Custom Table Cell Renderer Unable To Set Horizontal Alignment

Question

Hello,
I have a problem that I'm at my wit's end with, and I was hoping for some help.
I need to render the cells in my table differently (alignment, colors, etc) depending on the row AND the column, not just the column. I've got this working just fine, except for changing the cell's horizontal alignment won't work.
I have a CustomCellRenderer that extends DefaultTableCellRenderer and overrides the getTableCellRendererComponent() method, setting the foreground/background colors and horizontal alignment of the cell based on the cell's value.
I have a CustomTable that extends JTable and overrides the getCellRenderer(int row, int column) method to return a private instance of this CustomCellRenderer.
This works fine for foreground/background colors, but my calls to setHorizontalAlignment() in the getTableCellRendererComponent() seem to have no effect, every cell is always displayed LEFT aligned! It's almost like the cell's alignment is determined by something else than the table.getCellRenderer(row,column).getTableCellRendererComponent() method.
I've also tried setting the renderer for every existing TableColumn in the TableModel to this custom renderer, as well as overriding the table's getDefaultColumn() method to return this custom renderer as well for any Class parameter, with no success.
No matter what I've tried, I can customize the cell however I want, EXCEPT for the horizontal alignment!!!
Any ideas???
Here's the core custom classes that I'm using:
class CustomTable extends JTable {
private CustomRenderer customRenderer = new CustomRenderer();
public CustomTable() {
super();
public TableCellRenderer getCellRenderer(int row, int column) {
return customRenderer;
} // end class CustomTable
class CustomRenderer extends DefaultTableCellRenderer {
public CustomRenderer() {
super();
public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
super.getTableCellRendererComponent(table, value, isSelected, hasFocus, row, column);
if (row % 2 == 0) {
setForeground(Color.red);
setHorizontalAlignment(RIGHT);
} else {
setForeground(Color.blue);
setHorizontalAlignment(LEFT);
return this;
} // end class CustomRenderer
Even worse, I've gotten this to work fine in a trivial example I made to try and re-create the problem. But for some reason, this same thing is just not working for horizontal alignment in my actual project?!?
Anyone have any ideas how the cell's horizontal alignment set in the getTableCellRendererComponent() method is being ignored or overwritten before the cell is being displayed???
Thanks, any help is appreciated,
-Alex Blume

Answer 1

Ok, so I've looked into their source and I think I know where and what the trouble is. The JTable.java has a method called:
3658> public TableCellRenderer getCellRenderer(int row, int column) {
3659> TableColumn tableColumn = getColumnModel().getColumn(column);
3660> TableCellRenderer renderer = tableColumn.getCellRenderer();
3661> if (renderer == null) {
3662> renderer = getDefaultRenderer(getColumnClass(column));
3663> }
3664> return renderer;
3665> }
starting at line 3658 of their source code. It retrieves the TableCellRenderer on line 3660 by calling the tableColumn's getCellRenderer method. This is found in the TableColumn.java class:
421> public TableCellRenderer getCellRenderer() {
422> return cellRenderer;
423> }
See the problem? Only ONE cell Renderer. It's referring to a variable found at line 140 which is of type TableCellRenderer ... well actually it's created as a DefaultTableCellRenderer at some point since TableCellRenderer is an interface.
Basically the fix is this:
In the TableColumn.java file, a collection (Vector, LinkedList, whatever) needs to keep track of each cell's renderer. This will solve the solution. Of course this will be something that you or I can make.
What's funny is the contradiction in documentation between JTable's and TableColumn's getCellRenderer() method. First, if we look at TableColumn's documentation it states:
"Returns the TableCellRenderer used by the JTable to draw values for this column."
Based on that first statement, the getCellRenderer() method in TableColumn is doing its job exactly. No lies, no contradictions in what it does.
However, that method is called up inside of the JTable's getCellRenderer() method which says a completely different thing which is:
"Returns an appropriate renderer for the cell specified by this row and column."
Now we have a problem. For the cell specified. It appears that the rush to push this out blinded some developer who either:
1) mis-interpreted what the JTable getCellRenderer() method was supposed to do and inadvertently added a feature or;
2) was in a 2 a.m. blitz, wired on Pepsi and adrenalin and wrote the bug in.
Either way, I'm really hoping that they'll fix this because it will take care of at least 2 bugs. Btw, anyone interested in posting a subclass to solve this problem (subclass of TableColumn) is more than welcome. I've spent much too much time on this and my project is already behind so I can't really afford any more time on this.
later,
a.