I have a JScrollpane that contains a JTable. The code below
demonstrates my resizing problem: when the button is pressed the
TableModel is changed and the scrollpane is repainted but its size does
not change. After pressing the button, if I resize the owner JFrame
then the scrollpane is redrawn the correct size.

I've overriden the getPreferredSize method of the JScrollpane to track
the size of the JTable. How can I force the scrollpane to be resized
when I change the TableModel?

Thanks for any advice.

Rick

import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Enumeration;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableColumn;

public class FrmTasksList extends javax.swing.JFrame implements
ActionListener {

    private JButton                    btnManageTask = null;
    private JPanel                     myContentPane = null;
    private JScrollPane                scrTasks = null;
    private JTable                     tblTasks = null;
    private DefaultTableModel        taskTableModel;
    public static int                 DEFAULT_COLUMN_WIDTH  = 20;

public FrmTasksList(String title) {
    super(title);

    setContentPane(getmyContentPane());
}

public void actionPerformed(ActionEvent ae){

    if (ae.getSource() == getBtnManageTask()) {
        tblTasks.setModel(getTaskTableModel(7,7));
        setupColumns(gettblTasks())    ;
        scrTasks.revalidate();
    }
}

/**
* Return the myContentPane property value.
* @return javax.swing.JPanel
*/

private javax.swing.JPanel getmyContentPane() {
    if (myContentPane == null) {

        myContentPane = new javax.swing.JPanel();
        myContentPane.setName("myContentPane");
        myContentPane.setLayout(new java.awt.GridBagLayout());

        java.awt.GridBagConstraints gbcScrTasks = new
java.awt.GridBagConstraints();
        gbcScrTasks.gridx = 0; gbcScrTasks.gridy = 1;
        gbcScrTasks.fill = java.awt.GridBagConstraints.NONE;
        gbcScrTasks.anchor = GridBagConstraints.WEST;
        gbcScrTasks.weightx = 1.0;
        gbcScrTasks.weighty = 0.0;
        gbcScrTasks.insets = new java.awt.Insets(0, 10, 10, 10);
        myContentPane.add(getScrTasks(), gbcScrTasks);

        java.awt.GridBagConstraints gbcButton = new
java.awt.GridBagConstraints();
        gbcButton.gridx = 0; gbcButton.gridy = 5;
        gbcButton.fill = java.awt.GridBagConstraints.NONE;
        gbcButton.insets = new java.awt.Insets(0, 10, 10, 10);
        myContentPane.add(getBtnManageTask(), gbcButton);

    }
    return myContentPane;
}
/**
* Return the scrTasks property value.
* @return javax.swing.JScrollPane
*/

private javax.swing.JScrollPane getScrTasks() {
    if (scrTasks == null) {
        scrTasks = new javax.swing.JScrollPane(){
            public Dimension getPreferredSize(){
                return gettblTasks().getPreferredSize() ;

            }
        };
        scrTasks.setViewportView(gettblTasks());
        scrTasks.setVerticalScrollBarPolicy(javax.swing.JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
        scrTasks.setHorizontalScrollBarPolicy(javax.swing.JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);

    }
    return scrTasks;
}
/**
* Return the tblTasks property value.
* @return javax.swing.JTable
*/

private JTable gettblTasks() {
    if (tblTasks == null) {

            tblTasks = new JTable(getTaskTableModel(4,4));
            tblTasks.getTableHeader().setEnabled(false);
            tblTasks.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
            tblTasks.setRowHeight(20);
            tblTasks.setAutoCreateColumnsFromModel(true);
            setupColumns(tblTasks);

    }
    return tblTasks;
}
public void setupColumns(JTable table) {

    table.tableChanged(null);

    Enumeration enum =
table.getTableHeader().getColumnModel().getColumns();
    while (enum.hasMoreElements()) {
        TableColumn column = (TableColumn)enum.nextElement();
            //set column widths
        int width = DEFAULT_COLUMN_WIDTH;
        column.setMinWidth(width);
        column.setMaxWidth(width);
        column.setPreferredWidth(width);
        column.setResizable(false);

    }

}

/**
* main entrypoint - starts the part when it is run as an application
* @param args java.lang.String[]
*/
public static void main(java.lang.String[] args) {

        FrmTasksList aFrmTasksList;
        aFrmTasksList = new FrmTasksList("Test resizing JScrollpane");

        aFrmTasksList.setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);
        aFrmTasksList.setSize(700, 700);

    //    aFrmTasksList.pack();
        aFrmTasksList.setVisible(true);

}

    public JButton getBtnManageTask() {
        if (btnManageTask == null) {
            btnManageTask = new JButton();
            btnManageTask.setText("Enlarge Table");
            btnManageTask.addActionListener(this);
        }

        return btnManageTask;
    }

    protected DefaultTableModel getTaskTableModel(int numberOfRows, int
numberOfColumns) {

        taskTableModel = new DefaultTableModel(numberOfRows,numberOfColumns);
   
        return taskTableModel;
       
    }
}