Move items by copying and pasting between JLists

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

Code

class ListPopupMenu extends JPopupMenu {
  private final JMenuItem cutItem;
  private final JMenuItem copyItem;
  protected ListPopupMenu(JList list) {
    super();
    Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
    TransferHandler handler = list.getTransferHandler();
    cutItem = add("cut");
    cutItem.addActionListener(e -> {
      handler.exportToClipboard(list, clipboard, TransferHandler.MOVE);
    });
    copyItem = add("copy");
    copyItem.addActionListener(e -> {
      handler.exportToClipboard(list, clipboard, TransferHandler.COPY);
    });
    add("paste").addActionListener(e -> {
      handler.importData(list, clipboard.getContents(null));
    });
    addSeparator();
    add("clearSelection").addActionListener(e -> list.clearSelection());
  }
  @Override public void show(Component c, int x, int y) {
    if (c instanceof JList) {
      boolean isSelected = !((JList) c).isSelectionEmpty();
      cutItem.setEnabled(isSelected);
      copyItem.setEnabled(isSelected);
      super.show(c, x, y);
    }
  }
}

// ...
private static int getIndex(TransferHandler.TransferSupport info) {
  JList target = (JList) info.getComponent();
  int index; // = dl.getIndex();
  if (info.isDrop()) { // Mouse Drag & Drop
    System.out.println("Mouse Drag & Drop");
    TransferHandler.DropLocation tdl = info.getDropLocation();
    if (tdl instanceof JList.DropLocation) {
      index = ((JList.DropLocation) tdl).getIndex();
    } else {
      index = target.getSelectedIndex();
    }
  } else { // Keyboard Copy & Paste
    index = target.getSelectedIndex();
  }
  DefaultListModel listModel = (DefaultListModel) target.getModel();
  // boolean insert = dl.isInsert();
  int max = listModel.getSize();
  // int index = dl.getIndex();
  index = index < 0 ? max : index; // If it is out of range, it is appended to the end
  index = Math.min(index, max);
  return index;
}

References

• Move items by copying and pasting between JLists(Japanese)