Extra elements in table are always visible, even without underlying data - javafx-2

Question

Here is my problem. I have table with normal text columns and 2 columns with dropdowns and one with checkboxes. This is my callback for cell factory for dropdown columns :
Callback<TableColumn<Person, String>, TableCell<Person, String>> dropdownConditionCellFactory =
new Callback<TableColumn<Person, String>, TableCell<Person, String>>() {
#Override
public TableCell call(TableColumn p) {
Tools.Tables.ComboBoxCell<partCondition> cell = new Tools.Tables.ComboBoxCell<partCondition>(partConditionList)
return cell;
}
};
And class for this cell factory:
public static class ComboBoxCell extends TableCell {
private ComboBox combo;
public ComboBoxCell() {
combo = new ComboBox();
setGraphic(combo);
setContentDisplay(ContentDisplay.GRAPHIC_ONLY);
}
public ComboBoxCell(ObservableList items) {
combo = new ComboBox();
combo.setItems(items);
setGraphic(combo);
setContentDisplay(ContentDisplay.GRAPHIC_ONLY);
combo.getSelectionModel().selectFirst();
}
public T getSelectedItem()
{
return (T) combo.getSelectionModel().getSelectedItem();
}
public void setSelectedItem(T t)
{
combo.getSelectionModel().select(t);
}
}
My problem is that when Table is quite big and there is only 2 rows in it, dropdowns are produced anyway and it looks like this:
Is there a way to produce only as many dropdowns and checkboxes as many items there is in observable list that feeds this table?

Answer 1

While working with cells, please read the Cell API beforehand, to understand how they are handled under the hood. In short the cells are reused in different rows to render different items/records. Each time when the cell is reused its updateItem() method will be called to refresh the item the cell is rendering. Thus you need to override this method and control the graphic in there, instead of in constructor:
private ComboBox combo;
public ComboBoxCell() {
combo = new ComboBox();
}
public ComboBoxCell(ObservableList items) {
combo = new ComboBox();
combo.setItems(items);
}
#Override
public void updateItem(String item, boolean empty) {
super.updateItem(item, empty);
if (empty) {
setText(null);
setGraphic(null);
} else {
combo.getSelectionModel().select(item);
setGraphic(combo);
setContentDisplay(ContentDisplay.GRAPHIC_ONLY);
}
}