Swing/TreeComboBox のバックアップ(No.10)

class TreeComboBox<E extends TreeNode> extends JComboBox<E> {
  private boolean isNotSelectableIndex;
  private final Action up = new AbstractAction() {
    @Override public void actionPerformed(ActionEvent e) {
      int si = getSelectedIndex();
      for (int i = si - 1; i >= 0; i--) {
        if (getItemAt(i).isLeaf()) {
          setSelectedIndex(i);
          break;
        }
      }
    }
  };
  private final Action down = new AbstractAction() {
    @Override public void actionPerformed(ActionEvent e) {
      int si = getSelectedIndex();
      for (int i = si + 1; i < getModel().getSize(); i++) {
        if (getItemAt(i).isLeaf()) {
          setSelectedIndex(i);
          break;
        }
      }
    }
  };
  @Override public void updateUI() {
    super.updateUI();
    ListCellRenderer<? super E> renderer = getRenderer();
    setRenderer(new ListCellRenderer<E>() {
      @Override public Component getListCellRendererComponent(
          JList<? extends E> list, E value, int index,
          boolean isSelected, boolean cellHasFocus) {
        JLabel l = (JLabel) renderer.getListCellRendererComponent(
            list, value, index, isSelected, cellHasFocus);
        l.setBorder(BorderFactory.createEmptyBorder(1, 1, 1, 1));
        if (index >= 0 && value instanceof DefaultMutableTreeNode) {
          DefaultMutableTreeNode node = (DefaultMutableTreeNode) value;
          int indent = Math.max(0, node.getLevel() - 1) * 16;
          l.setBorder(BorderFactory.createEmptyBorder(1, indent + 1, 1, 1));
          if (!value.isLeaf()) {
            l.setForeground(Color.WHITE);
            l.setBackground(Color.GRAY.darker());
          }
        }
        return l;
      }
    });
    EventQueue.invokeLater(() -> {
      ActionMap am = getActionMap();
      am.put("selectPrevious3", up);
      am.put("selectNext3", down);
      InputMap im = getInputMap();
      im.put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), "selectPrevious3");
      im.put(KeyStroke.getKeyStroke(KeyEvent.VK_KP_UP, 0), "selectPrevious3");
      im.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0), "selectNext3");
      im.put(KeyStroke.getKeyStroke(KeyEvent.VK_KP_DOWN, 0), "selectNext3");
    });
  }
  @Override public void setPopupVisible(boolean v) {
    if (!v && isNotSelectableIndex) {
      isNotSelectableIndex = false;
    } else {
      super.setPopupVisible(v);
    }
  }
  @Override public void setSelectedIndex(int index) {
    TreeNode node = getItemAt(index);
    if (Objects.nonNull(node) && node.isLeaf()) {
      super.setSelectedIndex(index);
    } else {
      isNotSelectableIndex = true;
    }
  }
}