Member Avatar for Benjamin_4

i have a ComboBox named 'ComboBox_status' which have default values 'In Operation' and 'Disposed'
i want the background color to change to red when 'Disposed' is selected and green when 'In Operation' is selected.

this is the code i tried but it changes the background to red for both of them when they are selected

String age="Disposed";

        if("Disposed".equals(age)){
                  ComboBox_status.setBackground(Color.red); 
                  ComboBox_status.setForeground(Color.BLACK);
                }
                else{
                    ComboBox_status.setBackground(Color.GREEN);
                    ComboBox_status.setForeground(Color.darkGray);

                }

i will appreciate it if anyone could help me resolve this THANK YOU.

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  • 4 Replies
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  • Latest Post Latest Post by mKorbel

Dani AI

Generated

The problem in the original post by is that a fixed string was being tested instead of the JComboBox's actual selection, so the same branch is always executed. already pointed out the hardcoding issue and correctly suggested using a renderer — that is the most reliable way in Swing to control how the selected value (and the list items) are painted.

A concise, robust approach is to install a custom ListCellRenderer that sets background/foreground based on the item text. The renderer paints both the drop-down cells and the display area, and avoids look-and-feel quirks that can make direct calls to setBackground on the JComboBox ineffective.

comboBox.setRenderer(new DefaultListCellRenderer() {
    @Override
    public Component getListCellRendererComponent(JList<?> list, Object value,
            int index, boolean isSelected, boolean cellHasFocus) {
        super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
        setOpaque(true);
        String s = value == null ? "" : value.toString();
        if ("Disposed".equals(s)) {
            setBackground(Color.RED);
            setForeground(Color.BLACK);
        } else if ("In Operation".equals(s)) {
            setBackground(Color.GREEN);
            setForeground(Color.DARK_GRAY);
        } else {
            setBackground(list.getBackground());
            setForeground(list.getForeground());
        }
        return this;
    }
});

Notes and quick troubleshooting:

  • For editable JComboBox instances, the editor component must be colored separately via comboBox.getEditor().getEditorComponent().
  • If colors still do not appear, ensure the renderer component is opaque (setOpaque(true)) and call comboBox.repaint().
  • An alternative is to attach an ItemListener/ActionListener and change the combo box/editor background on selection, but many LAFs ignore setBackground on the combo itself — the renderer approach is more consistent.

Recommended Answers

All 4 Replies

Member Avatar for stultuske

how do you expect this to return false:

String age="Disposed";
if("Disposed".equals(age)){
Member Avatar for Benjamin_4

i know i need help
am new@java

Member Avatar for stultuske

basically: what you are doing is:

if ( true ) 
  setColor(RED);
else
  setColor(BLACK);

and for some reason, you expect the else block to be executed. don't hardcode the value of age, get the value selected in your JComboBox

Member Avatar for mKorbel

btw job for Renderer

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