JavaFX: Custom Equals Method Causes No Refresh in TableView

Question

Here's the situation: I have an ObservableSet (because the ID field for my data must be unique) that has a listener. That listener updates an ObservableList. That ObservableList is, in turn, listened to by a TableView. (According to the comments, this is all necessary because ObservableSet can't be used to back a TableView in JavaFX.)

What we're finding, however, is that doing multiple add operations to the Set don't trigger the refresh of the TableView.

This works fine for:

• Initial list population
• Duplicate set entries (the listener isn't triggered, that's the intended behavior)

However, editing the value, the TableView will only trigger if there's a single add statement (in the example below, commenting out markStructure.add(new MarkStructureItem(2, 15)); makes it work fine, but then you only have a single value). If there's more than one, the TableView doesn't refresh.

This can be worked around by adding a manual refresh at the end of the Listener class (tblTable.refresh()). This is actually how it's functioned up until now, but development now requires the removal of that.

Any idea what's going on? Why is the listener on the TableView not getting triggered for subsequent adds? The data IS being put into the Set and List, that much has been determined; it's just not triggering a refresh.

Code example (not production, but a POC I put together to test and get answers):

public class TestController implements Initializable {
ObservableSet<MarkStructureItem> markStructure = FXCollections.observableSet();
ObservableList<MarkStructureItem> listMarkStructure = FXCollections.observableArrayList();

@FXML
private Pane root;

@FXML
private TableView<MarkStructureItem> tblTable;

@FXML
private TableColumn<MarkStructureItem, Integer> col1;

@FXML
private TableColumn<MarkStructureItem, Integer> col2;

@FXML
private Button btnButton;

private void resetAll() {
    markStructure.clear();
    markStructure.add(new MarkStructureItem(1, 25));
    markStructure.add(new MarkStructureItem(2, 15));
}

@FXML
private void handleButtonAction(ActionEvent event) throws IOException {
    Object source = event.getSource();
    Button btnSource = (Button) source;
    Stage stage = (Stage) root.getScene().getWindow();

    switch (btnSource.getId()) {
        case "btnButton": {
            resetAll();
            break;
        }
    }
}

class MarksUpdater<MarkStructureItem extends configurationeditor.MarkStructureItem> implements SetChangeListener {
    @Override
    public void onChanged(Change change) {
        if (change.wasRemoved()) {
            listMarkStructure.remove(change.getElementRemoved());
        } else if (change.wasAdded()) {
            MarkStructureItem newMarks = (MarkStructureItem) change.getElementAdded();
            listMarkStructure.add(newMarks);
        }
    }
}

@Override
public void initialize(URL url, ResourceBundle rb) {
    markStructure.addListener(new MarksUpdater<MarkStructureItem>());

    col1.setCellValueFactory(
            new PropertyValueFactory<MarkStructureItem, Integer>("id")
    );
    col2.setCellValueFactory(
            new PropertyValueFactory<MarkStructureItem, Integer>("marks")
    );
    col2.setCellFactory(TextFieldTableCell.forTableColumn(new IntegerStringConverter()));
    col2.setOnEditCommit(
            new EventHandler<CellEditEvent<MarkStructureItem, Integer>>() {
                @Override
                public void handle(CellEditEvent<MarkStructureItem, Integer> t) {
                    ((MarkStructureItem) t.getTableView().getItems().get(
                            t.getTablePosition().getRow())
                    ).setMarks(t.getNewValue());
                }
            }
    );
    tblTable.setItems(listMarkStructure);

    resetAll();
}
}

markStructure class:

public class MarkStructureItem {
final SimpleIntegerProperty marks;
final SimpleIntegerProperty id;

@Override
public int hashCode() {
    return this.getId().hashCode();
}

@Override
public boolean equals(Object obj) {
    if (obj.getClass() == this.getClass()) {
        MarkStructureItem thisObj = (MarkStructureItem) obj;
        return thisObj.getId() == this.getId();
    }
    return false;
}

public MarkStructureItem(Integer finishPosition, Integer marks) {
    this.marks = new SimpleIntegerProperty(marks);
    this.id = new SimpleIntegerProperty(finishPosition);
}

public Integer getId() {
    return id.get();
}

public void setMarks(Integer value) {
    marks.set(value);
}

public Integer getMarks() {
    return marks.get();
}

public void setId(Integer value) {
    id.set(value);
}
}

Answer 1

Issue 1:

Your equals implementation is not null-safe and you're comparing the Integers using reference equality (==) instead of equals. This will probably work as long as you're inside the range of cached values and use autoboxing, but cease to work outside that range (this range is only guarantied to be -128 to 127, see Integer.valueOf(int)).
Since you're using the Object in a Set, I recommend making the id unmodifiable anyways. Otherwise you need to remove the value from the set before modifying it and adding it back to the Set (the hash code changes), which would mess up the order in the list unless you temporarily prevent the SetChangeListener from updating the list.
Also using a primitive type will prevent issues with ==.

Issue 2:

For any changes in the marks property to be visible in the TableView, you need to provide a marksProperty() method returning the property itself. This is necessary for the TableView to listen to changes of the property.

public class MarkStructureItem {

    final SimpleIntegerProperty marks;
    final int id;

    @Override
    public int hashCode() {
        return id;
    }

    @Override
    public boolean equals(Object obj) {
        return obj != null
                  && obj.getClass() == this.getClass()
                  && this.id == ((MarkStructureItem) obj).id; // primitive type can be compared using ==
                  // && this.getId().equals(((MarkStructureItem) obj).getId()); // alternative for non-primitive types
    }

    public MarkStructureItem(int finishPosition, Integer marks) {
        this.marks = new SimpleIntegerProperty(marks);
        this.id = finishPosition;
    }

    public int getId() {
        return id;
    }

    public IntegerProperty marksProperty() {
        return marks;
    }