What You’ll Learn

  1. How to get a JavaFX project up and running fast.
  2. The Application class.
  3. The Stage class.
  4. The Scene class.
  5. Your first Nodes: Label and Region
  6. A little bit about organizing your code.

The Fastest Start Possible

The quickest way to get started is to download this build.gradle file and put it in a directory all by itself.

Now, open it with Intellij Idea. I’m sure you can do the same thing with Eclipse, too.

This should start up a new project. Let it build the Gradle environment and initialize the project. The select the “build->build” option from the Gradle menu.

Now go to the top level of the project and select, “New Directory”. The dialogue box should give you option for the Gradle defined source directories. Highlight them all and hit <Enter>.

Next, if you want to change the group information in build.gradle from “ca.pragmaticcoding”, you should do it now. Then go to the \src\java directory and select “New -> Package”. You should create something like “ca.pragmaticcoding.beginners.part1”.

You’ll need a module-info.java file in the root of the java directory. It should look like this:

module ca.pragmaticcoding.beginners {
    requires javafx.controls;
    requires javafx.graphics;
    requires javafx.base;

    exports ca.pragmaticcoding.beginners.part1;
}

Make sure that you change both references to the package ca.pragmaticcoding.beginners to whatever you are using.

Finally, select that package in the Project listing, and then use the menu “New -> Java Class”, and call it “Main”. Copy the following into it:

import javafx.application.Application;
import javafx.stage.Stage;

public class Main extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) {

    }
}

And there you go! Now we have the skeleton of your first JavaFX application.

Application, Stage and Scene

Let’s take a quick look at this little bit of code, because there’s more going on there than it might seem.

Application

Application is an abstract class that has all of the functionality that gets the JavaFX engine up and running for you. This is all started up when its launch() method is called. Eventually, launch() will call start() which is an abstract method. We’re going to be putting all of our customized code for the application in here.

Stage and Scene

The most mystifying thing when you start with JavaFX is all this Stage and Scene stuff. Simply put, the Stage is the element that corresponds to the window on your screen. If you want to have multiple windows, you’ll generally need to have multiple Stages.

Scene is the component that holds the contents of your window. Why is Scene separate from Stage? I don’t honestly know, and I don’t know what advantage is gained by having the functionality split between two classes.

Ordinarily, you’ll create a Scene and then put a JavaFX Region subclass object inside it. Then you put the Scene inside the Stage, and call the Stage's, show() method.

So let’s do that:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.Region;
import javafx.stage.Stage;

public class Main extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) {
        Scene scene = new Scene(createContent());
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    private Region createContent() {
        return new Label("Hello World");
    }
}

Running the Application

You can run it now. I’d suggest using the “Application -> Run” from the Gradle menu. The output should look like this:

Hello

Not very exciting really, but it is something that runs and opens a window.

Two little pieces of explanation first, and then we’ll conclude Part 1.

You’ll notice that I’ve split createContent() out from the rest of the code in start(), even though it’s really simple. Personally, I think start() should be all about Scene and Stage and getting the window on the screen. The details about the contents of the Scene really don’t belong in start(). Keeping methods small and purposeful is just as important with JavaFX as it is with any other programming.

You should also notice that createContent() returns Label as a Region. Strangely enough, all of the Control classes in JavaFX, including Label extend from Region, even though they don’t seem at first to be Region kind of objects. In the specific case of Label, there’s actually more going on to its structure than you think, and it actually does make sense to think of it as a Region. We’ll look at that later.