Tree: Drag and Drop : Tree « Swing JFC « Java

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Java » Swing JFC » Tree 

Tree: Drag and Drop
Tree: Drag and Drop
Definitive Guide to Swing for Java 2, Second Edition
By John Zukowski     
ISBN: 1-893115-78-X
Publisher: APress

import java.awt.BorderLayout;
import java.awt.Insets;
import java.awt.Point;
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.DragSource;
import java.awt.dnd.DragSourceContext;
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.util.Iterator;
import java.util.List;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JSplitPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeModel;
import javax.swing.tree.TreeNode;
import javax.swing.tree.TreePath;

public class TreeTester {
  public static void main(String args[]) {
    JFrame f = new JFrame("Tree Dragging Tester");
    DndTree tree1 = new DndTree();
    JScrollPane leftPane = new JScrollPane(tree1);
    DndTree tree2 = new DndTree();
    JScrollPane rightPane = new JScrollPane(tree2);
    JSplitPane splitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,
        leftPane, rightPane);
    f.getContentPane().add(splitPane, BorderLayout.CENTER);

class DndTree extends JTree implements Autoscroll {

  private Insets insets;

  private int top = 0, bottom = 0, topRow = 0, bottomRow = 0;

  public DndTree() {
    DragSource dragSource = DragSource.getDefaultDragSource();
            new TreeDragGestureListener());
    DropTarget dropTarget = new DropTarget(this,
        new TreeDropTargetListener());

  public DndTree(TreeModel model) {
    DragSource dragSource = DragSource.getDefaultDragSource();
            new TreeDragGestureListener());
    DropTarget dropTarget = new DropTarget(this,
        new TreeDropTargetListener());

  public Insets getAutoscrollInsets() {
    return insets;

  public void autoscroll(Point p) {
    // Only support up/down scrolling
    top = Math.abs(getLocation().y10;
    bottom = top + getParent().getHeight() 20;
    int next;
    if (p.y < top) {
      next = topRow--;
    else if (p.y > bottom) {
      next = bottomRow++;

  private static class TreeDragGestureListener implements DragGestureListener {
    public void dragGestureRecognized(DragGestureEvent dragGestureEvent) {
      // Can only drag leafs
      JTree tree = (JTreedragGestureEvent.getComponent();
      TreePath path = tree.getSelectionPath();
      if (path == null) {
        // Nothing selected, nothing to drag
        System.out.println("Nothing selected - beep");
      else {
        DefaultMutableTreeNode selection = (DefaultMutableTreeNodepath
        if (selection.isLeaf()) {
          TransferableTreeNode node = new TransferableTreeNode(
              node, new MyDragSourceListener());
        else {
          System.out.println("Not a leaf - beep");

  private class TreeDropTargetListener implements DropTargetListener {

    public void dragEnter(DropTargetDragEvent dropTargetDragEvent) {
      // Setup positioning info for auto-scrolling
      top = Math.abs(getLocation().y);
      bottom = top + getParent().getHeight();
      topRow = getClosestRowForLocation(0, top);
      bottomRow = getClosestRowForLocation(0, bottom);
      insets = new Insets(top + 100, bottom - 10, getWidth());

    public void dragExit(DropTargetEvent dropTargetEvent) {

    public void dragOver(DropTargetDragEvent dropTargetDragEvent) {

    public void dropActionChanged(DropTargetDragEvent dropTargetDragEvent) {

    public synchronized void drop(DropTargetDropEvent dropTargetDropEvent) {
      // Only support dropping over nodes that aren't leafs

      Point location = dropTargetDropEvent.getLocation();
      TreePath path = getPathForLocation(location.x, location.y);
      Object node = path.getLastPathComponent();
      if ((node != null&& (node instanceof TreeNode)
          && (!((TreeNodenode).isLeaf())) {
        try {
          Transferable tr = dropTargetDropEvent.getTransferable();
          if (tr
              .isDataFlavorSupported(TransferableTreeNode.DEFAULT_MUTABLE_TREENODE_FLAVOR)) {
            Object userObject = tr
            addElement(path, userObject);
          else if (tr
              .isDataFlavorSupported(DataFlavor.stringFlavor)) {
            String string = (Stringtr
            addElement(path, string);
          else if (tr
              .isDataFlavorSupported(DataFlavor.plainTextFlavor)) {
            Object stream = tr
            if (stream instanceof InputStream) {
              InputStreamReader isr = new InputStreamReader(
              BufferedReader reader = new BufferedReader(isr);
              String line;
              while ((line = reader.readLine()) != null) {
                addElement(path, line);
            else if (stream instanceof Reader) {
              BufferedReader reader = new BufferedReader(
              String line;
              while ((line = reader.readLine()) != null) {
                addElement(path, line);
            else {
              System.err.println("Unknown type: "
                  + stream.getClass());
          else if (tr
              .isDataFlavorSupported(DataFlavor.javaFileListFlavor)) {
            List fileList = (Listtr
            Iterator iterator = fileList.iterator();
            while (iterator.hasNext()) {
              File file = (;
              addElement(path, file.toURL());
          else {
        catch (IOException io) {
        catch (UnsupportedFlavorException ufe) {
      else {
        System.out.println("Can't drop on a leaf");

    private void addElement(TreePath path, Object element) {
      DefaultMutableTreeNode parent = (DefaultMutableTreeNodepath
      DefaultMutableTreeNode node = new DefaultMutableTreeNode(element);
      System.out.println("Added: " + node + " to " + parent);
      DefaultTreeModel model = (DefaultTreeModel) (DndTree.this
      model.insertNodeInto(node, parent, parent.getChildCount());

  private static class MyDragSourceListener implements DragSourceListener {
    public void dragDropEnd(DragSourceDropEvent dragSourceDropEvent) {
      if (dragSourceDropEvent.getDropSuccess()) {
        int dropAction = dragSourceDropEvent.getDropAction();
        if (dropAction == DnDConstants.ACTION_MOVE) {
          System.out.println("MOVE: remove node");

    public void dragEnter(DragSourceDragEvent dragSourceDragEvent) {
      DragSourceContext context = dragSourceDragEvent
      int dropAction = dragSourceDragEvent.getDropAction();
      if ((dropAction & DnDConstants.ACTION_COPY!= 0) {
      else if ((dropAction & DnDConstants.ACTION_MOVE!= 0) {
      else {

    public void dragExit(DragSourceEvent dragSourceEvent) {

    public void dragOver(DragSourceDragEvent dragSourceDragEvent) {

    public void dropActionChanged(DragSourceDragEvent dragSourceDragEvent) {

class TransferableTreeNode extends DefaultMutableTreeNode implements
    Transferable {
  final static int TREE = 0;

  final static int STRING = 1;

  final static int PLAIN_TEXT = 1;

  final public static DataFlavor DEFAULT_MUTABLE_TREENODE_FLAVOR = new DataFlavor(
      DefaultMutableTreeNode.class, "Default Mutable Tree Node");

  static DataFlavor flavors[] DEFAULT_MUTABLE_TREENODE_FLAVOR,
      DataFlavor.stringFlavor, DataFlavor.plainTextFlavor };

  private DefaultMutableTreeNode data;

  public TransferableTreeNode(DefaultMutableTreeNode data) { = data;

  public DataFlavor[] getTransferDataFlavors() {
    return flavors;

  public Object getTransferData(DataFlavor flavor)
      throws UnsupportedFlavorException, IOException {
    Object returnObject;
    if (flavor.equals(flavors[TREE])) {
      Object userObject = data.getUserObject();
      if (userObject == null) {
        returnObject = data;
      else {
        returnObject = userObject;
    else if (flavor.equals(flavors[STRING])) {
      Object userObject = data.getUserObject();
      if (userObject == null) {
        returnObject = data.toString();
      else {
        returnObject = userObject.toString();
    else if (flavor.equals(flavors[PLAIN_TEXT])) {
      Object userObject = data.getUserObject();
      String string;
      if (userObject == null) {
        string = data.toString();
      else {
        string = userObject.toString();
      returnObject = new ByteArrayInputStream(string.getBytes("Unicode"));
    else {
      throw new UnsupportedFlavorException(flavor);
    return returnObject;

  public boolean isDataFlavorSupported(DataFlavor flavor) {
    boolean returnValue = false;
    for (int i = 0, n = flavors.length; i < n; i++) {
      if (flavor.equals(flavors[i])) {
        returnValue = true;
    return returnValue;


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