Changing JTable cell color

Question

This is driving me absolutely insane.

I know that, to change the formatting of table cells with JTable, I have to use my own renderer. But I cannot seem to implement this properly.

This is my current setup:

public class MyClass
{
    public static void main(String args[])
    {
        JTable myTable = new JTable(10, 10);
        myTable.setDefaultRenderer ([I dont know what to put here], new CustomRenderer());
    }
}

class CustomRenderer extends DefaultTableCellRenderer 
{
    public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column)
    {
        Component c = super.getTableCellRendererComponent(table, value, isSelected, hasFocus, row, column);

        // Formatting
        return c;
    }
}

What do I need to use for the first parameter of setDefaultRenderer ? The API just says 'class'. I have no idea what to put there.

Could someone just explain, in the simplest of terms, how I go about implementing this? Please provide an example of how I can change the formatting from within the main() method as well.

Answer 1

In the first parameter for setDefaultRenderer , put the class literal for the Class that you want to override rendering. Ie, if your data consist all of strings, you can put

myTable.setDefaultRenderer(String.class, new CustomRenderer());

If your data also consists of values with BigDecimal or Integer as classes, you have to invoke that method several times for each class type ( BigDecimal.class or Integer.class in each case).

And finally, to change the background color you do this in your renderer:

class CustomRenderer extends DefaultTableCellRenderer 
{
    public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column)
    {
        Component c = super.getTableCellRendererComponent(table, value, isSelected, hasFocus, row, column);
        c.setBackground(new java.awt.Color(255, 72, 72));
        return c;
    }
}

If you write a renderer that should work for all classes of an interface , you will also need to modify the getColumnClass function of your table model and let it return the interface class for all objects that implement this interface:

public Class<? extends Object> getColumnClass(int c) {
    Object object = getValueAt(0, c);
    if(object == null) {
        return Object.class;
    if(getValueAt(0, c) instanceof IColorable) {
        return ICarPart.class;
    } else {
        return getValueAt(0, c).getClass();
    }
}

With that one can register a renderer for IColorable.class and does not need to register a separate renderer for each implementation.