TableCellRenderer causes buggy graphics and is called again and again

Question

I want to create a table with variable cell-hights, depending on the
number of lines that shall appear. This works by my following Renderer
(a JTextArea). But when I move my JDialog (or I also tried JFrame)
containing my JTable (inside of a scrollpane, of course) around, there
are still intermediate dialog-positions on the screen.
Another problem is, that the method getTableCellRendererComponent()
is called over and over again, as long as the dialog exists.
Here is the code of the Renderer:
private class MyTableRenderer extends JTextArea implements TableCellRenderer
          public MyTableRenderer()
               super();
               setOpaque(true);
          public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column)
               Log.info("MyTableRenderer", "getTableCellRendererComponent() called");
               String s = (String) value;
               int count = 1, i;
               if (s != null) {
                    for (i=0; i<s.length(); i++) {
                         if (s.charAt(i) == '\n')
                              count++;
               table.setRowHeight(row, 17*count+4);
               setText(s);
               if (isSelected || hasFocus) {
                    setForeground(Color.white);
                    setBackground(Color.red);
               } else {
                    setForeground(Color.black);
                    setBackground(Color.white);
               return this;
     private MyTableRenderer myRenderer = new MyTableRenderer();
Later in my dialog-constructor I do the following:
try {
               Class cc = Class.forName("java.lang.String");
               table.setDefaultRenderer(cc, myRenderer);
          } catch (Exception e) {}
By the way: MyTableCellRenderer is a inner class of my dialog-class.
Please help

Answer 1

Yes, you are right: The graphics is caused by the infinite loop
and the infinite loop is caused by setRowHeight().
To make sure it is called only once per row I intoduced a Hashtable rowHeights to store the old heights of earch row. setRowHeight() is
now only called, when there is nothing in the Hashtable for the
current row, or if the size of the Hashtable and the preferred size
(another improvement) are different. Here is the working code for my
Renderer:
     private class MyTableRenderer extends JTextArea implements TableCellRenderer
          Hashtable rowHeights = new Hashtable();
          public MyTableRenderer()
               super();
               setLineWrap(true);
               setWrapStyleWord(true);
               setOpaque(true);
          public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column)
               Log.info("MyTableRenderer", "getTableCellRendererComponent() called: row="+row+", col="+column);
               if (column == 0) {     
                    String s = (String) value;
                    if (s != null && !s.equals("")) {               
                         setText(s);
                         Integer oldHeight = (Integer) rowHeights.get(new Integer(row));
                         Integer newHeight = new Integer(/*17*count+4*/ getPreferredSize().height);
                         if (oldHeight == null || !oldHeight.equals(newHeight)) {
                              rowHeights.put(new Integer(row), newHeight);
                              table.setRowHeight(row, /*17*count+4*/ newHeight.intValue());
                    if (isSelected || hasFocus) {
                         setForeground(Color.white);
                         setBackground(Color.red);
                    } else {
                         setForeground(Color.black);
                         setBackground(Color.white);
               return this;
Thanks a lot !