DnD (drag and drop)JTree code : Tree « Swing JFC « Java

DnD (drag and drop)JTree code

DnD (drag and drop)JTree code
Java Swing, 2nd Edition
By Marc Loy, Robert Eckstein, Dave Wood, James Elliott, Brian Cole
ISBN: 0-596-00408-7
Publisher: O'Reilly 
// TreeDragTest.java
//A simple starting point for testing the DnD JTree code.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Insets;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.dnd.Autoscroll;
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.DropTargetContext;
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.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeNode;
import javax.swing.tree.TreePath;

public class TreeDragTest extends JFrame {

  TreeDragSource ds;

  TreeDropTarget dt;

  JTree tree;

  public TreeDragTest() {
    super("Rearrangeable Tree");
    setSize(300, 200);

    // If you want autoscrolling, use this line:
    tree = new AutoScrollingJTree();
    // Otherwise, use this line:
    //tree = new JTree();
    getContentPane().add(new JScrollPane(tree), BorderLayout.CENTER);

    // If we only support move operations...
    //ds = new TreeDragSource(tree, DnDConstants.ACTION_MOVE);
    ds = new TreeDragSource(tree, DnDConstants.ACTION_COPY_OR_MOVE);
    dt = new TreeDropTarget(tree);

  public class AutoScrollingJTree extends JTree implements Autoscroll {
    private int margin = 12;

    public AutoScrollingJTree() {

    public void autoscroll(Point p) {
      int realrow = getRowForLocation(p.x, p.y);
      Rectangle outer = getBounds();
      realrow = (p.y + outer.y <= margin ? realrow < 1 ? 0 : realrow - 1
          : realrow < getRowCount() - 1 ? realrow + 1 : realrow);

    public Insets getAutoscrollInsets() {
      Rectangle outer = getBounds();
      Rectangle inner = getParent().getBounds();
      return new Insets(inner.y - outer.y + margin, inner.x - outer.x
          + margin, outer.height - inner.height - inner.y + outer.y
          + margin, outer.width - inner.width - inner.x + outer.x
          + margin);

    // Use this method if you want to see the boundaries of the
    // autoscroll active region

    public void paintComponent(Graphics g) {
      Rectangle outer = getBounds();
      Rectangle inner = getParent().getBounds();
      g.drawRect(-outer.x + 12, -outer.y + 12, inner.width - 24,
          inner.height - 24);


  public static void main(String args[]) {
    new TreeDragTest();

//A drag source wrapper for a JTree. This class can be used to make
//a rearrangeable DnD tree with the TransferableTreeNode class as the
//transfer data type.

class TreeDragSource implements DragSourceListener, DragGestureListener {

  DragSource source;

  DragGestureRecognizer recognizer;

  TransferableTreeNode transferable;

  DefaultMutableTreeNode oldNode;

  JTree sourceTree;

  public TreeDragSource(JTree tree, int actions) {
    sourceTree = tree;
    source = new DragSource();
    recognizer = source.createDefaultDragGestureRecognizer(sourceTree,
        actions, this);

   * Drag Gesture Handler
  public void dragGestureRecognized(DragGestureEvent dge) {
    TreePath path = sourceTree.getSelectionPath();
    if ((path == null) || (path.getPathCount() <= 1)) {
      // We can't move the root node or an empty selection
    oldNode = (DefaultMutableTreeNode) path.getLastPathComponent();
    transferable = new TransferableTreeNode(path);
    source.startDrag(dge, DragSource.DefaultMoveNoDrop, transferable, this);

    // If you support dropping the node anywhere, you should probably
    // start with a valid move cursor:
    //source.startDrag(dge, DragSource.DefaultMoveDrop, transferable,
    // this);

   * Drag Event Handlers
  public void dragEnter(DragSourceDragEvent dsde) {

  public void dragExit(DragSourceEvent dse) {

  public void dragOver(DragSourceDragEvent dsde) {

  public void dropActionChanged(DragSourceDragEvent dsde) {
    System.out.println("Action: " + dsde.getDropAction());
    System.out.println("Target Action: " + dsde.getTargetActions());
    System.out.println("User Action: " + dsde.getUserAction());

  public void dragDropEnd(DragSourceDropEvent dsde) {
     * to support move or copy, we have to check which occurred:
    System.out.println("Drop Action: " + dsde.getDropAction());
    if (dsde.getDropSuccess()
        && (dsde.getDropAction() == DnDConstants.ACTION_MOVE)) {
      ((DefaultTreeModel) sourceTree.getModel())

     * to support move only... if (dsde.getDropSuccess()) {
     * ((DefaultTreeModel)sourceTree.getModel()).removeNodeFromParent(oldNode); }

//A quick DropTarget that's looking for drops from draggable JTrees.

class TreeDropTarget implements DropTargetListener {

  DropTarget target;

  JTree targetTree;

  public TreeDropTarget(JTree tree) {
    targetTree = tree;
    target = new DropTarget(targetTree, this);

   * Drop Event Handlers
  private TreeNode getNodeForEvent(DropTargetDragEvent dtde) {
    Point p = dtde.getLocation();
    DropTargetContext dtc = dtde.getDropTargetContext();
    JTree tree = (JTree) dtc.getComponent();
    TreePath path = tree.getClosestPathForLocation(p.x, p.y);
    return (TreeNode) path.getLastPathComponent();

  public void dragEnter(DropTargetDragEvent dtde) {
    TreeNode node = getNodeForEvent(dtde);
    if (node.isLeaf()) {
    } else {
      // start by supporting move operations

  public void dragOver(DropTargetDragEvent dtde) {
    TreeNode node = getNodeForEvent(dtde);
    if (node.isLeaf()) {
    } else {
      // start by supporting move operations

  public void dragExit(DropTargetEvent dte) {

  public void dropActionChanged(DropTargetDragEvent dtde) {

  public void drop(DropTargetDropEvent dtde) {
    Point pt = dtde.getLocation();
    DropTargetContext dtc = dtde.getDropTargetContext();
    JTree tree = (JTree) dtc.getComponent();
    TreePath parentpath = tree.getClosestPathForLocation(pt.x, pt.y);
    DefaultMutableTreeNode parent = (DefaultMutableTreeNode) parentpath
    if (parent.isLeaf()) {

    try {
      Transferable tr = dtde.getTransferable();
      DataFlavor[] flavors = tr.getTransferDataFlavors();
      for (int i = 0; i < flavors.length; i++) {
        if (tr.isDataFlavorSupported(flavors[i])) {
          TreePath p = (TreePath) tr.getTransferData(flavors[i]);
          DefaultMutableTreeNode node = (DefaultMutableTreeNode) p
          DefaultTreeModel model = (DefaultTreeModel) tree.getModel();
          model.insertNodeInto(node, parent, 0);
    } catch (Exception e) {

//A Transferable TreePath to be used with Drag & Drop applications.

class TransferableTreeNode implements Transferable {

  public static DataFlavor TREE_PATH_FLAVOR = new DataFlavor(TreePath.class,
      "Tree Path");

  DataFlavor flavors[] = { TREE_PATH_FLAVOR };

  TreePath path;

  public TransferableTreeNode(TreePath tp) {
    path = tp;

  public synchronized DataFlavor[] getTransferDataFlavors() {
    return flavors;

  public boolean isDataFlavorSupported(DataFlavor flavor) {
    return (flavor.getRepresentationClass() == TreePath.class);

  public synchronized Object getTransferData(DataFlavor flavor)
      throws UnsupportedFlavorException, IOException {
    if (isDataFlavorSupported(flavor)) {
      return (Object) path;
    } else {
      throw new UnsupportedFlavorException(flavor);


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