Java: how to make fireTableStructureChanged change an AbstractTableModel?

Question

I have made a custom AbstractTableModel. The constructor initialises the model with data from a file. However, I wish to add an extra column to the model (this is because of SQL limitations in its columns).

I seek to achieve this by adding to the initialisation code a call to an addColumn(String columnName, Vector columnData) method.

This addColumn method in my custom AbstractTableModel is derived directly from DefaultTableModel's addColumn method, including "fireTableStructureChanged()".

Yet when I run this code, fireTableStructureChanged() appears not to add my new Column and the JTable displays only with data from the file. Why might this be?

Here is a short indication of the code I am using:

public class Dummy extends AbstractTableModel {
    public Dummy() {
        //load data from SQL file into ResultSets
        //transfer ResultSet.metadata into columnHeaders Vector<String>
        //transfer ResultSet.data into columnDatums Vector<String>
        fireTableChanged(null);
        addColumn("Added Heading", (Vector)null);
    }

    public addColumn(String columnHeader, Vector columnData) {
         columnHeaders.add(columnHeader);
         // transfer columnData into columnDatums
         fireTableStructureChanged();
    }
 }

Is it a listener problem - is nothing listening at this point in time to fireTableStructureChanged()?

@kleopatra - thanks but I know them. dummy is no more than a throw-away class name for stackoverflow purposes! — Arvanem, Apr 04 '12 at 09:54
it's hurting the eyes of potential helpers :-) Which can't be what you want ... — kleopatra, Apr 04 '12 at 09:57
@kleopatra: so true! I've amended the code snippet. Lesson appreciated! — Arvanem, Apr 04 '12 at 15:26

score 4 · Accepted Answer · edited May 23 '17 at 10:34

4

You'll have to reveal your implementation of the three required (i.e. unimplemented) methods specified by the TableModel interface in AbstractTableModel. In particular, getColumnCount() and getRowCount() must return the updated values. The fireXxx() methods simply instruct the view to query the model via getValueAt(). The data has to be there waiting for getValueAt() to retrieve. EnvTableTest is a simple example. Also, consider a more modern alternative to Vector, which includes possibly uneeded synchronization code.

edited May 23 '17 at 10:34

Community

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answered Apr 04 '12 at 02:32

trashgod

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+1 for your thoughtful and in depth response. I will review the methods and try to solve the issue in the way you suggest. If it works out I'll accept your answer. If I struggle, I'll append the code to the question. Many thanks – Arvanem Apr 04 '12 at 07:33
you were quite correct. I had to ensure getColumnCount() and getRowCount() returned updated values. Thanks for the great answer and insight. – Arvanem Apr 04 '12 at 15:24
You're welcome; glad it's working. For reference, see also [*When an Abstract Class Implements an Interface*](http://docs.oracle.com/javase/tutorial/java/IandI/abstract.html). – trashgod Apr 04 '12 at 15:34
To all future readers - to avoid ArrayIndexOutOfBounds exceptions in getValueAt(), I also had to adopt DefaultTableModel's "justifyRows()" method and refactor my columnData into a Vector of Vectors of Objects to use justifyRows(). – Arvanem Apr 04 '12 at 15:36

Java: how to make fireTableStructureChanged change an AbstractTableModel?

1 Answers1