Merged Header Above a JTable Header in Java

Question

I would like to put some extra merged cells for grouping reasons on the top of my table header.

I found something similar to this, answered in thislink from this forum, but also what I need exactly seem to be here that is not answered (.NET) link2. So If I am not clear I attach a picture of what I would like to appear.

I have the columns and I need to make appear these super-columns that I have drawn in the picture.

Any help?

Answer 1

try the Groupable Table Header example given here or here

Answer 2

Here's the Perfectly Working Code:

import java.awt.*;
import javax.swing.*;
import javax.swing.table.*;
import javax.swing.event.*;

import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;

import java.util.Enumeration;

import java.io.ObjectOutputStream;
import java.io.ObjectInputStream;
import java.io.IOException;


/**
    Example of a table header that allows cells to span multiple columns.

    Copyright (C) 2001 Christian Kaufhold <[email protected]>

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/** Just a default renderer. To work with TableHeader, the corresponding
    TableHeader must be read from the JTable client property (see code),
    since JTable.getTableHeader() cannot be used.
*/
class DefaultHeaderRenderer
    extends DefaultTableCellRenderer
{
    {
        setBorder(UIManager.getBorder("TableHeader.cellBorder"));
    }

    public void updateUI()
    {
        super.updateUI();

        setHorizontalAlignment(CENTER);

        setBorder(UIManager.getBorder("TableHeader.cellBorder"));
    }


    public Component getTableCellRendererComponent
        (JTable table, Object value, boolean selected, boolean focused,
        int row, int column)
    {
        TableHeader header;

        if (table != null && (header = (TableHeader)table.getClientProperty(TableHeader.KEY)) != null)
        {
            setForeground(header.getForeground());
            setBackground(header.getBackground());

            setFont(header.getFont());

            setComponentOrientation(header.getComponentOrientation());

            setEnabled(header.isEnabled());
        }
        else
        {
            setForeground(UIManager.getColor("TableHeader.foreground"));
            setBackground(UIManager.getColor("TableHeader.background"));

            setFont(UIManager.getFont("TableHeader.font"));

            setComponentOrientation(ComponentOrientation.UNKNOWN);

            setEnabled(true);
        }

        setText(value != null ? value.toString() : "");

        return this;
    }
}

/** An alternative TableHeader that allows header cells to span multiple
    columns. This is just a bare-bones prototype, things to do are:
    - Optimize paint code to paint only concerned columns
    - Area conversion (columnAtPoint, headerRect or similar)
    - getToolTipText(MouseEvent)
    - resizing of columns (which of the columns should be resized?)
    - moving of columns (which cannot be done in real time since JTable
      doesn't know that it has to paint multiple dragged columns.)
    - how to serialize if the renderer isn't serializable?
    - Accessibility

    Note: JTable aggressively installs its JTableHeader in the column header
    view of JScrollPane, even if it is set to 'null'. To avoid confusion,
    override its configureEnclosingScrollPane() method to do nothing, for
    example.

    Typically, a TableHeader is set up like this:

    TableColumnModel columns = ...;

    // columns contains some XTableColumns that have spans set.

    JTable table = new FixedJTable(data, columns); // see above which fix

    table.setTableHeader(null);

    TableHeader header = new TableHeader(table);

    JScrollPane pane = new JScrollPane(table);

    pane.setColumnHeaderView(header);
*/

public class TableHeader
    extends JComponent
{
    /** TableColumn that also has a headerSpan property. */
    public static class XTableColumn
        extends TableColumn
    {
        private int headerSpan;


        public XTableColumn()
        {
            headerSpan = 1;
        }

        /** number of columns that the header cell spans. */
        public final int headerSpan()
        {
            return headerSpan;
        }

        /** set 'headerSpan'. requires newHeaderSpan > 0. During the
            manipulation of TableColumnModels, there may be times where
            a column spans more columns than there are at the right of it.
            This state is only allowed during such modifications. Once they
            are finished, all spans must not be too large. 
            XTableColumns that are hidden by the spans of their predecessors
            are ignored (in the TableHeader, of course not by the JTable).

            Due to the broken notification way of TableColumnModel/Table-
            Column there is no way to notify the header that it must 
            repaint().
            If firePropertyChange were not private, we could send the
            following fake event
            firePropertyChange("width", getWidth(), getWidth());
            which would handle that (only width and preferred width
            changes can reach the header).
            The moral is: don't change spans later, or if, repaint the
            header manually.
        */
        public void setHeaderSpan(int newHeaderSpan)
        {
            headerSpan = newHeaderSpan;   
        }
    }


    private static TableCellRenderer staticDefaultRenderer
        = new DefaultHeaderRenderer();

    /** Under this key, the table header is stored in the JTable, so that
        the renderer can access it. See demo renderer above.
    */
    public static Object KEY = TableHeader.class;

    private JTable table;

    private transient TableColumnModel columns;

    private TableCellRenderer defaultRenderer
        = staticDefaultRenderer;


    private transient Listener listener;


   public TableHeader(JTable table)
    {
        this.table = table;

        table.putClientProperty(KEY, this);

        this.columns = table.getColumnModel();

        this.listener = createListener();

        table.addPropertyChangeListener(listener);

        columns.addColumnModelListener(listener);

        add(new CellRendererPane());

        updateUI();
    }


    public void updateUI()
    {
        LookAndFeel.installColorsAndFont
            (this, "TableHeader.background", "TableHeader.foreground",
            "TableHeader.font");

        LookAndFeel.installBorder(this, "TableHeader.border");

        if (defaultRenderer instanceof JComponent)
            ((JComponent)defaultRenderer).updateUI();

        revalidate(); repaint();
    }


    public final JTable table()
    {
        return table;
    }

    public void setTable(JTable t)
    {
        JTable oldTable = table;
        TableColumnModel oldColumns = columns;

        table.putClientProperty(KEY, null);

        table.removePropertyChangeListener(listener);

        columns.removeColumnModelListener(listener);

        table = t;

        table.putClientProperty(KEY, this);

        columns = t.getColumnModel();

        table.addPropertyChangeListener(listener);

        columns.addColumnModelListener(listener);

        revalidate(); repaint();

        firePropertyChange("table", oldTable, table);
        firePropertyChange("columns", oldColumns, columns);
    }

    public final TableColumnModel columns()
    {
        return columns;
    }

    /** For serialization, the TableCellRenderer is needed to be serializable.
     */
    public void setDefaultRenderer(TableCellRenderer r)
    {
        TableCellRenderer oldRenderer = defaultRenderer;

        defaultRenderer = r;

        revalidate(); repaint();

        firePropertyChange("defaultRenderer", oldRenderer, defaultRenderer);
    }

    public final TableCellRenderer defaultRenderer()
    {
        return defaultRenderer;
    }


    private TableCellRenderer renderer(TableColumn c)
    {
        TableCellRenderer result = c.getHeaderRenderer();

        if (result != null)
            return result;

        return defaultRenderer;
    }


    private Component component(TableCellRenderer r, TableColumn c, int column)
    {
        return r.getTableCellRendererComponent
            (table, c.getHeaderValue(), false, false, -1, column);
    }


    private Dimension size(long innerWidth)
    {
        Insets i = getInsets();

        return new Dimension((int)Math.min(innerWidth + i.left + i.bottom, Integer.MAX_VALUE), innerHeight() + i.top + i.bottom);
    }


    /** Alas, this cannot be cached. */
    private int innerHeight()
    {
        int result = 0;

        int count = columns.getColumnCount();

        for (int j = 0; j < count; )
        {
            TableColumn c = columns.getColumn(j);

            int span;

            if (c instanceof XTableColumn)
                span = ((XTableColumn)c).headerSpan();
            else
                span = 1;

            Component d = component(renderer(c), c, j);

            result = Math.max(result, d.getPreferredSize().height);

            j += span;
        }

        return result;
    }



    public Dimension getMinimumSize()
    {
        if (isMinimumSizeSet())
            return super.getMinimumSize();

        return size(minWidth(columns));
    }

    public Dimension getPreferredSize()
    {
        if (isPreferredSizeSet())
            return super.getPreferredSize();

        return size(preferredWidth(columns));
    }

    public Dimension getMaximumSize()
    {
        if (isMaximumSizeSet())
            return super.getMaximumSize();

        return size(maxWidth(columns));
    }


    public void paintComponent(Graphics g)
    {
        Insets i = getInsets();

        Rectangle clip = g.getClipBounds();

        CellRendererPane pane = (CellRendererPane)getComponent(0);

        Rectangle r = new Rectangle();

        r.x = i.left;
        r.y = i.top;
        r.height = getHeight() - i.top - i.bottom;

        if (r.height <= 0)
            return;


        int count = columns.getColumnCount();

        for (int j = 0; j < count; )
        {
            TableColumn c = columns.getColumn(j);

            r.width = c.getWidth();

            int span;

            if (c instanceof XTableColumn)
            {
                span = ((XTableColumn)c).headerSpan();

                if (j + span > count)
                {
                    System.err.println("column: "+j+" span: "+span+" > "+count);
                    System.err.println("This state of TableColumnModel is forbidden!");
                    span = count - j;
                }

                for (int k = 1; k < span; k++)
                    r.width += columns.getColumn(j + k).getWidth();
            }
            else
            {
                span = 1;
            }

            Component d = component(renderer(c), c, j);

            pane.paintComponent(g, d, this, 
                r.x, r.y, r.width, r.height, true);

            r.x += r.width;

            j += span;
        }

        pane.removeAll();
    }


    private void readObject(ObjectInputStream in)
        throws IOException, ClassNotFoundException
    {
        in.defaultReadObject();

        listener = createListener();

        table.addPropertyChangeListener(listener);

        columns = table.getColumnModel();

        columns.addColumnModelListener(listener);
    }


    protected Object clone()
        throws CloneNotSupportedException
    {
        throw new CloneNotSupportedException();
    }


    private Listener createListener()
    {
        return new Listener();
    }


    private class Listener
        implements TableColumnModelListener, PropertyChangeListener
    {
        public void propertyChange(PropertyChangeEvent e)
        {
            if (e.getPropertyName().equals("columnModel"))
            {
                TableColumnModel oldColumns = columns;

                columns.removeColumnModelListener(this);

                columns = table.getColumnModel();

                columns.addColumnModelListener(this);

                revalidate(); repaint();

                firePropertyChange("columns", oldColumns, columns);
            }
        }


        public void columnAdded(TableColumnModelEvent e)
        {
            revalidate(); repaint();
        }

        public void columnRemoved(TableColumnModelEvent e)
        {
            revalidate(); repaint();
        }

        public void columnSelectionChanged(ListSelectionEvent e)
        {
        }

        public void columnMoved(TableColumnModelEvent e)
        {
            repaint();
        }

        public void columnMarginChanged(ChangeEvent e)
        {
            revalidate(); repaint();
        }
    }  

    /* Utility methods. Copied here from TableColumnModels. */

    public static long minWidth(TableColumnModel columns)
    {
        long result = 0;

        for (Enumeration e = columns.getColumns(); e.hasMoreElements();)
            result += ((TableColumn)e.nextElement()).getMinWidth();

        return result;
    }

    public static long preferredWidth(TableColumnModel columns)
    {
        long result = 0;

        for (Enumeration e = columns.getColumns(); e.hasMoreElements();)
            result += ((TableColumn)e.nextElement()).getPreferredWidth();

        return result;
    }

    public static long maxWidth(TableColumnModel columns)
    {
        long result = 0;

        for (Enumeration e = columns.getColumns(); e.hasMoreElements();)
            result += ((TableColumn)e.nextElement()).getMaxWidth();

        return result;
    }
}


class TableHeaderExample
{
    public static void main(String[] args)
    {
        DefaultTableModel data = new DefaultTableModel(10, 0);

        data.addColumn("ABC");
        data.addColumn("DEF");
        data.addColumn("GHI");
        data.addColumn("JKL");
        data.addColumn("MNO");
        data.addColumn("PQR");

        TableColumnModel columns = new DefaultTableColumnModel();

        TableHeader.XTableColumn abc = new TableHeader.XTableColumn();
        abc.setHeaderValue("ABC");
        abc.setHeaderSpan(2);

        TableColumn ghi = new TableColumn(2);
        ghi.setHeaderValue("GHI");

        TableHeader.XTableColumn jkl = new TableHeader.XTableColumn();
        jkl.setHeaderValue("JKL");
        jkl.setHeaderSpan(3);
        jkl.setModelIndex(3);

        columns.addColumn(abc);
        columns.addColumn(new TableColumn(1));
        columns.addColumn(ghi);
        columns.addColumn(jkl);
        columns.addColumn(new TableColumn(4));
        columns.addColumn(new TableColumn(5));

        JTable table = new JTable(data, columns)
        {
            protected void configureEnclosingScrollPane()
            {
            }
        };

        table.setTableHeader(null);

        TableHeader header = new TableHeader(table);

        header.setForeground(Color.blue);
        header.setFont(header.getFont().deriveFont(18.0f));

        JScrollPane pane = new JScrollPane(table);

        pane.setColumnHeaderView(header);

        JFrame f = new JFrame();

        f.setContentPane(pane);

        f.pack();

        f.setVisible(true);
    }
}