JavaFX の setOnAction メソッド

// Importing necessary packages
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

public class FXsetAction extends Application {
  Button Btn; // Decleares a button
  Label lbl; // Decleares a lebel
  Scene scene; // Decleares a scent
  HBox _hbox; // Decleares a Hbox

  public void start(Stage PrimaryStage) throws Exception {
    PrimaryStage.setTitle("JavaFX setOnAction"); // Set the application title
    lbl = new Label("Button not clicked"); // Create a label with default text "No click found"
    Btn = new Button("Click"); // Create a button with label "Click"

    Btn.setOnAction(value -> { // Button action handler function
      lbl.setText("Button Clicked!!!"); // When the button clicked, it will change the lable default
                                        // text from "No click found" to "Clicked!!!".
    });

    _hbox = new HBox(Btn, lbl); // Create a HBox

    scene = new Scene(_hbox, 400, 300); // Create a scene with HBox and necessary height and weight
    PrimaryStage.setScene(scene); // Set scene
    PrimaryStage.show(); // Visualize the application
  }

  public static void main(String[] args) {
    Application.launch(args); // Launch the application
  }
}