javafx.fxml.LoadException: fx:controller can only be applied to root element.

<AnchorPane fx:id="root" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="320.0" prefWidth="480.0" style="-fx-background-color: lightblue" xmlns:fx="http://javafx.com/fxml" fx:controller="com.th.officesuite.ui.login.LoginController">
....
</AnchorPane>

public FxmlDialog(final DialogController controller, URL fxml, Window owner, StageStyle style, LanguageModel lang) {
    super(style);
    initOwner(owner);
    initModality(Modality.WINDOW_MODAL);
    FXMLLoader loader = new FXMLLoader();
    try {
        loader.setControllerFactory(new Callback<Class<?>, Object>() {
            @Override
            public Object call(Class<?> aClass) {
                return controller;
            }
        });
        loader.setBuilderFactory(new JavaFXBuilderFactory());
        URL systemResource1 = ClassLoader.getSystemResource("fxml/LoginView.fxml");
        loader.setResources(lang.getBundle());
        loader.setLocation(systemResource1);
        Scene scene = new Scene((Parent) loader.load());
        scene.getRoot().setOnMouseDragged(getMouseDraggedHandler());
        scene.getRoot().setOnMousePressed(getMousePressedHandler());
        setScene(scene);
        fxmlStream.close();
        controller.setDialog(this);
    } catch (IOException e) {
        System.out.println(e.getMessage());
        throw new RuntimeException(e);
    }
}