Creating a User Interface in JavaFX - JavaFX 8: A Definitive Guide to Building Desktop, Mobile, and Embedded Java Clients - page 50

To set the fill property in the OnTheScene example, instead of using one of the constants in the Color class
(e.g., Color.BLUE ), we're using an RGB formula to create the color. Take a look at the javafx.scene.paint.Color class
in the JavaFX API docs and scroll down past the constants such as ALICEBLUE and WHITESMOKE to see the constructors
and methods. We're using a constructor of the Color class, setting the fill property to it, as shown in the following
snippet from Listing 2-2.

sceneRef.setFill(new Color(fillValue, fillValue, fillValue, 1.0));

As you move the Slider, to which the fillVals property is bound, each of the arguments to the Color()
constructor is set to a value from 0 to 255, as indicated in the following code snippet from Listing 2-2.

fillVals.bind(sliderRef.valueProperty());

Populating the Scene with Nodes
As covered in Chapter 1, you can populate a Scene with nodes by instantiating them and adding them to container
nodes (e.g., Group and VBox ) that can contain other nodes. These capabilities enable you to construct complex scene
graphs containing nodes. In the example here, the root property of the Scene contains a Flow layout container, which
causes its contents to flow either vertically or horizontally, wrapping as necessary. The Flow container in our example
contains an HBox (which contains a Slider and a ChoiceBox ) and several other nodes (instances of Text , Hyperlink ,
and RadioButton classes).

Finding a Scene Node by ID
Each node in a Scene can be assigned an ID in the id property of the node. For example, in the following snippet from
Listing 2-2, the id property of a Text node is assigned the String "sceneHeightText" . When the action event handler
in the Hyperlink control is called, the lookup() method of the Scene instance is used to obtain a reference to the node
with the id of "sceneHeightText" . The event handler then prints the content of the Text node to the console.

■ the hyperlink control is essentially a button that has the appearance of hyperlink text. it has an action event
handler in which you could place code that opens a browser page or any other desired functionality.

Note

textSceneH = new Text();
textSceneH.getStyleClass().add("emphasized-text");
textSceneH.setId("sceneHeightText");
Hyperlink hyperlink = new Hyperlink("lookup");
hyperlink.setOnAction((javafx.event.ActionEvent e) -> {
System.out.println("sceneRef:" + sceneRef);
Text textRef = (Text) sceneRef.lookup("#sceneHeightText");
System.out.println(textRef.getText());
});

A close examination of the action event handler reveals that the lookup() method returns a Node , but the actual
type of object returned in this snippet is a Text object. Because we need to access a property of the Text class (text)
that isn't in the Node class, it is necessary to coerce the compiler into trusting that at runtime the object will be an
instance of the Text class.