Delete button in a JComboBox popup menu items

• download example.jar
• download src.zip
• repository

Code

class CellButtonsMouseListener extends MouseAdapter {
  @Override public void mouseMoved(MouseEvent e) {
    JList<?> list = (JList<?>) e.getComponent();
    Point pt = e.getPoint();
    int index = list.locationToIndex(pt);
    ButtonsRenderer<?> renderer = (ButtonsRenderer<?>) list.getCellRenderer();
    renderer.rolloverIndex = Objects.nonNull(getButton(list, pt, index)) ? index : -1;
    list.repaint();
  }

  @Override public void mousePressed(MouseEvent e) {
    e.getComponent().repaint();
  }

  @Override public void mouseReleased(MouseEvent e) {
    JList<?> list = (JList<?>) e.getComponent();
    Point pt = e.getPoint();
    int index = list.locationToIndex(pt);
    if (index >= 0) {
      JButton button = getButton(list, pt, index);
      if (Objects.nonNull(button)) {
        button.doClick();
      }
    }
    ((ButtonsRenderer<?>) list.getCellRenderer()).rolloverIndex = -1;
    list.repaint();
  }

  @Override public void mouseExited(MouseEvent e) {
    JList<?> list = (JList<?>) e.getComponent();
    ((ButtonsRenderer<?>) list.getCellRenderer()).rolloverIndex = -1;
  }

  private static <E> JButton getButton(JList<E> list, Point pt, int index) {
    E proto = list.getPrototypeCellValue();
    Component c = list.getCellRenderer().getListCellRendererComponent(
        list, proto, index, false, false);
    Rectangle r = list.getCellBounds(index, index);
    c.setBounds(r);
    // c.doLayout(); // may be needed for other layout managers (eg. FlowLayout)
    pt.translate(-r.x, -r.y);
    return Optional.ofNullable(SwingUtilities.getDeepestComponentAt(c, pt.x, pt.y))
        .filter(JButton.class::isInstance).map(JButton.class::cast).orElse(null);
  }
}

References

• Delete button in a JComboBox popup menu items(Japanese)