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Introduction
JavaFX is one of the Java libraries which is freely available and is used to create next-generation client application platforms for desktop, mobile, and other embedded systems which are built on Java. It is lightweight and hardware-accelerated. The JavaFX application is hierarchically categorized into three main components, which are known as Stage, Scene, and nodes. The javafx.application.Application class must be imported in every JavaFX application as it provides various lifecycle methods for the JavaFX application, which are :
Public void init()
Public abstract void start(Stage primaryStage)
Public void stop()
If we wish to create a basic application in JavaFX, we need the following things:
Import javafx.application.Application in our code
Inherit the Application into our class
The start() method of the Application class must be overwritten.
Stage
Similar to Frame in a Swing Application, the JavaFX has the stage. Stage mainly acts as a container for all the JavaFX objects. The platform creates the primary stage internally, while the other stages can be further created by the application. Then we pass the object of the primary stage to the start method. Its the responsibility of the user to call the show method on the object of the primary stage in order to show the primary stage.
It's possible to add objects to the primary stage though they can be added only in a hierarchical way that is, first, the scene graph will be added, and then nodes can be added to that scene graph. A node can be any object of the user's interface, such as text area, buttons, shapes, etc.
Scene
All the methods which are required to deal with a scene object are provided by the javafx.scene.Scene class. The Scene basically holds all the physical contents of a JavaFX application. To be able to visualize the contents on the stage, it is necessary to create a scene.
We must import the javafx.scene package into our code in order to implement the Scene in our JavaFX application. Each scene object can only be added to one stage. The Scene can be easily created using the Scene class object by passing the layout object into the Scene class constructor.
Scene Graph
The scene graph is a collection of various nodes, where a node is an element that can be visualized on the stage and can be anything like a text box, layout, etc. It exists at the lowest level of the hierarchy. Each scene graph has one root, and nodes are implemented in a tree structure. The root node acts as a parent node of all the other nodes that are present in the scene graph. However, the root node may take any of the layouts available in the JavaFX system.
At the lowest level of the tree hierarchy exists the leaf nodes. As each node of the scene graph represents classes of javafx.scene package therefore, we must import it into our application in order to create a fully-featured JavaFX application.
Nodes
JavaFX application contains multiple nodes, where a node is a visual or a graphical primitive object. A node can be anything like a 2D or 3D geometric object (circle, sphere, etc.), container/layout objects (Border Pane, Grid Pane, etc.), or media element objects (audio, video, etc.).
Each node in the scene graph has a parent, if a node does not have a parent, then that is the root node. Similarly, each node can have one or multiple children. A node without any children is known as a leaf node, while the nodes having children are called branch nodes.
Different types of Root Nodes in JavaFX application:
Group: A collective node that has a list of children nodes is called a group node. When a group node is rendered, all of its child nodes get rendered along with it in order. If any transformation or effect state is applied to the group, then it would be applied to all the child nodes too.
Region: it is the base class of all the JavaFX Node-based UI controls.
WebView: It's responsible for managing the web engine and displaying the content.
Leaf Node: A node with no children nodes is known as a leaf node. Some examples of leaf nodes are rectangle, eclipse, box, etc.
Frequently Asked Questions
What is a branch node?
A node that has children is known as a branch node.
What is a leaf node?
A node that has no children is known as a leaf node.
Which component of the JavaFX application structure is similar to the Frame of Swing application.
The Stage component of the JavaFX application structure is similar to the Frame of the swing application.
Conclusion
In this article, we have extensively discussed the Application Structure of JavaFX.
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