Use drag and drop to reorder a list : Drag Drop « Swing JFC « Java

Use drag and drop to reorder a list


import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.StringSelection;
import java.awt.datatransfer.Transferable;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DragGestureEvent;
import java.awt.dnd.DragGestureListener;
import java.awt.dnd.DragGestureRecognizer;
import java.awt.dnd.DragSource;
import java.awt.dnd.DragSourceDragEvent;
import java.awt.dnd.DragSourceDropEvent;
import java.awt.dnd.DragSourceEvent;
import java.awt.dnd.DragSourceListener;

import javax.swing.DefaultListModel;
import javax.swing.DropMode;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.TransferHandler;

public class DragDropList extends JList {
  DefaultListModel model;

  public DragDropList() {
    super(new DefaultListModel());
    model = (DefaultListModel) getModel();

    setTransferHandler(new MyListDropHandler(this));

    new MyDragListener(this);

  public static void main(String[] a){
    JFrame f = new JFrame();
    f.add(new JScrollPane(new DragDropList()));

class MyDragListener implements DragSourceListener, DragGestureListener {
  DragDropList list;

  DragSource ds = new DragSource();

  public MyDragListener(DragDropList list) {
    this.list = list;
    DragGestureRecognizer dgr = ds.createDefaultDragGestureRecognizer(list,
        DnDConstants.ACTION_MOVE, this);


  public void dragGestureRecognized(DragGestureEvent dge) {
    StringSelection transferable = new StringSelection(Integer.toString(list.getSelectedIndex()));
    ds.startDrag(dge, DragSource.DefaultCopyDrop, transferable, this);

  public void dragEnter(DragSourceDragEvent dsde) {

  public void dragExit(DragSourceEvent dse) {

  public void dragOver(DragSourceDragEvent dsde) {

  public void dragDropEnd(DragSourceDropEvent dsde) {
    if (dsde.getDropSuccess()) {
    } else {

  public void dropActionChanged(DragSourceDragEvent dsde) {

class MyListDropHandler extends TransferHandler {
  DragDropList list;

  public MyListDropHandler(DragDropList list) {
    this.list = list;

  public boolean canImport(TransferHandler.TransferSupport support) {
    if (!support.isDataFlavorSupported(DataFlavor.stringFlavor)) {
      return false;
    JList.DropLocation dl = (JList.DropLocation) support.getDropLocation();
    if (dl.getIndex() == -1) {
      return false;
    } else {
      return true;

  public boolean importData(TransferHandler.TransferSupport support) {
    if (!canImport(support)) {
      return false;

    Transferable transferable = support.getTransferable();
    String indexString;
    try {
      indexString = (String) transferable.getTransferData(DataFlavor.stringFlavor);
    } catch (Exception e) {
      return false;

    int index = Integer.parseInt(indexString);
    JList.DropLocation dl = (JList.DropLocation) support.getDropLocation();
    int dropTargetIndex = dl.getIndex();

    System.out.println(dropTargetIndex + " : ");
    return true;


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