Cannot force JavaFX TableView to refresh from another Window/Controller

Question

I have two windows and two controllers.

In the first window is a button which opens a second window and TableView. The second window is a form where I insert properties of my class. After inserting I click on "Save" and add new created object to a static list. This should be shown in a TableView. When I use only one window and one controller everything works fine but splitting the functionality as described in two windows the TableView is not refreshed.

Here is my minimal example:

MAIN CONTROLLER

public class Controller {

    @FXML
    public TableView tableView;

    @FXML
    private Button openWindow;


    // called by the FXML loader after the labels declared above are injected:
    public void initialize() {

        TableColumn mailColumn = new TableColumn("E-Mail");
        tableView.getColumns().addAll(mailColumn);
        mailColumn.setCellValueFactory(new PropertyValueFactory<Person,String>("mail"));


        openWindow.setOnAction((event) -> {
            new PersonInputForm(event);
        });


    }

    // ######   Receiver TableView Action Handling #######
    public void updateReceiverList(){
        final ObservableList<Person> data = FXCollections.observableArrayList(Memory.receiverList);
        tableView.getItems().clear();
        tableView.getItems().addAll(data);
    }

}

SECONDARY CONTROLLER

public class PersonInputFormController {


    @FXML
    private TextField mail;

    @FXML
    private AnchorPane personInputFormAnchorPane;

    private Controller mainController ;
    Stage stage;

    public void setStage() {
        stage = (Stage) personInputFormAnchorPane.getScene().getWindow();
    }

    public void setMainController(Controller mainController){
        this.mainController = mainController;
    }

    public void save(){
        Memory.saveReceiver(mail);
        mainController.updateReceiverList();
        stage.close();
    }


}

MAIN WINDOW

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{

        FXMLLoader loader = new FXMLLoader(getClass().getResource("sample.fxml"));
        Parent root = loader.load();
        Scene scene = new Scene(root);
        primaryStage.setScene(scene);
        primaryStage.setResizable(false);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

SECONDARY WINDOW

public class PersonInputForm {

    public PersonInputForm(ActionEvent event) {

        Stage stage = new Stage();

        FXMLLoader mainFxmlLoader = new FXMLLoader(getClass().getResource("../sample.fxml"));
        try {
            mainFxmlLoader.load();
        } catch (IOException e) {
            e.printStackTrace();
        }
        Controller mainController = mainFxmlLoader.getController();


        FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("PersonInputForm.fxml"));
        Parent root = null;
        try {
            root = (Parent)fxmlLoader.load();
        } catch (IOException e) {
            e.printStackTrace();
        }

        stage.setScene(new Scene(root));
        stage.initOwner(
                ((Node) (event.getSource())).getScene().getWindow() );

        PersonInputFormController controller = fxmlLoader.<PersonInputFormController>getController();
        controller.setStage();
        controller.setMainController(mainController);

        stage.show();

    }
}

MEMORY

public class Memory {

    public static sample.Person sender = new sample.Person();
    public static ArrayList<sample.Person> receiverList = new ArrayList();

    static public void saveReceiver(TextField mail){
        Person receiver = new Person();
        receiver.setMail(mail.getText());
        receiverList.add(receiver);
    }

}

OBJECT

public class Person {

    private SimpleStringProperty mail = new SimpleStringProperty();

    public String getMail() {
        return mail.get();
    }

    public SimpleStringProperty mailProperty() {
        return mail;
    }

    public void setMail(String mail) {
        this.mail.set(mail);
    }

}

I found the following similar sounding topics:

How to set items of a TableView in a different controller class in JavaFX?

Javafx Update a tableview from another FXML

But, I still don't understand how my problem can be solved.

Thanks in advance!

Answer 1

In your PersonInputForm class' constructor you create an FXMLLoader to load sample.fxml. You then give the controller resulting from this load—a Controller instance—to your PersonInputFormController instance you generate later on. The problem with this is the Controller instance that invoked new PersonInputForm(event) is not the same instance you give to the PersonInputFormController. Remember, each time you call FXMLLoader.load you create a new scene graph connected to a new controller instance.

As you are calling new PersonInputForm(event) from within an instance of Controller, and it's this instance of Controller you need to call updateReceiverList() on, the easiest fix is to pass this to PersonInputForm as well. Then remove the code responsible for loading sample.fxml.

public PersonInputForm(ActionEvent event, Controller mainController) {
    // code...
    controller.setMainController(mainController);
}

Note: It feels wrong to have all this behavior in a constructor.

While the above will solve your problem (I believe), having to clear-and-replace the items of a TableView is not the ideal approach. Take a look at updateReceiverList():

public void updateReceiverList(){
    // Copies Memory.receiverList into new ObservableList
    final ObservableList<Person> data = FXCollections.observableArrayList(Memory.receiverList);
    tableView.getItems().clear();
    // Copies data into the TableView's items list
    tableView.getItems().addAll(data);
}

That code copies a collection into another collection twice. This can become quite expensive when you have a large number of elements. It would be better if you had an observable model that your different controllers could observe and react to.

For instance, you're using an ArrayList to store/share your Persons where you could be using an ObservableList. You could then use tableView.setItems(Memory.receiverList) and any updates your PersonInputFormController makes to the receiverList will be automatically seen by the TableView. As you don't appear to be using multi-threading, this setup shouldn't cause any problems. When, or if, you start utilizing background threads, remember that you must never update the UI—directly or indirectly—from a background thread.

However, using global state (i.e. public static variables) is not ideal either. I recommend reading up on different application architectures such as: Model-View-Controller (MVC), Model-View-Presenter (MVP), Model-View-ViewModel (MVVP), etc. Then try to apply one of them to your application as appropriate.

---

Some links:

• Applying MVC With JavaFx
• Passing Parameters JavaFX FXML

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I'd like to point out one more thing about your code. You're using a lot of raw types. Don't use raw types. For instance, you should have:

@FXML private TableView<Person> tableView;

And:

TableColumn<Person, String> mailColumn = new TableColumn<>("E-Mail");
// which lets you use the diamond operator here
mailColumn.setCellValueFactory(new PropertyValueFactory<>("mail"));

And:

// You're missing the <> on the right hand side
public static ArrayList<Person> receiverList = new ArrayList<>();