How to implement JavaFX event handling using lambda in Java? n



JavaFX Button class provides the setOnAction() method that can be used to set an action for the button click event. An EventHandler is a functional interface and holds only one method is the handle() method.

Syntax

@FunctionalInterface
public interface EventHandler<T extends Event> extends EventListener

In the below example, we can able to implement event handling of JavaFX by using a lambda expression.

Example

import javafx.application.*;
import javafx.beans.property.*;
import javafx.event.*;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.layout.*;
import javafx.stage.*;

public class LambdaWithJavaFxTest extends Application {
   public static void main(String[] args) {
      Application.launch(args);
   }
   @Override
   public void start(Stage stage) throws Exception {
      BorderPane root = new BorderPane();
      ToggleButton button = new ToggleButton("Click");

      final StringProperty btnText = button.textProperty();
      button.setOnAction((event) -> {    // lambda expression
         ToggleButton source = (ToggleButton) event.getSource();
         if(source.isSelected()) {
            btnText.set("Clicked!");
         } else {
            btnText.set("Click!");
         }
      });
      root.setCenter(button);  
      Scene scene = new Scene(root);
      stage.setScene(scene);
      stage.setWidth(300);
      stage.setHeight(250);
      stage.show();
   }
}

Output






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