Question

I’m trying to add several JLabels to a JPanel along with mouse listeners using a loop. These JLabels are going to have mouse listeners so that they change their icon when clicked (Using label.setIcon()). However, I only want to have one “selected” at a time. So, I need them to know when another label is clicked so it knows to turn itself off before the new label gets selected. However, my problem is that because I’m adding these labels with a loop they all have the same MouseListener.

Can anyone teach me a simple way to accomplish this?

Answer 1

This is a short example, how you could implement it (please note, that I didn’t use the icon, but change the label instead):

public class MouseListenerExample extends JFrame {

    public static class MyMouseListener extends MouseAdapter {
        private static final Collection<JLabel> labels = new ArrayList<JLabel>();
        private final JFrame frame;

        public MyMouseListener(JFrame frame, JLabel label) {
            this.frame = frame;
            labels.add(label);
        }

        @Override
        public void mouseClicked(MouseEvent e) {
            for (JLabel label : labels) {
                String text = label.getText();
                if (text.startsWith("X ")) {
                    label.setText(text.substring(2));
                }
            }
            JLabel currentLabel = (JLabel) e.getComponent();
            currentLabel.setText("X " + currentLabel.getText());
        }

    }

    public MouseListenerExample() {
        super("MouseListener Example");
        Container c = getContentPane();
        c.setLayout(new FlowLayout());
        for (int i = 0; i < 10; i++) {
            JLabel jLabel = new JLabel("Label " + i);
            c.add(jLabel);
            jLabel.addMouseListener(new MyMouseListener(this, jLabel));
        }
        pack();
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);
    }

    public static void main(String[] args) {
        new MouseListenerExample();
    }
}

The main idea is, that you create a new MouseListener for each label, but keep a list of labels outside of each listener’s scope (in this example I just use a static variable, but you could also have a field containing the list of labels in the frame.