Key Listener Event in Advanced Java Programming

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The KeyListener interface declares methods that handle input from the keyboard. The methods defined in the KeyListener interface are:

1. void keyPressed(KeyEvent ke) Is called when an end user presses a key on the keyboard.
2. void keyReleased(KeyEvent ke) Is called when an end user releases a key on the keyboard.
3. void keyTyped(KeyEvent ke) Is called when an end user types a key on the keyboard, which is the operation of pressing and releasing the key in one fast action.

/* =========================================================== File Name : KeyListenerTest.java WebSite : http://javaproglang.blogspot.in/ Facebook : https://www.facebook.com/AdvanceJavaProgramming Twitter ID : https://twitter.com/AdvanceJava Created By : Bintu Chaudhary =========================================================== */ import java.applet.Applet; import java.awt.*; import java.awt.event.*; /* <APPLET Code="KeyListenerTest" Width=300 Height=300> </APPLET> */ public class KeyListenerTest extends Applet implements KeyListener { String msg[]={"","","","","","","","","",""}; int x=15; int c=x; int y=15; int i=0; public void init() { addKeyListener(this); requestFocus(); } public void keyPressed(KeyEvent ke) { System.out.println(msg); if(c<200) { c=c+5; msg[i]+=ke.getKeyChar(); System.out.println(msg); } else { x=15; y=y+20; c=x; i=i+1; msg[i]+=ke.getKeyChar(); } if(i>9) { for(int k=0;k<10;k++) { msg[0]=""; } x=15; y=15; c=x; i=0; } repaint(); } public void keyReleased(KeyEvent ke) { } public void keyTyped(KeyEvent ke) { } public void paint(Graphics g) { g.drawString(msg[i],x,y); System.out.println(msg); } public void update(Graphics g) { paint(g); } }

The above code shows implementing the KeyListener Interface for accepting input from the keyboard to the applet window. The getKeyChar() method enables taking input from the keybaord and displaying the information in the applet window. The keyPressed method is used for defining the statements that are run when an end user enters input from the keyboard and code will be stored in the file called KeyListenerTest.java, which on compilation will crate a class file called KeyListenerTest.class. Now compile this file using below commands in the DOS mode:

C:\>jdk1.4\bin>javac KeyListenerTest.java
C:\>jdk1.4\bin>appletviewer KeyListenerTest.java

"Output of KeyListenerTest.java"

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