Graphical description of Java Notes---event listener

The event listener represents the interface responsible for handling events. Java provides a variety of event listener classes, but we'll talk about those event listener classes that are used more frequently. Each method of an event listener has a parameter as an object that is a subclass of the EventObject class. For example, a mouse event listener method will accept an instance of MouseEvent, where MouseEvent is EventObject derived.

Eventlistner interface

It is a labeled interface, and each listener interface must extend it. This class is defined in the Java.util package.

Event: When an event occurs, there is a corresponding processing scenario.
Event Source Listener Event handling scenario

The elements we added in the frame were clicked without any response, and we needed to add a listener.

Keyboard Event Listener

Import java.awt.Event. Keyadapter;import java.awt.Event. Keyevent;import javax.swing.jbutton;import javax.swing.jframe;import Javax.swing.jlabel;import javax.swing.JPanel; Import Javax.swing.JTextField; Public classDemo05 {Static intCount=0;  Public Static voidMain (string[] args) {JFrame frame=NewJFrame ("form"); JPanel Panel=NewJPanel (); JLabel namelable=NewJLabel ("User name"); JTextField namefiled=NewJTextField (Ten);        Panel.add (namelable);        Panel.add (namefiled);                Frame.add (panel); Namefiled.addkeylistener (NewKeyadapter () {@Override Public voidkeypressed (KeyEvent e) {System. out. println ("pressed characters:"+E.getkeychar ()); System. out. println ("gets the value corresponding to the key:"+E.getkeycode ());        }        }); Demo01.initjframe (Frame, -, -); }}

Graphical description of Java Notes---event listener