Chapter 12, Problem 11AW

Event handler:

• The event handler is nothing but an object that responds to the events.
• A particular method in the event handler is called if an event source is connected to the event handler. The object of the event is passed as the argument to that method.
  • This process is known as event firing.
• The event handler class should implement the “EventHandler” interface.
  • This interface is in the package “javafx.event”.

Algorithm to create an event handler class

Step 1: Declare a class named “ButtonClickHandler”.

Step 2: Declare a method named “handle”.

Step 3: Set the text for “outputLabel” as “Hello World”

Event handler class:

//Event handler class

class ButtonClickHandler implements EventHandler <ActionEvent>

{

//Overrides handle class

     @Override

     public void handle(ActionEvent event)

     {

//Set the text

     outputLabel.setText("Hello World");

     }

}

Example program:

The below program demonstrates the Event handler class.

//Import required packages

import javafx.application.Application;

import javafx.event.ActionEvent;

import javafx.event.EventHandler;

import javafx.geometry.Pos;

import javafx.geometry.Insets;

import javafx.stage.Stage;

import javafx.scene.Scene;

import javafx.scene.layout.VBox;

import javafx.scene.control.Label;

import javafx.scene.control.Button;

//Declare the main class

public class Example extends Application

{

//Create a label

private Label outputLabel;

//Declare the main method

public static void main(String[] args)

{

// Launch the application...