Set tree DropMode to DropMode.USE_SELECTION : Drag Drop « Swing « Java Tutorial

1. Java Tutorial
2. Swing
3. Drag Drop

import java.awt.BorderLayout;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;

import javax.swing.DropMode;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.JTree;
import javax.swing.TransferHandler;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreePath;

public class DndTree {
  public static void main(String args[]) {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JPanel top = new JPanel(new BorderLayout());
    JLabel dragLabel = new JLabel("Drag me:");
    JTextField text = new JTextField();
    text.setDragEnabled(true);
    top.add(dragLabel, BorderLayout.WEST);
    top.add(text, BorderLayout.CENTER);
    f.add(top, BorderLayout.NORTH);

    final JTree tree = new JTree();
    final DefaultTreeModel model = (DefaultTreeModel) tree.getModel();
    tree.setTransferHandler(new TransferHandler() {
      public boolean canImport(TransferHandler.TransferSupport support) {
        if (!support.isDataFlavorSupported(DataFlavor.stringFlavor) || !support.isDrop()) {
          return false;
        }
        JTree.DropLocation dropLocation = (JTree.DropLocation) support.getDropLocation();
        return dropLocation.getPath() != null;
      }

      public boolean importData(TransferHandler.TransferSupport support) {
        if (!canImport(support)) {
          return false;
        }
        JTree.DropLocation dropLocation = (JTree.DropLocation) support.getDropLocation();
        TreePath path = dropLocation.getPath();
        Transferable transferable = support.getTransferable();

        String transferData;
        try {
          transferData = (String) transferable.getTransferData(DataFlavor.stringFlavor);
        } catch (IOException e) {
          return false;
        } catch (UnsupportedFlavorException e) {
          return false;
        }

        int childIndex = dropLocation.getChildIndex();
        if (childIndex == -1) {
          childIndex = model.getChildCount(path.getLastPathComponent());
        }

        DefaultMutableTreeNode newNode = new DefaultMutableTreeNode(transferData);
        DefaultMutableTreeNode parentNode = (DefaultMutableTreeNode) path.getLastPathComponent();
        model.insertNodeInto(newNode, parentNode, childIndex);

        TreePath newPath = path.pathByAddingChild(newNode);
        tree.makeVisible(newPath);
        tree.scrollRectToVisible(tree.getPathBounds(newPath));
        return true;
      }
    });

    JScrollPane pane = new JScrollPane(tree);
    f.add(pane, BorderLayout.CENTER);

    tree.setDropMode(DropMode.USE_SELECTION);
    f.setSize(300, 400);
    f.setVisible(true);
  }
}

14.112.Drag Drop
	14.112.1.	Basic drag and drop
	14.112.2.	Dragging Text from a JLabel
	14.112.3.	Drag-and-Drop Support for Images
	14.112.4.	Drag and drop icons: use an icon property.
	14.112.5.	implements DragGestureListener, Transferable
	14.112.6.	Dragging and dropping text between a text area, a list, and a table
	14.112.7.	Drag and drop between JTextArea and JTextField
	14.112.8.	Transfer both Text and Color between JTextField and JTextArea
	14.112.9.	Drag and drop between JList and JTextField
	14.112.10.	DropMode.ON
	14.112.11.	DropMode.INSERT
	14.112.12.	DropMode.ON_OR_INSERT
	14.112.13.	Set tree DropMode to DropMode.USE_SELECTION
	14.112.14.	Set tree drag mode to DropMode.ON
	14.112.15.	Set tree drag mode to DropMode.INSERT
	14.112.16.	Set tree drag mode to DropMode.ON_OR_INSERT
	14.112.17.	Choose Drop Action
	14.112.18.	Various drop actions
	14.112.19.	JTable drag and drop
	14.112.20.	Create a drag source a drop target and a transferable object.
	14.112.21.	Making a Component Draggable
	14.112.22.	Detect a drag initiating gesture in your application
	14.112.23.	Illustrates cut, copy, paste and drag and drop using three instances of JList
	14.112.24.	Location sensitive drag and drop
	14.112.25.	Demonstration of the top-level TransferHandler support on JFrame
	14.112.26.	Drag-and-Drop customization: drag the foreground color from the first label and drop it as the background color into the second one
	14.112.27.	Demonstrates how to add copy and drag support to a Swing component with TransferHandler
	14.112.28.	ScribblePane allows individual PolyLine lines to be selected, cut, copied, pasted, dragged, and dropped
	14.112.29.	Built-in drag and drop support: utilize a TransferHandler class
	14.112.30.	DND Drag and drop List