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javafx.scene
Provides the core set of base
classes for the JavaFX Scene Graph API. A scene graph is a tree-like
data structure, where each item in the tree has zero or one parent and
zero or more children.
The two primary classes in this package are:
- {@link javafx.scene.Scene Scene} – Defines the scene to be rendered. It
contains a {@code fill} variable that specifies the background of
the scene, {@code width} and {@code height} variables that
specify the size of the scene, and a {@code content} sequence
that contains a list of "root" {@code Nodes} to be rendered onto
the scene. This sequence of {@code Nodes} is the scene graph for
this {@code Scene}.
A {@code Scene} is rendered onto a {@link javafx.stage.Stage}, which is the
top-level container for JavaFX content.
- {@link javafx.scene.Node Node} – Abstract base class for all nodes in the
scene graph. Each node is either a "leaf" node with no child nodes or
a "branch" node with zero or more child nodes. Each node in the tree
has zero or one parent. Only a single node within each tree in the
scene graph will have no parent, which is often referred to as the
"root" node.
There may be several trees in the scene graph. Some trees may be part of
a {@link javafx.scene.Scene Scene}, in which case they are eligible to be displayed.
Other trees might not be part of any {@link javafx.scene.Scene Scene}.
Branch nodes are of type {@link javafx.scene.Parent Parent} or
subclasses thereof.
Leaf nodes are classes such as
{@link javafx.scene.shape.Rectangle}, {@link javafx.scene.text.Text},
{@link javafx.scene.image.ImageView}, {@link javafx.scene.media.MediaView},
or other such leaf classes which cannot have children.
A node may occur at most once anywhere in the scene
graph. Specifically, a node must appear no more than once in the children
list of a {@link javafx.scene.Parent Parent} or as the clip of a
{@link javafx.scene.Node Node}.
See the {@link javafx.scene.Node Node} class for more details on these restrictions.
Example
An example JavaFX scene graph is as follows:
package example;
import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.Group;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.text.Text;
import javafx.scene.text.Font;
public class Example extends Application {
@Override public void start(Stage stage) {
Group root = new Group();
Scene scene = new Scene(root, 200, 150);
scene.setFill(Color.LIGHTGRAY);
Circle circle = new Circle(60, 40, 30, Color.GREEN);
Text text = new Text(10, 90, "JavaFX Scene");
text.setFill(Color.DARKRED);
Font font = new Font(20);
text.setFont(font);
root.getChildren().add(circle);
root.getChildren().add(text);
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
Application.launch(args);
}
}
The above example will generate the following image:
Coordinate System and Transformations
The {@code Node} class defines a traditional computer graphics "local"
coordinate system in which the {@code x} axis increases to the right and the
{@code y} axis increases downwards. The concrete node classes for shapes
provide variables for defining the geometry and location of the shape
within this local coordinate space. For example,
{@link javafx.scene.shape.Rectangle} provides {@code x}, {@code y},
{@code width}, {@code height} variables while
{@link javafx.scene.shape.Circle} provides {@code centerX}, {@code centerY},
and {@code radius}.
Any {@code Node} can have transformations applied to it. These include
translation, rotation, scaling, or shearing transformations. A transformation
will change the position, orientation, or size of the coordinate system as
viewed from the parent of the node that has been transformed.
See the {@link javafx.scene.Node Node} class for more information on transformations.
Bounding Rectangle
Since every {@code Node} has transformations, every Node's geometric
bounding rectangle can be described differently depending on whether
transformations are accounted for or not.
Each {@code Node} has the following properties which
specifies these bounding rectangles:
- {@code boundsInLocal} – specifies the bounds of the
{@code Node} in untransformed local coordinates.
- {@code boundsInParent} – specifies the bounds of the
{@code Node} after all transformations have been applied.
It is called "boundsInParent" because the
rectangle will be relative to the parent's coordinate system.
- {@code layoutBounds} – specifies the rectangular bounds of
the {@code Node} that should be used as the basis for layout
calculations, and may differ from the visual bounds of the node. For
shapes, Text, and ImageView, the default {@code layoutBounds} includes
only the shape geometry.
See the {@link javafx.scene.Node Node} class for more information on bounding rectangles.
CSS
The JavaFX Scene Graph provides the facility to style nodes using
CSS (Cascading Style Sheets).
The {@link javafx.scene.Node Node} class contains {@code id}, {@code styleClass}, and
{@code style} variables are used by CSS selectors to find nodes
to which styles should be applied. The {@link javafx.scene.Scene Scene} class contains
the {@code stylesheets} variable which is a sequence of URLs that
reference CSS style sheets that are to be applied to the nodes within
that scene.
For further information about CSS, how to apply CSS styles
to nodes, and what properties are available for styling, see the
CSS Reference Guide.