Sunday, June 21, 2015

Learning JavaFX on eclipse luna

Today, we will learn JavaFX using eclipse luna as the IDE. It's a start learning journey to get acquainted with the basic of JavaFX in the eclipse development environment. Essentially it is a 'hello world' application. First, let's take a look what is JavaFX. From wikipedia,

JavaFX is a software platform for creating and delivering rich internet applications (RIAs) that can run across a wide variety of devices. JavaFX is intended to replace Swing as the standard GUI library for Java SE, but both will be included for the foreseeable future.[3] JavaFX has support for desktop computers and web browsers on Microsoft Windows, Linux, and Mac OS X.

Okay, so javaFX is a GUI related development arena. With that said, let's start with a simple hello world GUI application for JavaFX. This article assume your java project is using java 8 and eclipse luna and you have setup already. Below is a sample code.

1:  package play.learn.java.fx;  
2:    
3:  import javafx.application.Application;  
4:  import javafx.event.ActionEvent;  
5:  import javafx.event.EventHandler;  
6:  import javafx.scene.Scene;  
7:  import javafx.scene.control.Button;  
8:  import javafx.scene.layout.StackPane;  
9:  import javafx.stage.Stage;  
10:    
11:  public class HelloWorld extends Application {  
12:    
13:     @Override  
14:     public void start(Stage primaryStage) throws Exception {  
15:        Button btn = new Button();  
16:      btn.setText("Say 'Hello World'");  
17:      btn.setOnAction(new EventHandler<ActionEvent>() {  
18:     
19:        @Override  
20:        public void handle(ActionEvent event) {  
21:          System.out.println("Hello World!");  
22:        }  
23:      });  
24:        
25:      StackPane root = new StackPane();  
26:      root.getChildren().add(btn);  
27:        
28:      Scene scene = new Scene(root, 300, 250);  
29:    
30:      primaryStage.setTitle("Hello World!");  
31:      primaryStage.setScene(scene);  
32:      primaryStage.show();  
33:          
34:     }  
35:       
36:     public static void main(String[] args) {  
37:        launch(args);  
38:    
39:     }  
40:  }  


As you can see above, there is a warning about restrict access to the api. To summarize the warning short, it is because non java library is not import by default into the project. So in this situation, you will have to manually add it. It's simple, on the project, right click and then select Properties, then a window pop up and in the Java Build Path tree, click on the 'Add External JARs...' , now you will have to locate where is the java 8 installed, and then select a jar file name jfxrt.jar. It will be relative to where the JAVA_HOME install such that, <JAVA_HOME>/jre/lib/ext/




When that is done, the warning should be dissapear. Now run the application, a window should pop up and click on it, look at the eclipse console, you should see "Hello World!". A little remarks to understand the basic of this application.

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.


The above are excerpt from official documentation. The code can also be found here. That's it, have fun to explore more of JavaFX.

2 comments:

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