What is "Node" in JavaFx / FXML?

Question

What is meant by the word "Node" in the context of JavaFx / FXML? If I'm looking for this question, all I find is people using the term discussing something else, but no explanation. For example, this answer to the question: How to open JavaFX FileChooser from a controller class? :

For any node in your scene (e.g. root node, but any node you added @FXML), do

chooser.showOpenDialog(node.getScene().getWindow());

What will be the node, and how in that case will I "enter it using @FXML"?

Answer 1

A Node is a superclass of abstract graphic elements that the script is made of.

Some examples of classes inheriting from Node :

• TextField
• AnchorPane
• Canvas
• Group
• VBox
• Button
• Label
• ...

Entering a Node with the identifier FXMLLoader is performed as follows:

• Create a field in the controller associated with fxml with the appropriate type (i.e. any type that can be assigned the element that you want to insert). This field must be accessible using FXMLLoader , which means it must be public or annotated with @FXML annotation.
• Add the id attribute from the fxml namespace (most likely using the fx prefix) to the element in the fxml file that you want to enter. The value of this attribute is the name of the field in the controller.

Example

FXML

 .... <TextField fx:id="myTextField" ....> .... 

controller

 .... @FXML private TextField myTextField; .... 

FXMLLoader uses this information to assign the object that it creates for this fxml element to a field before invoking the initialize controller method.

A detailed example / advanced tutorial, including injection, can be found here: https://docs.oracle.com/javase/8/javafx/fxml-tutorial/fxml_tutorial_intermediate.htm#JFXMG153

Answer 2

Before you understand what Node , it is also important to first understand that Scene Graph is in JavaFX .

JavaFX applications consist of Stage and Scene or multiple scenes. The stage is the top-level container of your application. A scene, on the other hand, contains all the contents (user interface elements) of your application (if your application has only one "page") or the contents of one of the "pages" of your application and exists in / on the scene. (To be clear here, by page I mean which user is interacting with, for example, the login page.)

The Scene Graph is a graphical illustration of how all the stuff in your scene are laid out. This graph is represented in the form of a tree data structure.

A Node is an item in the scene graph.

I think this image clearly explains this.

An example of Node is Control , which can be any user, for example, TextField, Button, TextArea

Photo loan

Answer 3

This is an old question, but it is answered abstractly. "What is a node?" and "in order to understand what a node is, you must first understand what a scene graph is." A node is a top-level abstract class from which almost everything that is graphically displayed in a graphical interface comes from. His superclass is an Object. In the image presented by Ojonugwa Ochalifu, there is one scene that contains one scene that contains several nodes that contain other nodes. The image displayed in the graphical interface raises the question "How is this created?".

For a general understanding, here are the JavaDocs for Stage, Scene, and EventTarget.
At the javafx doc stage https://docs.oracle.com/javase/8/javafx/api/javafx/stage/Stage.html

and scene https://docs.oracle.com/javase/8/javafx/api/javafx/scene/Scene.html

Both Stage and Scene inherit the same interface, EventTarget, as well as Pane, Control, and a long list of classes. https://docs.oracle.com/javase/8/javafx/api/javafx/event/EventTarget.html

I also recommend looking at the source code for the classes you use. This will help to better understand the behavior of classes inherited from the node. For example, the JavaFX documentation mentions that an error may exist when displaying an image. To prevent this error from occurring in the user interface, thorough testing is required. Another understanding, such as how to access a graph using multi-threaded methods, requires an understanding of how and what the class uses.

The scene graph is contained in the workspace and consists of any subclass of the node. Some nodes, such as panels, may have children. The baby is still a knot. Child elements are contained in a structure that may contain other nodes, which may also have child elements. Thus, the graph is very similar to a multidimensional array or non-binary tree. It is also important to understand that: The scene graph is an Omnidirectional Graph, meaning that the child can access his parent; a child can have only one parent; but can have an unlimited number of children. The getParent () method provides access to the parent node.

Image of the scene graph

Note that essentially the graph structure is a multidimensional array. Or, in other words, an array that can contain either other arrays of elements that inherit from Node, or Nodes, such as ImageViews, Buttons, etc. Arrays like Nodes are Panes, Canvas, etc ... which may contain other nodes.

This is important to understand when it comes to test automation and to reliably ensure that the user interface displays what should be displayed.

A good book to get started with JavaFX is “Learn JavaFX 8” by Kishori Sharan. https://www.amazon.com/Learn-JavaFX-Building-Experience-Interfaces/dp/148421143X/ref=asc_df_148421143X/?tag=bingshoppinga-20&linkCode=df0&hvadid= {creative} & hvpos = {adposition = & hvnet = hvnet random} & hvpone = & hvptwo = & hvqmt = e & hvdev = c & hvdvcmdl = {devicemodel} & hvlocint = & hvlocphy = & hvtargid = PLA-4584413736126928 & PSC = 1