Java Listener Example

The listener principle is the observer pattern. Just like a star (event source) gathers a group of fans (the observer). When a star is doing something, it is reported through fans. Subscription information, calculator buttons are the application of this principle.

A small example of a listener is written below:

Package listener;
Import Java.util.EventObject;
/**
* Defines the event object that is used to mark the current action. Must inherit EventObject.
* @author Zyj
*
*/
public class Stateevent extends EventObject {


Private static final long serialversionuid = 5323292975415079206L;

Private enum<actionenum> action;

Public Stateevent (Object source, enum<actionenum> action) {
Super (source);
This.action = action;
}


Public enum<actionenum> getaction () {
Return action;
}


public void Setaction (enum<actionenum> action) {
This.action = action;
}

}

Package listener;
public enum Actionenum {
Wake,sleep;
}

Package listener;
Import Java.util.EventListener;
/**
* Defines the listening interface, which is responsible for monitoring stateevent events. Must inherit EventListener.
* @author Zyj
*
*/
Public interface Statelistener extends EventListener {
void Handlestate (Stateevent event);
}

Package listener;
public class Wakelistener implements Statelistener {

@Override
public void Handlestate (Stateevent event) {
if (event.getaction () = null && event.getaction (). Equals (Actionenum.wake)) {
SYSTEM.OUT.PRINTLN ("You wake up! ");
}
}

}

Package listener;
public class Sleeplistener implements Statelistener {

@Override
public void Handlestate (Stateevent event) {
if (event.getaction () = null && event.getaction (). Equals (Actionenum.sleep)) {
System.out.println ("You slept! ");
}
}

}

Package listener;
Import java.util.ArrayList;
Import java.util.List;

public class Statemanager {
Private list<statelistener> List = new arraylist<statelistener> ();

public boolean AddListener (Statelistener listener) {
if (listener = = NULL)
return false;
return List.add (listener);
}

public boolean RemoveListener (Statelistener listener) {
if (listener = = NULL)
return false;
return List.remove (listener);
}

private void Notifyalllisteners (Stateevent event) {
for (Statelistener listener:list) {
Listener.handlestate (event);
}
}

public void Wake () {
Stateevent event = new Stateevent (this, actionenum.wake);
Notifyalllisteners (event);
}

public void sleep () {
Stateevent event = new Stateevent (this, actionenum.sleep);
Notifyalllisteners (event);
}

}

Package listener;
public class Listenertest {
public static void Main (string[] args) {
Statemanager manager = new Statemanager ();
Manager.addlistener (New Wakelistener ());
Manager.addlistener (New Sleeplistener ());
Manager.wake ();
System.out.println ("-----------------");
Manager.sleep ();
}
}

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Java Listener Example