Center text alignment in JTable cell with TextAreaRenderer

Question

I am using a TextAreaRenderer to word-wrap text within my JTable cells. However, specifications for my project call for the ability to center the text (both horizontally and vertically). I cannot figure out how to do this.

Because I am already using a TextAreaRenderer which extends JTextArea, I am unable to extend DefaultTableCellRenderer which is necessary to access the setHorizontalAlignment() and setVerticalAlignment() methods (see this question and answer: How to center in JTable cell a value?). I can't implement DefaultTableCellRenderer because it is not an interface.

SSCCE with the TextAreaRenderer I am using:

import java.awt.Component;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextArea;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableCellRenderer;
import javax.swing.table.TableColumn;
import javax.swing.table.TableColumnModel;

public class Test {

    public static void main(String args[]) {
        JFrame frame = new JFrame();
        JTable table = new JTable();
        JScrollPane jsp = new JScrollPane(table);
        Object[][] data = new Object[2][2];
        data[0][0] = 1;
        data[0][1] = "Super long text just to illustrate word wrap. Super long text just to illustrate word wrap. Super long text just to illustrate word wrap. Super long text just to illustrate word wrap. Super long text just to illustrate word wrap. Super long text just to illustrate word wrap. Super long text just to illustrate word wrap. Super long text just to illustrate word wrap. ";
        data[1][0] = 2;
        data[1][1] = "Two Lines / Two Lines";
        String[] headers = new String[]{"Digit", "Text"};
        table.setModel(new DefaultTableModel(data, headers) {

            @Override
            public Class<?> getColumnClass(int columnIndex) {
                switch(columnIndex){
                    case 1: return Integer.class;
                    case 2: return String.class;
                    default: return Object.class;
                }
            }
        });
        table.getColumnModel().getColumn(1).setCellRenderer(new TextAreaRenderer());
        frame.add(jsp);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }



    static class TextAreaRenderer extends JTextArea implements TableCellRenderer {

        private final DefaultTableCellRenderer adaptee = new DefaultTableCellRenderer();
        /** map from table to map of rows to map of column heights */
        private final Map cellSizes = new HashMap();


        public TextAreaRenderer() {
            setLineWrap(true);
            setWrapStyleWord(true);
        }

        public Component getTableCellRendererComponent(
                JTable table, Object obj, boolean isSelected,
                boolean hasFocus, int row, int column) {

            // set the colours, etc. using the standard for that platform
            adaptee.getTableCellRendererComponent(table, obj,
                    isSelected, hasFocus, row, column);
            setForeground(adaptee.getForeground());
            setBackground(adaptee.getBackground());
            setBorder(adaptee.getBorder());
            setFont(adaptee.getFont());
            setText(adaptee.getText());


            // This line was very important to get it working with JDK1.4
            TableColumnModel columnModel = table.getColumnModel();
            setSize(columnModel.getColumn(column).getWidth(), 100000);
            int height_wanted = (int) getPreferredSize().getHeight();
            addSize(table, row, column, height_wanted);
            height_wanted = findTotalMaximumRowSize(table, row);
            if (height_wanted != table.getRowHeight(row)) {
                table.setRowHeight(row, height_wanted);
            }
            return this;
        }

        @SuppressWarnings("unchecked")
        private void addSize(JTable table, int row, int column, int height) {
            Map rows = (Map) cellSizes.get(table);
            if (rows == null) {
                cellSizes.put(table, rows = new HashMap());
            }
            Map rowheights = (Map) rows.get(new Integer(row));
            if (rowheights == null) {
                rows.put(new Integer(row), rowheights = new HashMap());
            }
            rowheights.put(new Integer(column), new Integer(height));
        }

        /**
         * Look through all columns and get the renderer.  If it is
         * also a TextAreaRenderer, we look at the maximum height in
         * its hash table for this row.
         */
        private int findTotalMaximumRowSize(JTable table, int row) {
            int maximum_height = 0;
            Enumeration columns = table.getColumnModel().getColumns();
            while (columns.hasMoreElements()) {
                TableColumn tc = (TableColumn) columns.nextElement();
                TableCellRenderer cellRenderer = tc.getCellRenderer();
                if (cellRenderer instanceof TextAreaRenderer) {
                    TextAreaRenderer tar = (TextAreaRenderer) cellRenderer;
                    maximum_height = Math.max(maximum_height,
                            tar.findMaximumRowSize(table, row));
                }
            }
            return maximum_height;
        }

        private int findMaximumRowSize(JTable table, int row) {
            Map rows = (Map) cellSizes.get(table);
            if (rows == null) {
                return 0;
            }
            Map rowheights = (Map) rows.get(new Integer(row));
            if (rowheights == null) {
                return 0;
            }
            int maximum_height = 0;
            for (Iterator it = rowheights.entrySet().iterator();
                    it.hasNext();) {
                Map.Entry entry = (Map.Entry) it.next();
                int cellHeight = ((Integer) entry.getValue()).intValue();
                maximum_height = Math.max(maximum_height, cellHeight);
            }
            return maximum_height;
        }
    }
}

Answer 1

You need to have a renderer that uses a JTextPane, not a JTextArea, and then set the Document's style attributes.

i.e.,

static class TextAreaRenderer extends JTextPane implements TableCellRenderer {

  private final DefaultTableCellRenderer adaptee = new DefaultTableCellRenderer();
  /** map from table to map of rows to map of column heights */
  private final Map cellSizes = new HashMap();

  public TextAreaRenderer() {
     // !! setLineWrap(true);
     // setWrapStyleWord(true);

     StyledDocument doc = getStyledDocument();
     SimpleAttributeSet center = new SimpleAttributeSet();
     StyleConstants.setAlignment(center, StyleConstants.ALIGN_CENTER);
     doc.setParagraphAttributes(0, doc.getLength(), center, false);
  }

For more, see (and up-vote) camickr's answer here.