Chapter 12, Problem 13AW

Explanation of Solution

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 register an instance of the class with “myButton” control using lambda expression:

Step 1: Register the event handler for the button using “setOnAction ()” method.

Step 2: Inside this, set the text for the label as “Hello World”.

Statement to register an instance of the class with “myButton” control using lambda expression:

//Register the event handler

myButton.setOnAction(event ->

{

//Set the text

outputLabel.setText("Hello World");

});

Example program:

The statement to register the event handler for “myButton” is highlighted.

//Import required packages

import javafx.application.Application;

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

{

//Declare the main method

public static void main(String[] args)

{

// Launch the application...