fx:subclass attribute

The fx:subclass attribute identifies the fully-qualified name of the code-behind class. The FXML compiler generates a base class which must be extended by the code-behind class. Embedded markup in a @ComponentView annotation uses the annotated class as its code-behind class automatically, so fx:subclass is neither required nor supported in this scenario.

The generated base class contains an initializeComponent() method, which must be called in the constructor of the code-behind class to initialize the scene graph.

The fx:subclass attribute can only be set on the root element.

FXML files without code-behind class

If the fx:subclass attribute is omitted in an FXML file, it is compiled down to a standalone class with the same name. For example, the document com/sample/MyControl.fxml will yield the class com.sample.MyControl. This is a supported scenario for FXML documents that don’t require a code-behind class with custom code.

Usage

com/sample/MyControl.fxml

<BorderPane xmlns="http://javafx.com/javafx" xmlns:fx="http://jfxcore.org/fxml/2.0"
            fx:subclass="com.sample.MyControl">
</BorderPane>

com/sample/MyControl.java

public class MyControl extends MyControlBase {
    public MyControl() {
        // Code before initialization
        initializeComponent();
        // Code after initialization
    }
}