JavaFX TableView. How to check that user input uniqe value

Question

I have the following problem: I write my app using JavaFX. I use TableView. Users should use it to observe, add and remove data. I have ID field that should be unique. So when user finishes to edit it I have to check whether result is unique or not. And if it’s unique I have to dismiss changings. Or even better I have to check it at the moment when data is updated and if necessary skip update.

I have TableView with three columns

    colID.setCellValueFactory((TableColumn.CellDataFeatures<CDataType, String> cell) -> cell.getValue().getSID());
    colCaption.setCellValueFactory((TableColumn.CellDataFeatures<CDataType, String> cell) -> cell.getValue().getSCaption());
    colType.setCellValueFactory((TableColumn.CellDataFeatures<CDataType, String> cell) -> cell.getValue().getSType());

    colID.setCellFactory(TextFieldTableCell.forTableColumn());
    colCaption.setCellFactory(TextFieldTableCell.forTableColumn());
    colType.setCellFactory(TextFieldTableCell.forTableColumn());

    lstObservable = FXCollections.observableList(lstData, (CDataType param)->{

        param.getSID().addListener((ObservableValue<? extends String> observable, String oldValue, String newValue) -> {

                System.out.println("getSID().ChangeListener: Changed: " + observable + ")"+ observable.getClass() + ") [" + oldValue + " -> " + newValue + "]");
            }
        });

        return new Observable[]{param.getSID(),
                                param.getSCaption(),
                                param.getSType()
        };
    });

    tabView.setItems(lstObservable);

What is usual practice for this? I’m sure that this problem is not new, but I can not find solution.

UPD: I mean that I don't understand what event should I handle to dimiss user changings. I suppose that it must be ChangeListener but if I change back data item value I got infinite recursion.

well, the most straightforward approach is to collect all ids in a Set and then upon new value inserted check if that set contains that id. If don't have millions of records that would work rather fast — Enigo
The problem is that I don't know where I should check it? If in ChangeListener how can I avoid changings? — Yura

purring pigeon purring pigeon · Accepted Answer · 2017-01-26T14:22:05

You can handle this in the edit commit - something like the following:

colID.setOnEditCommit(event -> {
    String newValue = event.getNewValue();
    if(checkUniqueness(newValue)){
        event.getRowValue().setSID(newValue);
    }else {
        event.getRowValue().setSID(null);
    }

    //Weird FX Bug - on the second time through, the value was set, but the table
    //column didn't repaint, showing the incorrect amount.
    colID.setVisible(false);
    colID.setVisible(true);
});

//Stream the backing collection for the table and look for the value that needs to be unique

public boolean checkUniqueness(String value) {
        return backingCollection
            .stream()
            .noneMatch(item -> item.getSID().equals(value));
    }

JavaFX TableView. How to check that user input uniqe value

1 Answers