Highlighting a column header of a JTable

Question

i'm currently building a little JTable, and want to highlight the column header (and row headers - the row-header part is actually working) when a cell is selected to make it easier to find the associated names with this cell. Here is a picture:

I already tried switching out the renderer for the header with this:

table.getTableHeader().setDefaultRenderer(new ColumnHeaderRenderer());

But it's only called when i click on the header and always says isSelected is false.

This is the code i use for the row-names, including the highlight inside the renderer - code is not by me, i just modified it a little:

/*
 *  Use a JTable as a renderer for row numbers of a given main table.
 *  This table must be added to the row header of the scrollpane that
 *  contains the main table.
 */
public class RowNameTable extends JTable
        implements ChangeListener, PropertyChangeListener {

    private JTable main;

    public RowNameTable(JTable table) {
        main = table;
        main.addPropertyChangeListener(this);

        setFocusable(false);
        setAutoCreateColumnsFromModel(false);
        setModel(main.getModel());
        setSelectionModel(main.getSelectionModel());

        TableColumn column = new TableColumn();
        column.setHeaderValue(" ");
        addColumn(column);
        column.setCellRenderer(new RowNameRenderer(main));

        getColumnModel().getColumn(0).setPreferredWidth(table.getColumnModel().getColumn(0).getPreferredWidth());
        setPreferredScrollableViewportSize(getPreferredSize());
    }

    @Override
    public void addNotify() {
        super.addNotify();

        Component c = getParent();

        //  Keep scrolling of the row table in sync with the main table.

        if (c instanceof JViewport) {
            JViewport viewport = (JViewport) c;
            viewport.addChangeListener(this);
        }
    }

    /*
     *  Delegate method to main table
     */
    @Override
    public int getRowCount() {
        return main.getRowCount();
    }

    @Override
    public int getRowHeight(int row) {
        return main.getRowHeight(row);
    }

    /*
     *  This table does not use any data from the main TableModel,
     *  so just return a value based on the row parameter.
     */
    @Override
    public Object getValueAt(int row, int column) {
        return Integer.toString(row + 1);
    }

    /*
     *  Don't edit data in the main TableModel by mistake
     */
    @Override
    public boolean isCellEditable(int row, int column) {
        return false;
    }
//
//  Implement the ChangeListener
//

    public void stateChanged(ChangeEvent e) {
        //  Keep the scrolling of the row table in sync with main table

        JViewport viewport = (JViewport) e.getSource();
        JScrollPane scrollPane = (JScrollPane) viewport.getParent();
        scrollPane.getVerticalScrollBar().setValue(viewport.getViewPosition().y);
    }
//
//  Implement the PropertyChangeListener
//

    public void propertyChange(PropertyChangeEvent e) {
        //  Keep the row table in sync with the main table

        if ("selectionModel".equals(e.getPropertyName())) {
            setSelectionModel(main.getSelectionModel());
        }

        if ("model".equals(e.getPropertyName())) {
            setModel(main.getModel());
        }
    }

    /*
     *  Borrow the renderer from JDK1.4.2 table header
     */
    private static class RowNameRenderer extends DefaultTableCellRenderer {

        private JTable main;

        public RowNameRenderer(JTable main) {
            this.main = main;
            setHorizontalAlignment(JLabel.CENTER);
        }

        @Override
        public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
            if (table != null) {
                JTableHeader header = table.getTableHeader();

                if (header != null) {
                    setForeground(header.getForeground());
                    setBackground(header.getBackground());
                    setFont(header.getFont());
                }
            }

            if (isSelected) {
                setFont(getFont().deriveFont(Font.BOLD));
            }

            setText((value == null) ? "" : main.getColumnName(row));
            setBorder(UIManager.getBorder("TableHeader.cellBorder"));

            return this;
        }
    }
}

And here we have the relevant part to create the table:

    costTableModel = new CostTableModel(costCalc);
    table = new JTable(costTableModel);
    table.setPreferredScrollableViewportSize(table.getPreferredSize());
    table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
    table.setCellSelectionEnabled(true);

    scrollPane = new JScrollPane(table);

    RowNameTable nameTable = new RowNameTable(table);
    scrollPane.setRowHeaderView(nameTable);

And the class costTableModel, just for completeness sake:

public class CostTableModel extends AbstractTableModel {
    private CostCalculator costCalc;

    public CostTableModel(CostCalculator costCalc) {
        this.costCalc = costCalc;
    }

    @Override
    public int getRowCount() {
        return costCalc.getPersonsList().size();
    }

    @Override
    public int getColumnCount() {
        return costCalc.getPersonsList().size();
    }

    @Override
    public String getColumnName(int col) {
        return costCalc.getPersonsList().get(col).getName();
    }

    @Override
    public Object getValueAt(int rowIndex, int columnIndex) {
        Person debtor = costCalc.getPersonsList().get(rowIndex);
        Person debtee = costCalc.getPersonsList().get(columnIndex);

        return costCalc.getAmountOwed(debtor, debtee);
    }

    @Override
    public Class getColumnClass(int c) {
        return getValueAt(0, c).getClass();

    }
}

Thank you for your help in advance!

Answer 1

The basic issue I had was there was no connection between the table header and the selection change. In fact, the header is really clever with it's repaints...

I ended up providing my own header, which attached a listener to the table's selection model and repainted the header on the selection changed.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.EventQueue;
import java.util.List;
import javax.swing.Icon;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.RowSorter;
import javax.swing.RowSorter.SortKey;
import static javax.swing.SortOrder.ASCENDING;
import static javax.swing.SortOrder.DESCENDING;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.JTableHeader;

public class TestColumnHighlight {

    public static void main(String[] args) {
        new TestColumnHighlight();
    }

    public TestColumnHighlight() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JTable table = new JTable();
                DefaultTableModel model = new DefaultTableModel(
                                new Object[]{"abc", "def", "ghi", "jkl"},
                                0);

                model.addRow(new Object[]{0, 0, 0, 0});
                model.addRow(new Object[]{0, 0, 0, 0});
                model.addRow(new Object[]{0, 0, 0, 0});
                model.addRow(new Object[]{0, 0, 0, 0});
                model.addRow(new Object[]{0, 0, 0, 0});

                table.setModel(model);
                table.setTableHeader(new CustomTableHeader(table));
                table.getTableHeader().setDefaultRenderer(new ColumnHeaderRenderer());

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new JScrollPane(table));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class CustomTableHeader extends JTableHeader {

        public CustomTableHeader(JTable table) {
            super();
            setColumnModel(table.getColumnModel());
            table.getColumnModel().getSelectionModel().addListSelectionListener(new ListSelectionListener() {
                @Override
                public void valueChanged(ListSelectionEvent e) {
                    repaint();
                }
            });
        }

        @Override
        public void columnSelectionChanged(ListSelectionEvent e) {
            repaint();
        }

    }

    public class ColumnHeaderRenderer extends DefaultTableHeaderCellRenderer {

        @Override
        public Component getTableCellRendererComponent(JTable table, Object value, boolean selected, boolean focused, int row, int column) {
            super.getTableCellRendererComponent(table, value, selected, focused, row, column);

            int selectedColumn = table.getSelectedColumn();
            System.out.println("Selected " + selectedColumn + "-" + column);
            if (selectedColumn == column) {
                Color bg = table.getSelectionBackground();
                setBackground(bg);
                setOpaque(true);
            } else {
                setOpaque(false);
            }

            return this;
        }

    }

    public class DefaultTableHeaderCellRenderer extends DefaultTableCellRenderer {

        public DefaultTableHeaderCellRenderer() {
            setHorizontalAlignment(CENTER);
            setHorizontalTextPosition(LEFT);
            setVerticalAlignment(BOTTOM);
            setOpaque(false);
        }

        @Override
        public Component getTableCellRendererComponent(JTable table, Object value,
                        boolean isSelected, boolean hasFocus, int row, int column) {
            super.getTableCellRendererComponent(table, value,
                            isSelected, hasFocus, row, column);
            JTableHeader tableHeader = table.getTableHeader();
            if (tableHeader != null) {
                setForeground(tableHeader.getForeground());
            }
            setIcon(getIcon(table, column));
            setBorder(UIManager.getBorder("TableHeader.cellBorder"));
            return this;
        }

        protected Icon getIcon(JTable table, int column) {
            SortKey sortKey = getSortKey(table, column);
            if (sortKey != null && table.convertColumnIndexToView(sortKey.getColumn()) == column) {
                switch (sortKey.getSortOrder()) {
                    case ASCENDING:
                        return UIManager.getIcon("Table.ascendingSortIcon");
                    case DESCENDING:
                        return UIManager.getIcon("Table.descendingSortIcon");
                }
            }
            return null;
        }

        protected SortKey getSortKey(JTable table, int column) {
            RowSorter rowSorter = table.getRowSorter();
            if (rowSorter == null) {
                return null;
            }

            List sortedColumns = rowSorter.getSortKeys();
            if (sortedColumns.size() > 0) {
                return (SortKey) sortedColumns.get(0);
            }
            return null;
        }
    }
}