Question

I’m running into a weird thingy here. I’m trying to add a JLabel inside a JTable cell. Label icon may change based on some criteria. I created a dummy project following specs from here: http://javanepal.wordpress.com/2010/06/30/adding-jlabel-in-jtable/

And it works fine. I changed the TableModel to extend from AbstractTableModel instead of DefaultTableModel and when adding a row now I get this if I inspect the Object []:

[javax.swing.JLabel[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=,
flags=8388608,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,
disabledIcon=,horizontalAlignment=LEADING,horizontalTextPosition=TRAILING,
iconTextGap=4,labelFor=,text=Row  1,Col1,verticalAlignment=CENTER,
verticalTextPosition=CENTER], whatever....]

The code is this, for the TableModel:

public class MyModel extends javax.swing.table.AbstractTableModel {

    Object[][] row = {{new JLabel("Row 1 Col 1"), "Row 1 Col 2", "Row 1 Col3"},
        {new JLabel("Row 2 Col 1"), "Row 2 Col 2", "Row 2 Col3"},
        {new JLabel("Row 3 Col 1"), "Row 3 Col 2", "Row 3 Col3"},
        {new JLabel("Row 4 Col 1"), "Row 4 Col 2", "Row 4 Col3"}};
    Object[] col = {"Column 1", "Column 2", "Column 3"};
    protected Vector<Object> data;

    public void addRow(Object o[]) {
        for (int i = 0; i < o.length; i++) {
            if (o[i] == null) {
                o[i] = new String();
            }
        }
        data.addElement(o);
        fireTableRowsInserted(data.size() - 1, data.size() - 1);
    }

    public MyModel() {
        super();
        data = new Vector<Object>();
        //Adding rows
        for (Object[] r : row) {
            addRow(r);
        }
    }

    @Override
    public Class getColumnClass(int columnIndex) {
        if (columnIndex == 0) {
            return getValueAt(0, columnIndex).getClass();
        } else {
            return super.getColumnClass(columnIndex);
        }
    }

    @Override
    public int getColumnCount() {
        // TODO Auto-generated method stub
        return 0;
    }

    @Override
    public int getRowCount() {
        // TODO Auto-generated method stub
        return 0;
    }

    @Override
    public Object getValueAt(int arg0, int arg1) {
        // TODO Auto-generated method stub
        return null;
    }
}

Here is the code for the testing class:

public class MyTableTest extends JFrame {

    public MyTableTest(String title) {
        super(title);
        showGUI();
    }

    public void showGUI() {
        JTable table = new JTable();
        table.setModel(new MyModel());//invoking our custom model
        //loadMessages(table);
        table.setDefaultRenderer(JLabel.class, new Renderer());// for the rendering of cell
        JScrollPane jp = new JScrollPane(table);
        getContentPane().add(jp);
        setVisible(true);
        setSize(500, 300);
    }

    public static void main(String[] args) {
        MyTableTest t = new MyTableTest("Table Custom");
    }
}

I’m really confused why this happens, the message is not very clarifying regarding the issue.

Thanks!

Answer 1

You did not post the message, nor what the problem is. But just looking at your code I can already remark a number of issues

1. Why bother storing JLabel instances in your TableModel. If you want to render the contents of your TableModel by using JLabel instances, you can do this in the renderer
2. Your TableModel implementation returns 0 for both the model and row count (see your getColumnCount() and getRowCount() methods)
3. Your getValueAt always returns null, leading to a NullPointerException in your getColumnClass method since you use getValueAt(0, columnIndex).getClass()
4. Please call the contents of your main method on the EDT

Solve these first and see what happens