3 Hello World, JavaFX Style

Construct the Application

1. From the File menu, choose New Project.

2. In the JavaFX application category, choose JavaFX Application. Click Next.

3. Name the project HelloWorld and click Finish.

   NetBeans opens the HelloWorld.java file and populates it with the code for a basic Hello World application, as shown in Example 3-1.

   Example 3-1 Hello World

   package helloworld;
    
   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 HelloWorld extends Application {
       
       @Override
       public void start(Stage primaryStage) {
           Button btn = new Button();
           btn.setText("Say 'Hello World'");
           btn.setOnAction(new EventHandler<ActionEvent>() {
    
               @Override
               public void handle(ActionEvent event) {
                   System.out.println("Hello World!");
               }
           });
           
           StackPane root = new StackPane();
           root.getChildren().add(btn);
   
    Scene scene = new Scene(root, 300, 250);
   
           primaryStage.setTitle("Hello World!");
           primaryStage.setScene(scene);
           primaryStage.show();
       }
    public static void main(String[] args) {
           launch(args);
       }
   }
   

Here are the important things to know about the basic structure of a JavaFX application:

• The main class for a JavaFX application extends the javafx.application.Application class. The start() method is the main entry point for all JavaFX applications.

• A JavaFX application defines the user interface container by means of a stage and a scene. The JavaFX Stage class is the top-level JavaFX container. The JavaFX Scene class is the container for all content. Example 3-1 creates the stage and scene and makes the scene visible in a given pixel size.

• In JavaFX, the content of the scene is represented as a hierarchical scene graph of nodes. In this example, the root node is a StackPane object, which is a resizable layout node. This means that the root node's size tracks the scene's size and changes when the stage is resized by a user.

• The root node contains one child node, a button control with text, plus an event handler to print a message when the button is pressed.

• The main() method is not required for JavaFX applications when the JAR file for the application is created with the JavaFX Packager tool, which embeds the JavaFX Launcher in the JAR file. However, it is useful to include the main() method so you can run JAR files that were created without the JavaFX Launcher, such as when using an IDE in which the JavaFX tools are not fully integrated. Also, Swing applications that embed JavaFX code require the main() method.

Figure 3-1 shows the scene graph for the Hello World application. For more information on scene graphs see Working with the JavaFX Scene Graph.

Run the Application

1. In the Projects window, right-click the HelloWorld project node and choose Run.

2. Click the Say Hello World button.

3. Verify that the text ”Hello World!” is printed to the NetBeans output window.
   Figure 3-2 shows the Hello World application, JavaFX style.

Where to Go Next

This concludes the basic Hello World tutorial, but continue reading for more lessons on developing JavaFX applications:

• Creating a Form in JavaFX teaches the basics of screen layout, how to add controls to a layout, and how to create input events.

• Fancy Forms with JavaFX CSS provides simple style tricks for enhancing your application, including adding a background image and styling buttons and text.

• Using FXML to Create a User Interface shows an alternate method for creating the login user interface. FXML is an XML-based language that provides the structure for building a user interface separate from the application logic of your code.

• Animation and Visual Effects in JavaFX shows how to bring an application to life by adding timeline animation and blend effects.