What You Need to Know about the Scene Class in JavaFX - dummies

What You Need to Know about the Scene Class in JavaFX

By Doug Lowe

Like the Stage class, the Scene class is fundamental to JavaFX programs. In every JavaFX program, you use at least one instance of the Scene class to hold the user-interface controls that your users will interact with as they use your program.

This table lists the more commonly used constructors and methods of the Scene class.

Commonly Used Constructors and Methods of the Scene class
Constructor Description
Scene(Parent root) Creates a new scene with the specified root node
Scene(Parent root, double width, double height) Creates a new scene with the specified root node, width, and height
Method Description
double getHeight() Gets the height of the scene
double getWidth() Gets the width of the scene
double getX() Gets the horizontal position of the scene
double getY() Gets the vertical position of the screen
void setRoot(Parent root) Sets the root node

The following paragraphs explain some of the more interesting details of the constructors and methods of the Scene class:

  • All the Scene class constructors require that you specify the root node.

You can change the root node later by calling the setRoot method, but it’s not possible to create a scene without a root node.

  • You might be wondering why the root node is an instance of the Parent class rather than an instance of the Node class. The Parent class is actually a subclass of the Node class, which represents a node that can have child nodes. There are several other subclasses of Node, which represent nodes that can’t have children; those nodes can’t be used as the root node for a scene.
  • You can set the scene’s initial size when you create it by specifying the Width and Height parameters.

If you don’t set the size, the scene will determine its own size based on its content.

  • You can retrieve the size of the scene via the getHeight and getWidth methods.

There are no corresponding set methods that let you set the height or width.

  • In general, the size of the scene determines the size of the stage, provided that that scene is not smaller than the minimum size specified for the stage or larger than the maximum size.
  • If the user resizes the stage, the size of the scene is resized accordingly.