Swing/DnDReorderList のバックアップ(No.18)

class ListItemTransferHandler extends TransferHandler {
  private final DataFlavor localObjectFlavor;
  private Object[] transferedObjects = null;
  public ListItemTransferHandler() {
    localObjectFlavor = new ActivationDataFlavor(
      Object[].class, DataFlavor.javaJVMLocalObjectMimeType, "Array of items");
  }
  @Override protected Transferable createTransferable(JComponent c) {
    JList list = (JList) c;
    indices = list.getSelectedIndices();
    transferedObjects = list.getSelectedValues();
    return new DataHandler(transferedObjects, localObjectFlavor.getMimeType());
  }
  @Override public boolean canImport(TransferSupport info) {
    if (!info.isDrop() || !info.isDataFlavorSupported(localObjectFlavor)) {
      return false;
    }
    return true;
  }
  @Override public int getSourceActions(JComponent c) {
    return TransferHandler.MOVE; //TransferHandler.COPY_OR_MOVE;
  }
  @Override public boolean importData(TransferSupport info) {
    if (!canImport(info)) {
      return false;
    }
    JList target = (JList) info.getComponent();
    JList.DropLocation dl = (JList.DropLocation) info.getDropLocation();
    DefaultListModel listModel = (DefaultListModel) target.getModel();
    int index = dl.getIndex();
    //boolean insert = dl.isInsert();
    int max = listModel.getSize();
    if (index < 0 || index > max) {
      index = max;
    }
    addIndex = index;

    try {
      Object[] values =
        (Object[]) info.getTransferable().getTransferData(localObjectFlavor);
      addCount = values.length;
      for (int i = 0; i < values.length; i++) {
        int idx = index++;
        listModel.add(idx, values[i]);
        target.addSelectionInterval(idx, idx);
      }
      return true;
    } catch (UnsupportedFlavorException | IOException ex) {
      ex.printStackTrace();
    }
    return false;
  }
  @Override protected void exportDone(
      JComponent c, Transferable data, int action) {
    cleanup(c, action == TransferHandler.MOVE);
  }
  private void cleanup(JComponent c, boolean remove) {
    if (remove && indices != null) {
      JList source = (JList) c;
      DefaultListModel model  = (DefaultListModel) source.getModel();
      if (addCount > 0) {
        for (int i = 0; i < indices.length; i++) {
          if (indices[i] >= addIndex) {
            indices[i] += addCount;
          }
        }
      }
      for (int i = indices.length - 1; i >= 0; i--) {
        model.remove(indices[i]);
      }
    }
    indices  = null;
    addCount = 0;
    addIndex = -1;
  }
  private int[] indices = null;
  private int addIndex  = -1; //Location where items were added
  private int addCount  = 0;  //Number of items added.
}