How to prepare FXML Controller to be GC - javafx

Question

I have an issue in my application. Any Controllers are garbage collected.
I was prepared one, pretty simple with clear function, but it is no removed from memory.
#Log4j2
public class DialogOpenProjectController extends DialogPane implements Initializable, FXMLController, FXMLPane, FXMLDialogController {
#FXML
private ObjectProperty<ResourceBundle> languageBundle = new SimpleObjectProperty<>();
#FXML
private JFXTabPane TAB_PANE_OPEN_PROJECT;
#FXML
private JFXButton BUTTON_CONFIRM;
private Tab tabOpenNewProject;
private Tab tabOpenExistingProject;
private Stage stage;
private ChangeListener<? super ResourceBundle> languageListener = this::languageChange;
private ChangeListener<? super Tab> selectedTabListener = this::selectedTabChanged;
{
tabOpenExistingProject = new Tab();
tabOpenNewProject = new Tab();
}
/**
* Initializes the controller class.
*/
#Override
public void initialize(URL url, ResourceBundle rb) {
log.trace(LogMessages.MSG_CTRL_INITIALIZATION);
this.languageBundle.setValue(rb);
initTabs();
addSelectedTabListener();
addDisableButtonListener();
addLanguageListener();
log.trace(LogMessages.MSG_CTRL_INITIALIZED);
}
#FXML
public void cancel() {
this.stage.close();
clean();
}
#FXML
public void confirm() {
if (TAB_PANE_OPEN_PROJECT.getSelectionModel().getSelectedItem().equals(tabOpenNewProject)) {
actionNewProject();
} else if (TAB_PANE_OPEN_PROJECT.getSelectionModel().getSelectedItem().equals(tabOpenExistingProject)) {
actionOpenProject();
} else {
//To to show error
}
this.stage.close();
clean();
}
private void initTabs() {
TAB_PANE_OPEN_PROJECT.getSelectionModel().select(tabOpenNewProject);
}
private void addSelectedTabListener() {
TAB_PANE_OPEN_PROJECT.getSelectionModel().selectedItemProperty().addListener(selectedTabListener);
}
private void addDisableButtonListener() {
//nothing to do temporary
}
private void clean() {
this.languageBundle.removeListener(languageListener);
languageBundle.unbind();
languageBundle.setValue(null);
TAB_PANE_OPEN_PROJECT.getSelectionModel().selectedItemProperty().removeListener(selectedTabListener);
TAB_PANE_OPEN_PROJECT.getSelectionModel().clearSelection();
TAB_PANE_OPEN_PROJECT.getTabs().clear();
BUTTON_CONFIRM.disableProperty().unbind();
selectedTabListener = null;
languageListener = null;
tabOpenNewProject = null;
tabOpenExistingProject = null;
stage = null;
getChildren().clear();
}
private void addLanguageListener() {
this.languageBundle.addListener(languageListener);
}
private void languageChange(ObservableValue<? extends ResourceBundle> observable, ResourceBundle oldValue, ResourceBundle newValue) {
reloadElements();
}
private String getValueFromKey(String key) {
return this.languageBundle.getValue().getString(key);
}
private void reloadElements() {
// Nothing to do
}
public void setStage(Stage stage) {
this.stage = stage;
}
private void selectedTabChanged(ObservableValue<? extends Tab> observable, Tab oldValue, Tab newValue) {
if (newValue.equals(tabOpenNewProject)) {
BUTTON_CONFIRM.setText(getValueFromKey(Keys.CREATE));
} else if (newValue.equals(tabOpenExistingProject)) {
BUTTON_CONFIRM.setText(getValueFromKey(Keys.OPEN));
}
}
}
For loading FXML files I use Singleton Class ScreenManager. This method is called to load this Dialog :
public void showNewDialog( FilesFXML fxml) {
FXMLLoader loader = new FXMLLoader(getClass().getResource(fxml.toString()), context.getBundleValue());
try {
Stage dialogStage = new Stage();
AnchorPane dialogwindow = (AnchorPane) loader.load();
FXMLDialogController controller = loader.getController();
dialogStage.initModality(Modality.WINDOW_MODAL);
dialogStage.initOwner(this.getStage());
Scene scene = new Scene(dialogwindow);
dialogStage.setScene(scene);
dialogStage.setResizable(false);
controller.setStage(dialogStage);
dialogStage.showAndWait();
} catch (Exception ex) {
log.error(ex.getMessage());
log.error(ex.getCause());
ex.printStackTrace();
}
}
I was checked it in VisualVM and I see one 1 of this controller and 2 lambdas ( I suppose it consiste initialization of 2 listener)
But event clear function is called this dialog is still in memory and cannot be garbage collected. I have no more idea how to force removing it. It is reallegrave, because it consist all of my Controllers.

Answer 1

I'm pretty confused what you are asking and what you are talking about. Nevertheless, if that dialog window is open, there is no way it can be garbage collected.
The JavaFX main API is holding a strong reference of the stage (maybe the scene too).
The stage/scene is holding strong reference of all the nodes specified in your FXML file.
Some of those nodes are holding strong reference of the controller because you have specified action event handlers in the controller.
In order to make the controller eligible for garbage collection, you need to break this chain somewhere.
The easiest way is to close the dialog window. When the window is closed, because the JavaFX engine does not need to manage render pulses anymore, it will release its reference to the stage. At that point, the whole thing under that stage is eligible for garbage collection, if nothing else (that itself is not eligible for garbage collection) is holding strong references of them.