Changing the colour of specific index using JList

Question

How can I change the colour of a specific index using JList, I manage to change the colour, but it changes the colour of the whole list and I need to be able to change a specific index to one colour, and another index to another.

I've tried quite a lot of combinations and they seem to only change the whole list colour instead of the index. I understand why because it's referring to the whole list, I just don't know how to change it for a specific index.

    m.aList.setCellRenderer(new MyCellRender());

  private class MyCellRender extends DefaultListCellRenderer  
{    

    public Component getListCellRendererComponent( JList list,  
            Object value, int index, boolean isSelected,  
            boolean cellHasFocus )  
    {  
        super.getListCellRendererComponent( list, value, index,  
                isSelected, cellHasFocus );  

        ArrayList<Object> values = new ArrayList<>();
        ArrayList<String> complete = new ArrayList<>();
        ArrayList<String> incomplete = new ArrayList<>();

        for (int i = 0; i < list.getModel().getSize(); i++) {
            values.add(list.getModel().getElementAt(i));
        }

        for (Object o : values) {
           if (o.toString().contains("COMPLETED")) {
               complete.add(o.toString());
           }
           if (o.toString().contains("INCOMPLETE")) {
               incomplete.add(o.toString());
           }
        }

        for (String s : complete) {
            setForeground(Color.green);
        }
        for (String s1 : incomplete) {
            setForeground(Color.red);
        }

        return( this );  
    }  
}

The values in the list contain either COMPLETED, or INCOMPLETE, and I would like to change their colour according to their value.

I'm using a ListCellRenderer, this is a snippet of code that I'm trying to use to change the colour, however, it changes the colour of the whole list instead of the index I want — user1848712, Jan 03 '14 at 16:27
then post a full `SSCCE` of your code to show how the problem is occurring — Reimeus, Jan 03 '14 at 16:29

score 6 · Accepted Answer · answered Jan 03 '14 at 16:51

The values in the list contain either COMPLETED, or INCOMPLETE, and I would like to change their colour according to their value.

First off there's no need to keep these three lists:

ArrayList<Object> values = new ArrayList<>();
ArrayList<String> complete = new ArrayList<>();
ArrayList<String> incomplete = new ArrayList<>();

The ListCellRenderer component is evaluated for each element in the JList so these lists are pointless. You can implement your requirement easily doing as follows:

private class MyCellRender extends DefaultListCellRenderer {
   @Override
   public Component getListCellRendererComponent(JList<?> list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
       super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
       if(value.toString().contains("INCOMPLETE") ||  value.toString().contains("COMPLETED")) {
           Color fg = value.toString().contains("COMPLETED") ? Color.green : Color.red;
           setForeground(fg);
       } else {
           setForeground(list.getForeground());
       }
       return this;
   }
}

Take a look to Writing a Custom Cell Renderer section in How to Use Lists trail for further details.

Thankyou very much, don't have much understanding as to how cell renderers work so I'll read up on it — user1848712, Jan 03 '14 at 16:56
@user1848712 you're welcome! Take a look to [this topic](http://stackoverflow.com/a/13673083/1795530) for a better understaing about how Swing renderers work. — dic19, Jan 03 '14 at 17:03

score 1 · Answer 2 · answered Jan 03 '14 at 16:51

Youre setting the foreground color for every list component but getListCellRendererComponent is called when rendering every individual cell. In that case you need to do something like

if (value.toString().contains("COMPLETED")) {
    setForeground(Color.GREEN);
} else if (value.toString().contains("INCOMPLETE")) {
    setForeground(Color.RED);           
} else {   // handle default case
   ...
}

This is the only user code needed in the ListRenderer

Changing the colour of specific index using JList

2 Answers2