Question

The JavaFX framework provides more than one way to handle events. For event handlers, we could use inner classes, anonymous inner classes, or the new Java 8 feature of lambda expressions. In this discussion, you will explore these different ways of writing event handles in JavaFX.

To prepare for this discussion, you must unzip the attached NetBeans project zip file (U4D1_HandleEvents.zip) and load it into your NetBeans IDE. The project uses an inner class to handle the click event on the button node. Rewrite the event handler using either an anonymous inner class, or a lambda expression.

In this discussion:

• Provide a screenshot of your result of your work (code + application output).
• Reflect on your experience and what you learned.

PLEASE Explain, briefly, how you completed this exercise, the algorithm you used (via pseudo code or other description tools), the major issues you faced, and how you solved these issues.

Code below:

package u4d1_handleevents;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class U4D1_HandleEvents extends Application {
  
@Override
public void start(Stage primaryStage) {
Button btn = new Button();
btn.setText("Say 'Hello World'");
  
//using inner class
btn.setOnAction(new MyEventHandler());

StackPane root = new StackPane();
root.getChildren().add(btn);
  
Scene scene = new Scene(root, 300, 250);
  
primaryStage.setTitle("Hello World!");
primaryStage.setScene(scene);
primaryStage.show();
}

class MyEventHandler implements EventHandler<ActionEvent> {
public void handle(ActionEvent event) {
System.out.println("Hello World!");
}   
}
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
launch(args);
}
  
}

Answer 1

Do like and comment if you have any queries.

Below is the modified code for the given question.

Note: Used the code given in the question and modified it.

Code:

    import javafx.application.Application;
   import javafx.event.ActionEvent;
   import javafx.event.EventHandler;
   import javafx.scene.Scene;
   import javafx.scene.control.Button;
   import javafx.scene.layout.StackPane;
   import javafx.stage.Stage;

   public class U4D1_HandleEvents extends Application {
       @Override
       public void start(Stage primaryStage) {
           //creating and inserting button in StackPane layout.
           Button btn = new Button();
           //setting button text as Hello World!.
           btn.setText("Say 'Hello World'");
          
           //using inner class
           btn.setOnAction(new EventHandler<ActionEvent>() {
               @Override
               //function to display message on console when button is pressed.
               public void handle(ActionEvent event) {
                   System.out.println("Hello World!");
               }
           });
          
           //creating StackPane object to arrange nodes on top of another.
           StackPane root = new StackPane();
           //adding button to the stage.
           root.getChildren().add(btn);
           //creating a scene object.
           Scene scene = new Scene(root, 300, 250);
           //setting Hello World! as title to the Stage.
           primaryStage.setTitle("Hello World!");
       //adding scene to the stage.
           primaryStage.setScene(scene);
           //displaying the contents of the stage.
           primaryStage.show();
       }
       /**
       * @param args the command line arguments
       */
       public static void main(String[] args) {
           launch(args);
       }
      
   }

Output Screenshot:

Code Screenshot:

Explanation:

The main aim of the given program is to display hello world! as message when the button is pressed. To do so, first we have to create an object for button using Button() class.Then we have to handle the Event using EventHandler when the button is pressed.After handling the button event, we have to create an object for stackpane (To arrange nodes on top of another).Then we have to add button to the StackPane to display in the button in the application and then we have to create an object for Scene() class to display message into the console.