Swing/ButtonsInListCell のバックアップ(No.11)

class ButtonsRenderer<E> extends JPanel implements ListCellRenderer<E> {
  protected static final Color EVEN_COLOR = new Color(0xE6_FF_E6);
  protected final JTextArea textArea = new JTextArea();
  protected final JButton deleteButton = new JButton("delete");
  protected final JButton copyButton = new JButton("copy");
  protected final List<JButton> buttons = Arrays.asList(deleteButton, copyButton);
  protected final DefaultListModel<E> model;
  protected int targetIndex;
  protected int pressedIndex = -1;
  protected int rolloverIndex = -1;
  protected JButton button;

  protected ButtonsRenderer(DefaultListModel<E> model) {
    super(new BorderLayout()); // *1
    this.model = model;
    setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 0));
    setOpaque(true);
    textArea.setLineWrap(true);
    textArea.setOpaque(false);
    add(textArea);

    deleteButton.addActionListener(e -> {
      boolean isMoreThanOneItem = model.getSize() > 1;
      if (isMoreThanOneItem) {
        model.remove(targetIndex);
      }
    });
    copyButton.addActionListener(e -> model.add(targetIndex, model.get(targetIndex)));

    Box box = Box.createHorizontalBox();
    buttons.forEach(b -> {
      b.setFocusable(false);
      b.setRolloverEnabled(false);
      box.add(b);
      box.add(Box.createHorizontalStrut(5));
    });
    add(box, BorderLayout.EAST);
  }

  @Override public Dimension getPreferredSize() {
    Dimension d = super.getPreferredSize();
    d.width = 0; // VerticalScrollBar as needed
    return d;
  }

  @Override public Component getListCellRendererComponent(
      JList<? extends E> list, E value, int index,
      boolean isSelected, boolean cellHasFocus) {
    textArea.setText(Objects.toString(value, ""));
    this.targetIndex = index;
    if (isSelected) {
      setBackground(list.getSelectionBackground());
      textArea.setForeground(list.getSelectionForeground());
    } else {
      setBackground(index % 2 == 0 ? EVEN_COLOR : list.getBackground());
      textArea.setForeground(list.getForeground());
    }
    buttons.forEach(ButtonsRenderer::resetButtonStatus);
    if (Objects.nonNull(button)) {
      if (index == pressedIndex) {
        button.getModel().setSelected(true);
        button.getModel().setArmed(true);
        button.getModel().setPressed(true);
      } else if (index == rolloverIndex) {
        button.getModel().setRollover(true);
      }
    }
    return this;
  }

  private static void resetButtonStatus(AbstractButton button) {
    ButtonModel model = button.getModel();
    model.setRollover(false);
    model.setArmed(false);
    model.setPressed(false);
    model.setSelected(false);
  }
}