computer that we're trying to run the applet on.
4. An Applet object is created. This is done automatically for us, behind the scenes. You don’t need to invoke an Applet constructor in your code, the system takes care of creating the Applet object. This Applet object knows how to respond to all of the messages specified in the Applet class.
5. A series of important Applet methods now gets executed, each method plays a specific role in the set-up and execution of the applet. If your applet code does not contain its own customized versions of these methods, the system will use its own "invisible", default versions instead. If you, the programmer, have supplied your own, more detailed versions of these methods, they will "override" the default versions. (You will understand this issue a lot more when we get to the "Inheritance" lecture later on in the course).
These important methods include:
a) the init() method. The init() method is executed only once, when the applet is first launched, just before it starts running. After creating the Applet object, the init message is sent to the Applet object to initialise the state of the Applet object. For example, suppose we want to have clickable buttons attached to our applet when it is first displayed – these buttons have to be created and then attached to the Applet as part of its state.

b) the start() method. This method performs the task of activating the method, making it actually run. Unlike the init() method, it can be invoked more than once. It is invoked after the init() method when the applet is first launched, and then re-invoked each time the applet needs to be started up again. (For example, the user paused the applet in order to do some other task, but when (s)he returns the applet needs to be started up again. To do this, the system invokes the start() method). In CMPUT 114, you won't usually have worry about including a start() method of your own in your applet code, the default version is usually sufficient.
c) the paint() method is also called after the init() method. The paint() method is responsible for drawing (or "painting") the applet onto the screen for the user to see. The paint() method takes one argument of declared type Graphics:
public void paint(Graphics g) {
When the applet is first launched a Graphics object is automatically created by the system, and a reference to this Graphics object is supplied as an argument for the invokation of the paint() method. You, the programmer, do not have to use a constructor to create the Graphics object, or declare a Graphics instance variable or anything like that. The run-time system takes care of that automatically for us. The Graphics object models the portion of the screen that your applet is going to be displayed on. So when the applet is launched and the init() method has finished executing, the paint() method is given a reference to this automatically-created Graphics object and uses it whenever the paint() method is invoked. The paint method can be called many times - each time we need to re-draw the applet onto the screen, the paint() method gets invoked.
Note: in CMPUT 114 we have a rule which says that students must not use single character identifiers for variable names. Most Java programmers write their paint method signature as given above with the name “g”, but to be c

Answered by Anju Singh , an ibibo Master, at 5:28 PM on May 24, 2008

Here are the lifecycle methods of an Applet:

1. init(): This method is called to initialized an applet

2. start(): This method is called after the initialization of the applet.

3. stop(): This method can be called multiple times in the life cycle of an Applet.

4. destroy(): This method is called only once in the life cycle of the applet when applet is destroyed.

init () method: The life cycle of an applet is begin on that time when the applet is first loaded into the browser and called the init() method. The init() method is called only one time in the life cycle on an applet. The init() method is basically called to read the PARAM tag in the html file. The init () method retrieve the passed parameter through the PARAM tag of html file using get Parameter() method All the initialization such as initialization of variables and the objects like image, sound file are loaded in the init () method .After the initialization of the init() method user can interact with the Applet and mostly applet contains the init() method.

Start () method: The start method of an applet is called after the initialization method init(). This method may be called multiples time when the Applet needs to be started or restarted. For Example if the user wants to return to the Applet, in this situation the start Method() of an Applet will be called by the web browser and the user will be back on the applet. In the start method user can interact within the applet.

Stop () method: The stop() method can be called multiple times in the life cycle of applet like the start () method. Or should be called at least one time. There is only miner difference between the start() method and stop () method. For example the stop() method is called by the web browser on that time When the user leaves one applet to go another applet and the start() method is called on that time when the user wants to go back into the first program or Applet.

destroy() method: The destroy() method is called only one time in the life cycle of Applet like init() method. This method is called only on that time when the browser needs to Shut down.

Answered by manu pal , an ibibo Citizen, at 7:48 AM on May 24, 2008

An applet can react to major events in the following ways:
It can initialize itself.
It can start running.
It can stop running.
It can perform a final cleanup, in preparation for being unloaded.

Answered by Shobhit , an ibibo Master, at 7:09 PM on May 23, 2008

The following describes the events that take place when we launch an applet. If you have difficulty understanding any of these points, make sure that you talk to your TA or instructor.

1. The web browser or applet viewer receives a command (from the user) to run a particular applet.
2. The VM that is built-into the browser or viewer starts up, and the compiled version of the applet (the bytecode, which is stored in a .class file somewhere) gets located.
3. The VM starts to interpret the bytecode into the machine language of the computer that we're trying to run the applet on.
4. An Applet object is created. This is done automatically for us, behind the scenes. You don’t need to invoke an Applet constructor in your code, the system takes care of creating the Applet object. This Applet object knows how to respond to all of the messages specified in the Applet class.
5. A series of important Applet methods now gets executed, each method plays a specific role in the set-up and execution of the applet. If your applet code does not contain its own customized versions of these methods, the system will use its own "invisible", default versions instead. If you, the programmer, have supplied your own, more detailed versions of these methods, they will "override" the default versions. (You will understand this issue a lot more when we get to the "Inheritance" lecture later on in the course).
These important methods include:

a) the init() method. The init() method is executed only once, when the applet is first launched, just before it starts running. After creating the Applet object, the init message is sent to the Applet object to initialise the state of the Applet object. For example, suppose we want to have clickable buttons attached to our applet when it is first displayed – these buttons have to be created and then attached to the Applet as part of its state.

b) the start() method. This method performs the task of activating the method, making it actually run. Unlike the init() method, it can be invoked more than once. It is invoked after the init() method when the applet is first launched, and then re-invoked each time the applet needs to be started up again. (For example, the user paused the applet in order to do some other task, but when (s)he returns the applet needs to be started up again. To do this, the system invokes the start() method). In CMPUT 114, you won't usually have worry about including a start() method of your own in your applet code, the default version is usually sufficient.

c) the paint() method is also called after the init() method. The paint() method is responsible for drawing (or "painting") the applet onto the screen for the user to see. The paint() method takes one argument of declared type Graphics:
public void paint(Graphics g) {
When the applet is first launched a Graphics object is automatically created by the system, and a reference to this Graphics object is supplied as an argument for the invokation of the paint() method. You, the programmer, do not have to use a constructor to create the Graphics object, or declare a Graphics instance variable or anything like that. The run-time system takes care of that automatically for us. The Graphics object models the portion of the screen that your applet is going to be displayed on. So when the applet is launched and the init() method has finished executing, the paint() method is given a reference to this automatically-created Graphics object and uses it whenever the paint() method is invoked. The paint method can be called many times - each time we need to re-draw the applet onto the screen, the paint() method gets invoked.
Note: in CMPUT 114 we have a rule which says that students must not use single character identifiers for variable names. Most Java programmers write their paint method signature as given above with the name “g”, but to be c

Answered by Om Prakash , an ibibo Master, at 6:37 PM on May 23, 2008

An applet can react to major events in the following ways:
It can initialize itself.
It can start running.
It can stop running.
It can perform a final cleanup, in preparation for being unloaded.

Answered by ayisha , an ibibo Master, at 5:26 PM on May 23, 2008

hi blogger Well,


The Life Cycle of An Applet

U often feel uncomfortable with applets because they don't really understand the various methods that they need to include, why these are necessary, and what happens when the VM starts to run an applet. The following describes the events that take place when we launch an applet. If you have difficulty understanding any of these points, make sure that you talk to your TA or instructor.

1. The web browser or applet viewer receives a command (from the user) to run a particular applet.
2. The VM that is built-into the browser or viewer starts up, and the compiled version of the applet (the bytecode, which is stored in a .class file somewhere) gets located.
3. The VM starts to interpret the bytecode into the machine language of the computer that we're trying to run the applet on.
4. An Applet object is created. This is done automatically for us, behind the scenes. You don’t need to invoke an Applet constructor in your code, the system takes care of creating the Applet object. This Applet object knows how to respond to all of the messages specified in the Applet class.
5. A series of important Applet methods now gets executed, each method plays a specific role in the set-up and execution of the applet. If your applet code does not contain its own customized versions of these methods, the system will use its own "invisible", default versions instead. If you, the programmer, have supplied your own, more detailed versions of these methods, they will "override" the default versions. (You will understand this issue a lot more when we get to the "Inheritance" lecture later on in the course).
These important methods include:

a) the init() method. The init() method is executed only once, when the applet is first launched, just before it starts running. After creating the Applet object, the init message is sent to the Applet object to initialise the state of the Applet object. For example, suppose we want to have clickable buttons attached to our applet when it is first displayed – these buttons have to be created and then attached to the Applet as part of its state.

b) the start() method. This method performs the task of activating the method, making it actually run. Unlike the init() method, it can be invoked more than once. It is invoked after the init() method when the applet is first launched, and then re-invoked each time the applet needs to be started up again. (For example, the user paused the applet in order to do some other task, but when (s)he returns the applet needs to be started up again. To do this, the system invokes the start() method). In CMPUT 114, you won't usually have worry about including a start() method of your own in your applet code, the default version is usually sufficient.

c) the paint() method is also called after the init() method. The paint() method is responsible for drawing (or "painting") the applet onto the screen for the user to see. The paint() method takes one argument of declared type Graphics:
public void paint(Graphics g) {
When the applet is first launched a Graphics object is automatically created by the system, and a reference to this Graphics object is supplied as an argument for the invokation of the paint() method. You, the programmer, do not have to use a constructor to create the Graphics object, or declare a Graphics instance variable or anything like that. The run-time system takes care of that automatically for us. The Graphics object models the portion of the screen that your applet is going to be displayed on. So when the applet is launched and the init() method has finished executing, the paint() method is given a reference to this automatically-created Graphics object and uses it whenever the paint() method is invoked. The paint method can be called many times - each time we need to re-draw the applet onto the scree

Answered by laks , an ibibo Master, at 2:59 PM on May 23, 2008

Well,


The Life Cycle of An Applet

U often feel uncomfortable with applets because they don't really understand the various methods that they need to include, why these are necessary, and what happens when the VM starts to run an applet. The following describes the events that take place when we launch an applet. If you have difficulty understanding any of these points, make sure that you talk to your TA or instructor.

1. The web browser or applet viewer receives a command (from the user) to run a particular applet.
2. The VM that is built-into the browser or viewer starts up, and the compiled version of the applet (the bytecode, which is stored in a .class file somewhere) gets located.
3. The VM starts to interpret the bytecode into the machine language of the computer that we're trying to run the applet on.
4. An Applet object is created. This is done automatically for us, behind the scenes. You don’t need to invoke an Applet constructor in your code, the system takes care of creating the Applet object. This Applet object knows how to respond to all of the messages specified in the Applet class.
5. A series of important Applet methods now gets executed, each method plays a specific role in the set-up and execution of the applet. If your applet code does not contain its own customized versions of these methods, the system will use its own "invisible", default versions instead. If you, the programmer, have supplied your own, more detailed versions of these methods, they will "override" the default versions. (You will understand this issue a lot more when we get to the "Inheritance" lecture later on in the course).
These important methods include:

a) the init() method. The init() method is executed only once, when the applet is first launched, just before it starts running. After creating the Applet object, the init message is sent to the Applet object to initialise the state of the Applet object. For example, suppose we want to have clickable buttons attached to our applet when it is first displayed – these buttons have to be created and then attached to the Applet as part of its state.

b) the start() method. This method performs the task of activating the method, making it actually run. Unlike the init() method, it can be invoked more than once. It is invoked after the init() method when the applet is first launched, and then re-invoked each time the applet needs to be started up again. (For example, the user paused the applet in order to do some other task, but when (s)he returns the applet needs to be started up again. To do this, the system invokes the start() method). In CMPUT 114, you won't usually have worry about including a start() method of your own in your applet code, the default version is usually sufficient.

c) the paint() method is also called after the init() method. The paint() method is responsible for drawing (or "painting") the applet onto the screen for the user to see. The paint() method takes one argument of declared type Graphics:
public void paint(Graphics g) {
When the applet is first launched a Graphics object is automatically created by the system, and a reference to this Graphics object is supplied as an argument for the invokation of the paint() method. You, the programmer, do not have to use a constructor to create the Graphics object, or declare a Graphics instance variable or anything like that. The run-time system takes care of that automatically for us. The Graphics object models the portion of the screen that your applet is going to be displayed on. So when the applet is launched and the init() method has finished executing, the paint() method is given a reference to this automatically-created Graphics object and uses it whenever the paint() method is invoked. The paint method can be called many times - each time we need to re-draw the applet onto the screen,

Answered by Ajay Pal , an ibibo Master, at 2:00 PM on May 23, 2008

hi blogger well, An applet is a program written in the Java programming language that can be included in an HTML page, much in the same way an image is included in a page. When you use a Java technology-enabled browser to view a page that contains an applet, the applet's code is transferred to your system and executed by the browser's Java Virtual Machine (JVM). For information and examples on how to include an applet in an HTML page, refer to this description of the <APPLET> tag.
All applets have the following four methods:
public void init();
public void start();
public void stop();
public void destroy();

They have these methods because their superclass, java.applet.Applet, has these methods. (It has others too, but right now I just want to talk about these four.)

In the superclass, these are simply do-nothing methods. For example,

public void init() {}

Subclasses may override these methods to accomplish certain tasks at certain times. For instance, the init() method is a good place to read parameters that were passed to the applet via <PARAM> tags because it's called exactly once when the applet starts up. However, they do not have to override them. Since they're declared in the superclass, the Web browser can invoke them when it needs to without knowing in advance whether the method is implemented in the superclass or the subclass. This is a good example of polymorphism.

Source Site could give you more information :


http://www.cafeaulait.o rg/cour se/week5/27.html

Answered by raj u , an ibibo Master, at 12:34 PM on May 23, 2008