Scene Graphs and UI Controls in JavaFX

In JavaFX, a scene graph is a hierarchical structure of nodes that represent the visual elements of a user interface. Nodes in the scene graph can represent UI controls, shapes, images, text, and more. The scene graph is used to define the layout and appearance of the UI, as well as to handle events and perform animations. Here's an overview of scene graphs and UI controls in JavaFX:

Scene Graph

1. Node Hierarchy: Nodes in the scene graph are organized in a hierarchical structure, where each node can have zero or more child nodes. The root of the scene graph is typically a `Scene` object, which represents the top-level container for the UI.

2. Parent-Child Relationships: Nodes can be added as children of other nodes, forming a tree-like structure. Changes to parent nodes, such as layout or visibility changes, automatically propagate to their children.

3. Types of Nodes: JavaFX provides a variety of node types for different purposes, including layout panes (such as `Pane`, `VBox`, and `HBox`), UI controls (such as buttons, labels, and text fields), shapes (such as rectangles, circles, and lines), images, text nodes, and more.

4. Properties and Styles**: Nodes have properties that control their appearance and behavior, such as size, position, color, visibility, and opacity. Nodes can also be styled using CSS to apply custom styles and themes.

UI Controls

1. Button: Represents a button that users can click to trigger an action.

2. Label: Displays a non-editable text or an image.

3. TextField: Allows users to enter and edit text.

4. TextArea: Multi-line text input field.

5. ComboBox: Dropdown menu with a list of selectable items.

6. ListView: Displays a vertical list of items that users can select from.

7. TableView: Displays tabular data in rows and columns.

8. CheckBox: Represents a checkbox that users can toggle on or off.

9. RadioButton: Represents a radio button that users can select from a group of options.

10. ToggleButton: Represents a button that toggles between selected and deselected states.

Example

Here's a simple example demonstrating the use of a scene graph and UI controls in JavaFX:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class HelloWorld extends Application {

    @Override
    public void start(Stage primaryStage) {
        // Create a button
        Button button = new Button("Click Me");

        // Create a layout pane and add the button to it
        StackPane root = new StackPane();
        root.getChildren().add(button);

        // Create a scene and set it on the stage
        Scene scene = new Scene(root, 300, 250);
        primaryStage.setScene(scene);

        // Set the title of the stage and show it
        primaryStage.setTitle("Hello World");
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

In this example, we create a `Button` control and add it to a `StackPane` layout pane. The layout pane is then added to the `Scene`, which is set on the `Stage` (the top-level container for the UI). Finally, we set the title of the stage and show it.

Conclusion

Scene graphs and UI controls are fundamental concepts in JavaFX for building graphical user interfaces. By organizing visual elements in a hierarchical structure and using built-in UI controls, you can create rich and interactive applications with JavaFX. Whether you're building desktop applications, mobile apps, or embedded user interfaces, understanding scene graphs and UI controls is essential for developing JavaFX applications effectively.