JavaFX 8: Automatically numbering TableView rows

Question

I'm trying to automatically include numbers on my table view.

I have 2 tables having a similar structure and the idea is to copy selected items from tableA to tableB on button click.

Total columns: 3
RowCol = supposed to show numbers automatically
TestCol = Test Name (coming from a Model class)
ModCol = Module (coming from a Model class)

I came across this question to solve auto-numbering for tableA.
auto numbered table rows (javafx)

Code:

tableARowCol.setCellValueFactory(cellData -> new ReadOnlyObjectWrapper<Number>(
            tableA.getItems().indexOf(cellData.getValue()) + 1));
tableATestCol.setCellValueFactory(cellData -> cellData.getValue().testCaseNameProperty());
tableAModCol.setCellValueFactory(cellData -> cellData.getValue().moduleNameProperty());

This is working well for tableA and I use the same code for tableB but I get the following problem (The auto numbering is not updating properly when adding data on btn click):

In the image, the row numbers of tableB are showing as 1,2,3,3,3,2,7.
This was the output when I did the following:

• added row 1 from tableA
• added row 2 from tableA
• added row 3 from tableA 3x
• added row 2 from tableA again
• added row 10 from tableA

I want to know what seems to be the problem and how can I fix it. To be honest I do not fully understand the line for auto numbering rows.

Flow of what is happening so far:

• select items from tableA
• add to B by clicking the button add [>>]
• added items are added to an observable list (model) and saved to an XML file

Worth mentioning:

• I have another listener to load the items from XML and populate them to table B. When the items are 'loaded' from XML, the numbering is correct. This is the same data loaded from the XML this time. Notice tableB numberings are correct.

Code for tableB row numbering:

tableBRowCol.setCellValueFactory(cellData -> new ReadOnlyObjectWrapper<Number>(
            tableB.getItems().indexOf(cellData.getValue()) + 1));
tableBTestCol.setCellValueFactory(cellData -> cellData.getValue().testCaseNameProperty());
tableBModCol.setCellValueFactory(cellData -> cellData.getValue().moduleNameProperty());

Thanks in advance for the help!

Answer 1

The problem is that you're using the items list from tableA to determine the indices in tableB.

But:

DON'T USE THAT APPROACH!

I know many users upvoted the answer you used, but it has some serious issues. If there are multiple items in the items list that are equal or even (as in your case) identical, the index will always be the first one found in the List.

Instead use the index property that TableCell provides, which will also get rid of the inefficient search for the item in the list which has a worst case running time of O(n) where n is the size of the items list...

The following is a small variation on @jewelsea's answer:

public class NumberTableCellFactory<S, T> implements Callback<TableColumn<S, T>, TableCell<S, T>> {

    private final int startNumber;

    public NumberTableCellFactory(@NamedArg("startNumber") int startNumber) {
        this.startNumber = startNumber;
    }

    public NumberTableCellFactory() {
        this(1);
    }

    public static class NumberTableCell<S, T> extends TableCell<S, T> {

        private final int startNumber;

        public NumberTableCell(int startNumber) {
            this.startNumber = startNumber;
        }



        @Override
        public void updateItem(T item, boolean empty) {
            super.updateItem(item, empty);

            setText(empty ? "" : Integer.toString(startNumber + getIndex()));
        }

    }

    @Override
    public TableCell<S, T> call(TableColumn<S, T> param) {
        return new NumberTableCell<>(startNumber);
    }

    public static <T> TableColumn<T, Void> createNumberColumn(String text, int startNumber) {
        TableColumn<T, Void> column = new TableColumn<>(text);
        column.setSortable(false);
        column.setEditable(false);
        column.setCellFactory(new NumberTableCellFactory<>(startNumber));
        return column;
    }

}

This can be used like this:

tableA.getColumns().add(NumberTableCellFactory.createNumberColumn("#", 1));
tableB.getColumns().add(NumberTableCellFactory.createNumberColumn("#", 1));