In the previous article, we have already learned about basics of applet.
Life Cycle of applet
1. init() : init method is used to initialize the applet. Before doing anything, must to initialized, so same thing with the applet. Like, in the games.
Before play any games, must to initialized all the drivers in the system, which is necessary for the games. In the applet, init method is invoked only once, also that method invoked after param tag, which is inside in <applet></applet> tag.
2. start() : This is invoked after the initialization completed. It is used to start the applet, also automatic start. When user navigate to the web page, if
web page contain applet code then it start automatically also start when user moves from other web pages.
3. paint () : This method is invoked just after start() method. Actually only this method is responsible to design the applet, also responsible for repaint the browser, if applet is stooped. It has contain graphics argument as a parameter, through Graphics class we can design any graphics in the applet like rectangle, oval etc. Graphics class inherit from java.awt class.
4. stop() : This method is invoked, just after when the user moves to other browser tab from current applet tab.
5. destroy() : This method is invoked only that time when user close the browser. You can say, opened web page contain applet code , on that time applet is running
properly but in case if user close the browser, applet instance is automatically deleted from the page and destroy method is called automatically.
Example of Applet
The following is a simple applet named HelloWorld.java
import java.applet.*;
import java.awt.*;
public class HelloWorld extends Applet
{
public void paint (Graphics g)
{
g.drawString ("Hello World", 30, 50);
}
}
The first line of code define, imports some packages, which is used for design the applet. Here are two class that is applet and awt. In the second line of code, we have a class "HelloWorld" which is inherited from Applet class. This Applet class inside in java.applet.* package. Through the Graphics class, we can design new object in the applet. This class inherited from java.awt.*. In this example, we have to draw a string with height and width argument(width=30, height=50).
With the help of applet tag, we will show the output in any browser, which support applet. Applet tag is:
<applet code="HelloWorld.class" width=50 height=60></applet>
This tells the viewer or browser to load the applet whose compiled code is in HelloWorld.class (in the same directory as the current HTML document), and to set the initial size of the applet to 50 pixels wide and 60 pixels high.