JavaFX - Update a text field through observer pattern - javafx

Question

I am trying to update a text field through observer pattern. The update function in the observer (FXML controller) is called after clicking on a listItem in another controller class. And that works fine. The only problem is that my textfield won't update.
Here is my update function in the observer.
#Override
public void update(Observable o, final Object arg) {
System.out.println("test"); // works
firstNameTextField.setText("test"); // doesn't work (text field is still empty)
System.out.println(firstNameTextField.getText()); //works and shows me the word "test" on my console
}
The funny thing is, if I print the text from the text field on my console it's printing the word "test" on the console. It seems like the text field value is updated but it doesn't show up on the ui.
EDIT:
This is my MainController
public class MainController extends Observable implements Initializable {
private ObservableList<String> items = FXCollections.observableArrayList("item1", "item2");
private List<UserProfile> userProfiles = new ArrayList<UserProfile>();
private String[] tabTitles = { "Profile"};
#FXML
private TabPane tabPane;
#FXML
ListView<String> listView;
#Override
public void initialize(URL arg0, ResourceBundle arg1) {
for (String tabTitle : tabTitles) {
Tab tab = new Tab(tabTitle);
tab.setClosable(false);
tabPane.getTabs().add(tab);
}
tabPane.getSelectionModel().clearSelection();
for (Tab tab : tabPane.getTabs()) {
try {
String newStringValue = tab.getText();
Parent root = FXMLLoader.load(getClass().getResource("profile.fxml"));
tab.setContent(root);
FXMLLoader fxmlLoader = new FXMLLoader();
Object p = fxmlLoader.load(getClass().getResource("profile.fxml").openStream());
if (fxmlLoader.getController() instanceof ProfileController) {
ProfileController profileController = (ProfileController) fxmlLoader.getController();
this.addObserver(profileController);
}
} catch (IOException e) {
e.printStackTrace();
}
}
tabPane.getSelectionModel().selectFirst();
listView.setItems(items);
listView.getSelectionModel().selectedItemProperty().addListener(new ChangeListener<String>() {
#Override
public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
setChanged();
notifyObservers();
}
});
}
}
ProfileController
public class ProfileController implements Initializable, Observer {
#FXML
TextField firstNameTextField;
#Override
public void initialize(URL arg0, ResourceBundle arg1) {
}
#Override
public void update(Observable o, final Object arg) {
System.out.println("test"); // works
firstNameTextField.setText("test"); // doesn't work (text field is still empty)
System.out.println(firstNameTextField.getText()); //works and shows me the word "test" on my console
}
}
Can anybody help me out with this?
Thanks!

Answer 1

When you execute
Object p = fxmlLoader.load(getClass().getResource("profile.fxml").openStream());
if (fxmlLoader.getController() instanceof ProfileController) {
ProfileController profileController = (ProfileController) fxmlLoader.getController();
this.addObserver(profileController);
}
you load the structure represented by profile.fxml, and place that hierarchy (including firstNameTextField) in the object you called p. When you invoke update(...) on profileController, it changes the text in the text field that is part of the hierarchy of p. However, you never do anything with p: you don't display it in your UI. So when you change the text of the text field, the changes are of course invisible (because you are changing a text field that isn't displayed).
Presumably, since you said you have the text field displayed, somewhere in the code you couldn't be bothered to include you are loading profile.fxml and displaying the content in the UI. You need to get the reference to that controller, and register it as an observer. Registering an arbitrary instance of the same class will not have the desired effect.