无法在运行时填充JavaFX ComboBox

Question

I am doing a project where I have to fill a ComboBox with attributes from objects the user has just stored in a Hashmap before. This means I cannot assign the Items to the ComboBox in advance. This is the first time I am trying to use javaFX. So far it was ok, but when I try to fill the ComboBox "loggedOnUsersDropDown", nothing happens. It just stays empty. I created the UI including the ComboBox with scene builder. The code of the method looks like this:

@FXML
protected void loadLoggedOn(){
    ArrayList<String> loggedOn = new ArrayList();

    for (User LOGGED_Onkey : bd.currentSSO.LOGGED_ON.keySet()) {
        loggedOn.add(LOGGED_Onkey.getAttribute(LOGGED_Onkey.USER_NAME));          //System.out.println(LOGGED_Onkey.getAttribute(LOGGED_Onkey.USER_NAME));
    }

    ObservableList<String> obList = FXCollections.observableArrayList(loggedOn);
    //loggedOnUsersDropDown.getItems().clear();
    loggedOnUsersDropDown = new ComboBox<String>();
    loggedOnUsersDropDown.getItems().addAll(obList);
    System.out.println(loggedOn.size());
}

I would appreciate any answer. Thanks in advance and soory if i forgot some important information.

Answer 1

You are creating a new ComboBox and populating it. That ComboBox is not a part of your scene graph, so you don't see the result of populating it.

Assuming the @FXML injection is set up correctly, you should be able to just remove the line

loggedOnUsersDropDown = new ComboBox<String>();

and it will work correctly.