Question

i have a JTree, and when u click leafs, it changes the JTable model and displays a new table (much like an email system). the problem arises when i try to select the columns of the new Table model, it always gives -1, no matter what. NOTE that this works perfectly for the 1st JTable model, but after the changed table,

System.out.println(table.getSelectedColumn());

always returns -1.

EDIT: well, i dont know which code snippet to post here to be honest.

    //constructor
    public TreeSection() {
    super();

    //TREE
    top = new DefaultMutableTreeNode("EMAIL");
    createNodes(top);
    //Create a tree that allows one selection at a time.
    tree = new JTree(top);
    tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
    //Listen for when the selection changes.
    tree.addTreeSelectionListener(this);

    //TABLE
    tableModel = new MyTableModel();
    table = new JTable(tableModel);
    table.setPreferredScrollableViewportSize(new Dimension(500, 70));
    table.setFillsViewportHeight(true);
    table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
    selectionModel = table.getSelectionModel();
    selectionModel.addListSelectionListener(this);


    //SCROLL PANE
    treeView = new JScrollPane(tree);
    tableView = new JScrollPane(table);

    //SPLIT PANE
    splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT);
    splitPane.setTopComponent(treeView);
    splitPane.setBottomComponent(tableView);
    splitPane.setDividerLocation(400);
    splitPane.setPreferredSize(new Dimension(200, 700));

    //Add the split pane to this panel.
    panel.add(splitPane,BorderLayout.WEST);
}

/** Required by TreeSelectionListener interface. */
public void valueChanged(TreeSelectionEvent e) {
    DefaultMutableTreeNode node = (DefaultMutableTreeNode)tree.getLastSelectedPathComponent();

    if (node == null) return;

    Object nodeInfo = node.getUserObject();

    if (node.isLeaf()) {
        MailObject mObj = (MailObject)nodeInfo;
        table.removeAll();
        tableModel.setTableData(mObj.tableD);//changes tree model
        table = new JTable(tableModel);

        panel.repaint();
    }
}

public void valueChanged(ListSelectionEvent event) {
    // Get the data model for this table
    //table.changeSelection(table.getSelectedColumn(), table.getSelectedRow(), false, false);
    TableModel model = (TableModel)table.getModel();
    System.out.println(table.getSelectedColumn());
    }

Answer 1

getSelectedColumn returns -1 when there is no column selected.
If you are sure that a column is being selected then perhaps when you are creating the new table you are calling getSelectedColumn on the old table?

Edit after snippet posted:
You’re creating a new JTable which not only doesn’t have the settings (such as FillsViewPortHeight but also doesn’t have the selection model. Try replacing

table = new JTable(tableModel);

in valueChanged with

table.setModel(tableModel);