Handling Key Press Event in Java
Introduction
In this section, you will learn about the handling key press event in java. Key
Press is the event is generated when you press any key to the specific
component. This event is performed by the KeyListener.
When you press or release keys for the writing purpose then key events are
fired by the KeyListener objects which generates the KeyEvent environment for
the component.
In this program, you will see how operations are performed when you press the
key to the specific component. Here,
the KeyPress is a constructor of the main class. This constructor
creates a frame and set text field to the panel. Then the panel and the label
have been set to the frame in the program. When you enter the character in the
text field through the
keyboard then your entered data will be displayed in the label. There are
various method have been used to do the required are given :
getKeyChar():
This is the method of the KeyEvent class which determines the
character that has been entered by you. This method returns the character associated
the KeyEvent.
KeyAdapter
This is the class is used to receive the keyboard events. It creates the
keyListener objects using the addKeyListener() method. The generated event is
passed
to every KeyListener objects that receives such types of events using the
addKeyListener() method of the object.
KeyPressed():
This method has been used in the program which receives the
generated event when you press any key to the object. Above method also sets the
text of the
source of the event to the label.
Here is the code of program:
import java.awt.*;
import java.awt.event.*;
public class KeyPress extends Frame{
Label label;
TextField txtField;
public static void main(String[] args) {
KeyPress k = new KeyPress();
}
public KeyPress(){
super("Key Press Event Frame");
Panel panel = new Panel();
label = new Label();
txtField = new TextField(20);
txtField.addKeyListener(new MyKeyListener());
add(label, BorderLayout.NORTH);
panel.add(txtField, BorderLayout.CENTER);
add(panel, BorderLayout.CENTER);
addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent we){
System.exit(0);
}
});
setSize(400,400);
setVisible(true);
}
public class MyKeyListener extends KeyAdapter{
public void keyPressed(KeyEvent ke){
char i = ke.getKeyChar();
String str = Character.toString(i);
label.setText(str);
}
}
}
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