The major issues I can see are you are mixing two different API’s. You’re using both the low level D’n’D API and the newer “component D’n’D” API.
Personally, the newer API annoys me, so I tend to avoid it.
I can’t see why you need to transfer the label, when it would be better to transfer the underlying PublicUser object, but that’s just me.
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
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 java.awt.dnd.DropTarget;
import java.awt.dnd.DropTargetDragEvent;
import java.awt.dnd.DropTargetDropEvent;
import java.awt.dnd.DropTargetEvent;
import java.awt.dnd.DropTargetListener;
import java.io.IOException;
import javax.swing.DefaultListModel;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TestDnD {
public static void main(String[] args) {
new TestDnD();
}
public TestDnD() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException ex) {
} catch (InstantiationException ex) {
} catch (IllegalAccessException ex) {
} catch (UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JList list;
public TestPane() {
setLayout(new BorderLayout());
list = new JList();
DefaultListModel model = new DefaultListModel();
model.addElement(new User("Shaun"));
model.addElement(new User("Andy"));
model.addElement(new User("Luke"));
model.addElement(new User("Han"));
model.addElement(new User("Liea"));
model.addElement(new User("Yoda"));
list.setModel(model);
add(new JScrollPane(list), BorderLayout.WEST);
DragGestureRecognizer dgr = DragSource.getDefaultDragSource().createDefaultDragGestureRecognizer(
list,
DnDConstants.ACTION_COPY_OR_MOVE,
new DragGestureHandler(list));
JPanel panel = new JPanel(new GridBagLayout());
add(panel);
DropTarget dt = new DropTarget(
panel,
DnDConstants.ACTION_COPY_OR_MOVE,
new DropTargetHandler(panel),
true);
}
}
public static class User {
private String name;
public User(String name) {
this.name = name;
}
public String getName() {
return name;
}
@Override
public String toString() {
return name;
}
}
public static class UserTransferable implements Transferable {
public static final DataFlavor USER_DATA_FLAVOR = new DataFlavor(User.class, "User");
private User user;
public UserTransferable(User user) {
this.user = user;
}
@Override
public DataFlavor[] getTransferDataFlavors() {
return new DataFlavor[]{USER_DATA_FLAVOR};
}
@Override
public boolean isDataFlavorSupported(DataFlavor flavor) {
return USER_DATA_FLAVOR.equals(flavor);
}
@Override
public Object getTransferData(DataFlavor flavor) throws UnsupportedFlavorException, IOException {
Object value = null;
if (USER_DATA_FLAVOR.equals(flavor)) {
value = user;
} else {
throw new UnsupportedFlavorException(flavor);
}
return value;
}
}
protected class DragGestureHandler implements DragGestureListener {
private JList list;
public DragGestureHandler(JList list) {
this.list = list;
}
@Override
public void dragGestureRecognized(DragGestureEvent dge) {
Object selectedValue = list.getSelectedValue();
if (selectedValue instanceof User) {
User user = (User) selectedValue;
Transferable t = new UserTransferable(user);
DragSource ds = dge.getDragSource();
ds.startDrag(
dge,
null,
t,
new DragSourceHandler());
}
}
}
protected class DragSourceHandler implements DragSourceListener {
public void dragEnter(DragSourceDragEvent dsde) {
}
public void dragOver(DragSourceDragEvent dsde) {
}
public void dropActionChanged(DragSourceDragEvent dsde) {
}
public void dragExit(DragSourceEvent dse) {
}
public void dragDropEnd(DragSourceDropEvent dsde) {
System.out.println("Drag ended...");
}
}
protected class DropTargetHandler implements DropTargetListener {
private JPanel panel;
public DropTargetHandler(JPanel panel) {
this.panel = panel;
}
public void dragEnter(DropTargetDragEvent dtde) {
if (dtde.getTransferable().isDataFlavorSupported(UserTransferable.USER_DATA_FLAVOR)) {
System.out.println("Accept...");
dtde.acceptDrag(DnDConstants.ACTION_COPY_OR_MOVE);
} else {
System.out.println("Drag...");
dtde.rejectDrag();
}
}
public void dragOver(DropTargetDragEvent dtde) {
}
public void dropActionChanged(DropTargetDragEvent dtde) {
}
public void dragExit(DropTargetEvent dte) {
}
public void drop(DropTargetDropEvent dtde) {
System.out.println("Dropped...");
if (dtde.getTransferable().isDataFlavorSupported(UserTransferable.USER_DATA_FLAVOR)) {
Transferable t = dtde.getTransferable();
if (t.isDataFlavorSupported(UserTransferable.USER_DATA_FLAVOR)) {
try {
Object transferData = t.getTransferData(UserTransferable.USER_DATA_FLAVOR);
if (transferData instanceof User) {
User user = (User) transferData;
dtde.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
panel.add(new JLabel(user.getName()));
panel.revalidate();
panel.repaint();
} else {
dtde.rejectDrop();
}
} catch (UnsupportedFlavorException ex) {
ex.printStackTrace();
dtde.rejectDrop();
} catch (IOException ex) {
ex.printStackTrace();
dtde.rejectDrop();
}
} else {
dtde.rejectDrop();
}
}
}
}
}