DND from JTree to JTable

[Yahya Elyasse]

Hi guys,

It seems JTree DnD support is a quit difficult feature to implement of all swing components.
I'm writing an application in which I have a JTree structure representing the file system of user machine and another JTable component at the right.

I want to be able to drag files nodes from left JTree to right JTable.

I would appreciate a lot if someone share with me some source code examples for this functionality.
can someone post some basic java code to get me started or point me to some web resource discussing this feature?

thanks much.

[Craig Wood]

import java.awt.*;
import java.awt.event.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import java.io.*;
import javax.swing.*;
import javax.swing.tree.*;
 
public class TreeDrag {
    JTree tree;
    JTable table;
    final static String TARGET_EXT = "java";
 
    private JPanel getContent() {
        JPanel panel = new JPanel(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.weightx = 1.0;
        gbc.weighty = 1.0;
        gbc.fill = gbc.BOTH;
        gbc.insets.right = 2;
        panel.add(getTreeComponent(), gbc);
        gbc.insets.left = 2;
        panel.add(getTableComponent(), gbc);
        return panel;
    }
 
    private JScrollPane getTreeComponent() {
        tree = new DragTree(new DefaultTreeModel(null));
        Thread thread = new Thread(new Runnable() {
            public void run() {
                DefaultMutableTreeNode node = getTreeData();
                DefaultTreeModel model = (DefaultTreeModel)tree.getModel();
                model.setRoot(node);
            }
        });
        thread.setPriority(Thread.NORM_PRIORITY);
        thread.start();
        return new JScrollPane(tree);
    }
 
    private DefaultMutableTreeNode getTreeData() {
        String path = "c:/jexp";
        File folder = new File(path);
        DefaultMutableTreeNode root = 
            new DefaultMutableTreeNode(new FileStore(null, path));
        createNodesFor(folder, root);
        return root;
    }
 
    private void createNodesFor(File folder, DefaultMutableTreeNode root) {
        folder.setReadOnly();
        File[] files = folder.listFiles(filter);
        DefaultMutableTreeNode[] nodes = new DefaultMutableTreeNode[files.length];
        for(int j = 0; j < files.length; j++) {
            String s = files[j].getName();
            int dot = s.lastIndexOf(".");
            if(dot != -1)
                s = s.substring(0, dot);
            if(files[j].isDirectory()) {
                DefaultMutableTreeNode subNode =
                    new DefaultMutableTreeNode(new FileStore(null, s));
                createNodesFor(files[j], subNode);
                if(subNode.getChildCount() == 0) {
                    s = "no " + TARGET_EXT + " files";
                    DefaultMutableTreeNode n =
                        new DefaultMutableTreeNode(new FileStore(null, s));
                    subNode.add(n);
                }
                root.insert(subNode, j);
            } else {
                nodes[j] = new DefaultMutableTreeNode(new FileStore(files[j], s));
                root.insert(nodes[j], j);
            }
        }
    }
 
    private JScrollPane getTableComponent() {
        table = new DropTable(8, 2);
        return new JScrollPane(table);
    }
 
    public static void main(String[] args) {
        TreeDrag test = new TreeDrag();
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(test.getContent());
        f.setSize(500,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
 
    private FileFilter filter = new FileFilter() {
        public boolean accept(File file) {
            String ext = getExtension(file);
            if(ext.equals(TARGET_EXT) || file.isDirectory())
                return true;
            return false;
        }
 
        private String getExtension(File file) {
            String s = file.getName();
            int dot = s.lastIndexOf(".");
            return s.substring(dot+1);
        }
    };
}
 
class FileStore {
    File file;
    String fileName;
 
    public FileStore(File file, String name) {
        this.file = file;
        fileName = name;
    }
 
    public String toString() { return fileName; }
}
 
class FileStoreTransferable implements Transferable,
                                       ClipboardOwner {
    private FileStore fileStore;
    public static final DataFlavor[] flavors = new DataFlavor[1];
    public static DataFlavor fileStoreFlavor = null;
    static {
        try {
            fileStoreFlavor = new DataFlavor(FileStore.class,
                                             "FileStore");
            flavors[0] = fileStoreFlavor;
        } catch(Exception e) {
        }
    }
 
    public FileStoreTransferable(FileStore fileStore) {
        this.fileStore = fileStore;
    }
 
    public DataFlavor[] getTransferDataFlavors() {
        return flavors;
    }
 
    public boolean isDataFlavorSupported(DataFlavor flavor) {
        for(int j = 0; j < flavors.length; j++) {
            if(fileStoreFlavor == flavors[j])
                return true;
        }
        return false;
    }
 
    public Object getTransferData(DataFlavor flavor)
                                    throws UnsupportedFlavorException,
                                           IOException {
        if(fileStoreFlavor != flavor)
            throw new UnsupportedFlavorException(flavor);
        return fileStore;
    }
 
    public String toString() { return "FileStoreTransferable"; }
 
    public void lostOwnership(Clipboard clipboard, Transferable t) {
        System.out.printf("FileStoreTransferable lost ownership of %s data: %s%n",
                           clipboard.getName(), t);
    }
}

import java.awt.*;
import java.awt.event.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.tree.*;
 
public class DragTree extends JTree  {
    DragSource dragSource;
    DragSourceMonitor dragSourceMonitor;
    DragGestureMonitor dragGestureMonitor;
    int dragAction = DnDConstants.ACTION_MOVE;
 
    public DragTree(DefaultTreeModel model) {
        super(model);
        dragSource = DragSource.getDefaultDragSource();
        dragSourceMonitor = new DragSourceMonitor();
        dragGestureMonitor = new DragGestureMonitor();
        DragGestureRecognizer dgr =
            dragSource.createDefaultDragGestureRecognizer(this, dragAction,
                                                          dragGestureMonitor);
        // Disable popupTrigger for dragSource.
        dgr.setSourceActions(dgr.getSourceActions() & ~InputEvent.BUTTON3_MASK);
    }
 
    class DragGestureMonitor implements DragGestureListener {
        public void dragGestureRecognized(DragGestureEvent e) {
            // If a node has been selected get a reference to it.
            Point p = e.getDragOrigin();
            TreePath path = getPathForLocation(p.x, p.y);
            DefaultMutableTreeNode node = null;
            if(path != null)
                node = (DefaultMutableTreeNode)path.getLastPathComponent();
            if(node != null) {
                System.out.printf("node = %s%n", node);
                // If node is being edited, stop edit.
                if(isEditing()) {
                    TreePath editPath = getEditingPath();
                    DefaultMutableTreeNode editNode =
                        (DefaultMutableTreeNode)editPath.getLastPathComponent();
                    if(node == editNode)
                        stopEditing();
                }
                // Allow dragging for only leaf nodes.
                if(e.getDragAction() == dragAction && node.isLeaf()) {
                    FileStore fileStore = (FileStore)node.getUserObject();
                    Transferable transferable = new FileStoreTransferable(fileStore);
                    Cursor cursor = DragSource.DefaultCopyNoDrop;
                    cursor = DragSource.DefaultMoveNoDrop;
                    dragSource.startDrag(e, cursor, transferable, dragSourceMonitor);
                    //e.startDrag(cursor, transferable, dragSourceMonitor);
                }
            }
        }
    }
 
    class DragSourceMonitor implements DragSourceListener  {
 
        public void dragDropEnd(DragSourceDropEvent e) {
            if(!e.getDropSuccess()) {
                System.out.println("drop failed");
                return;
            }
            //System.out.println("DragSourceMonitor dragDropEnd");
            DefaultMutableTreeNode node =
                (DefaultMutableTreeNode)getLastSelectedPathComponent();
            DefaultTreeModel model = (DefaultTreeModel)getModel();
            model.removeNodeFromParent(node);
        }
 
        public void dragEnter(DragSourceDragEvent e) {
            //System.out.println("DragSourceMonitor dragSource");
            DragSourceContext context = e.getDragSourceContext();
            Cursor cursor = DragSource.DefaultMoveNoDrop;
            if((e.getDropAction() & dragAction) != 0)
                cursor = DragSource.DefaultMoveDrop;
            context.setCursor(cursor);
        }
 
        public void dragExit(DragSourceEvent e) {
            //System.out.println("DragSourceMonitor dragSource");
            DragSourceContext context = e.getDragSourceContext();
            context.setCursor(DragSource.DefaultMoveNoDrop);
        }
 
        public void dragOver(DragSourceDragEvent e) {
            //System.out.println("DragSourceMonitor dragOver");
        }
 
        public void dropActionChanged(DragSourceDragEvent e) {
            DragSourceContext context = e.getDragSourceContext();
            context.setCursor(DragSource.DefaultMoveNoDrop);
        }
    }
}

import java.awt.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import java.io.IOException;
import javax.swing.*;
import javax.swing.table.*;
 
public class DropTable extends JTable {
    DropTarget dropTarget;
    DropTargetListener dropMonitor;
    int dropActions = DnDConstants.ACTION_MOVE;
 
    public DropTable(int rows, int cols) {
        super(rows, cols);
        setRowSelectionAllowed(true);
        setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        dropMonitor = new DropTargetMonitor();
        dropTarget = new DropTarget(this, dropActions, dropMonitor, true);
    }
 
    private void addData(FileStore fileStore, int row) {
        // Find next empty row.
        int emptyRow = getNextEmptyRow(row);
        if(emptyRow != -1) {
            shiftValuesDown(row, emptyRow);
        } else {
            row = getRowCount();
            DefaultTableModel model = (DefaultTableModel)getModel();
            model.setRowCount(getRowCount()+1);
        }
        setValueAt(fileStore.fileName, row, 0);
        setValueAt(fileStore.file, row, 1);
    }
 
    private int getNextEmptyRow(int start) {
        for(int j = start; j < getRowCount(); j++) {
            if(getValueAt(j, 0) == null)
                return j;
        }
        return -1;
    }
 
    private void shiftValuesDown(int start, int end) {
        for(int j = end; j > start; j--) {
            setValueAt(getValueAt(j-1, 0), j, 0);
            setValueAt(getValueAt(j-1, 1), j, 1);
        }
    }
 
    class DropTargetMonitor implements DropTargetListener {
        public void dragEnter(DropTargetDragEvent e) {
            //System.out.println("DropTargetMonitor dragEnter");
            if(isDragOK(e))
                e.acceptDrag(e.getDropAction());
            else
                e.rejectDrag();
        }
 
        public void dragExit(DropTargetEvent e) {
            //System.out.println("DropTargetMonitor dragExit");
            clearSelection();
        }
 
        public void dragOver(DropTargetDragEvent e) {
            //System.out.println("DropTargetMonitor dragOver");
            Point loc = e.getLocation();
            int row = rowAtPoint(loc);
            setRowSelectionInterval(row, row);
            if(isDragOK(e))
                e.acceptDrag(e.getDropAction());
            else
                e.rejectDrag();
        }
 
        public void drop(DropTargetDropEvent e) {
            try {
                Transferable t = e.getTransferable();
                if(!t.isDataFlavorSupported(FileStoreTransferable.fileStoreFlavor))
                    e.rejectDrop();
                FileStore data =
                    (FileStore)t.getTransferData(FileStoreTransferable.fileStoreFlavor);
                Point loc = e.getLocation();
                int row = rowAtPoint(loc);
                if(getValueAt(row, 0) == null ) {
                    setValueAt(data.fileName, row, 0);
                    setValueAt(data.file, row, 1);
                } else {
                    addData(data, row);
                }
                e.getDropTargetContext().dropComplete(true);
            } catch(IOException ioe) {
                e.rejectDrop();
            } catch(UnsupportedFlavorException ufe) {
                e.rejectDrop();
            }
        }
 
        public void dropActionChanged(DropTargetDragEvent e) {
            if(isDragOK(e))
                e.acceptDrag(e.getDropAction());
            else
                e.rejectDrag();
        }
 
        private boolean isDragOK(DropTargetDragEvent e) {
            if(e.isDataFlavorSupported(FileStoreTransferable.fileStoreFlavor) &&
                   e.getDropAction() == dropActions)
                return true;
            return false;
        }
    }
}

[Brian Cole]

I haven't looked closely at Mr. Wood's code, but if you can presume jdk 1.4 or better, I think it would probably be easier to use the TransferHandler class.

JTree myTree = new JTree(...);
JTable myTable = new JTable(...);
myTree.setTransferHandler(...); // pass a handler for the drag-out
myTable.setTransferHandler(...); // pass a handler for the drop-into

It's that easy. Ok, not really because you have to actually write the TransferHandlers, but it's not so bad. It's easier to comprehend than the DragGesture/DropTarget stuff, and Sun does provide some examples.

a few notes, because I'm oh so helpful:

1) If you can presume 1.6 or better, you probably want to call myTable.setDropMode() for better drop feedback.

2) If it might be run on 1.5, you probably want to set the sun.swing.enableImprovedDragGesture system property.
[edit: I've had trouble with this on Macs, in that it made dropping impossible. So either set sun.swing.enableImprovedDragGesture only on non-Macs, or test well.]

3) If you want to convey Java objects within the same JVM and you don't want your objects to be silently serialized and deserialized, set the MIME type of your Transferable to something like DataFlavor.javaJVMLocalObjectMimeType+";class=the.fully.qualified.ClassName". The Sun tutorial linked above mentions this, but it's easy to miss.
[ December 14, 2006: Message edited by: Brian Cole ]

[Yahya Elyasse]

Hi,
thank you for interesting replies.

the code posted by Mr.craig is excellent and works. but when i tried integrating it into my complex TreeTable component i was frustrated by a DnD problem on Linux platform.the code works on win & Mac but fails on Linux with an error:
cannot find top level for source drag component.

I finally opted for using TransferHandler class and succeeded at last to get it work on Linux. thanks for pointing out the TransferHandler class.

[Yahya Elyasse]

Hi guys,
I'm still having problems with JTree DnD ...
I wrote a drag listener class for my JTree and the code runs well on windows.

    
public class TreeDragSource 
implements DragSourceListener, DragGestureListener {
 
DragSource source;
DragGestureRecognizer recognizer;
TransferableTreeNode transferable;
 
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)) {
  
   return;
 }
 
 transferable = new TransferableTreeNode(path);
 
 // If you support dropping the node anywhere, you should probably
 // start with a valid move cursor:
 util.Trace.log(
"start drag file [ "+((FileNode) path.getLastPathComponent()).getFile().getName()+" ]");
 source.startDrag(dge, DragSource.DefaultMoveDrop, transferable, this);
// dge.startDrag( 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) { 
 
}
public void dragDropEnd(DragSourceDropEvent dsde) {
 /*
  * to support move or copy, we have to check which occurred:
  */
 
 if (dsde.getDropSuccess() &&
     (dsde.getDropAction() == DnDConstants.ACTION_MOVE)) {
 
 util.Trace.log(
"drop success of file [ "+((FileNode) transferable.path.getLastPathComponent()).getFile().getName()+" ]");
 
 }
 
 
}  
} 

however when i tested on Linux i got this exception:

Exception in thread "AWT-EventQueue-1" java.awt.dnd.InvalidDnDOperationException: Cannot find top-level for the drag source component
at sun.awt.X11.XDragSourceContextPeer.startDrag(XDragSourceContextPeer.java:105)
at sun.awt.dnd.SunDragSourceContextPeer.startDrag(SunDragSourceContextPeer.java:111)
at java.awt.dnd.DragSource.startDrag(DragSource.java:306)
at java.awt.dnd.DragSource.startDrag(DragSource.java:403)
at treetable.TreeDragSource.dragGestureRecognized(TreeDragSource.java:67)
at java.awt.dnd.DragGestureRecognizer.fireDragGestureRecognized(DragGestureRecognizer.java:339)
at sun.awt.X11.XMouseDragGestureRecognizer.mouseDragged(XMouseDragGestureRecognizer.java:202)
at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:262)
at java.awt.Component.processMouseMotionEvent(Component.java:5536)
at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:3144)
at java.awt.Component.processEvent(Component.java:5257)
at java.awt.Container.processEvent(Container.java:1966)
at java.awt.Component.dispatchEventImpl(Component.java:3955)
at java.awt.Container.dispatchEventImpl(Container.java:2024)
at java.awt.Component.dispatchEvent(Component.java:3803)
at javax.swing.plaf.basic.BasicTableUI$Handler.repostEvent(BasicTableUI.java:900)
at javax.swing.plaf.basic.BasicTableUI$Handler.mouseDraggedImpl(BasicTableUI.java:1044)
at javax.swing.plaf.basic.BasicTableUI$Handler.mouseDragged(BasicTableUI.java:1040)
at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:262)
at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:261)
at java.awt.Component.processMouseMotionEvent(Component.java:5536)
at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:3144)
at java.awt.Component.processEvent(Component.java:5257)
at java.awt.Container.processEvent(Container.java:1966)
at java.awt.Component.dispatchEventImpl(Component.java:3955)
at java.awt.Container.dispatchEventImpl(Container.java:2024)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3909)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822)
at java.awt.Container.dispatchEventImpl(Container.java:2010)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
 

any Ideas where the problem is ?

thanks for helping.

[Craig Wood]

I don't have access to linux but I did a little snooping around for you.
Instead of creating a new DragSource you could try DragSource.getDefaultDragSource to see
if it gives a more useful platform–specific reference. The next–to–last paragraph in the
comments section of the DragSource api offers two possibilities for this exception.
Some possibly relevant JDK Bug research results:
For drag&drop:
JTree nodes which implement Drag&Drop and Mouse Event act incorrect
Dnd with JTrees does not work on linux/motif
For dragndrop:
JWindow on Linux can't accept a drop
XDnD support
The Evaluation section of the first bug report in the list above suggests that the AWT
drag_n_drop classes do not work so well with Swing components, especially with respect to
drag gesture recognition. Brian Cole's recommendation to use TransferHandlers may be the
better way to go.

[Yahya Elyasse]

Thank you Mr Craig for pointing out these DnD bugs.

I actually wrote a TransferHandler and it seems it worked well on Linux. but sometime I'm having some weired behavior of the JTree : when i select a Node & start dragging ; the JTree node disappear or change position & goes up ..brief the Jtree nodes get messed up..I'm guessing it's an issue with mouse listener , or may be TreeSelectionListener or smth else..I don't know where the problem is..here is my TransferHandler:

import java.awt.datatransfer.Transferable;
 
import java.awt.event.MouseEvent;
 
import java.awt.event.MouseMotionListener;
 

 
import javax.swing.JComponent;
 
import javax.swing.JTree;
 
import javax.swing.TransferHandler;
 
import javax.swing.tree.TreePath;
 

 

 

 
public class JTreeTransferHandler extends TransferHandler {
 

 
protected Transferable createTransferable(JComponent c) {
 
return (exportNode(c));
 
}
 

 
public int getSourceActions(JComponent c) {
 
return COPY_OR_MOVE;
 
}
 

 
protected Transferable exportNode(JComponent c) {
 
Transferable tr = null;
 
if (c instanceof JTree) {
 

 
JTree tree = (JTree) c;
 

 
TreePath path = tree.getSelectionPath();
 

 
if ((path == null) || (path.getPathCount() <= 1)) {
 
// We can't move the root node or an empty selection
 
// System.out.println(path);
 
return null;
 
}
 
// System.out.println(path);
 
tr = new TransferableTreeNode(path);
 

 
}
 
return tr;
 

 
}
 

 
class DragHandler implements MouseMotionListener {
 

 
MouseEvent firstMouseEvent;
 

 
public void mousePressed(MouseEvent e) {
 
firstMouseEvent = e;
 
e.consume();
 
}
 

 
public void mouseDragged(MouseEvent e) {
 
if (firstMouseEvent != null) {
 
e.consume();
 
int dx = Math.abs(e.getX() - firstMouseEvent.getX());
 
int dy = Math.abs(e.getY() - firstMouseEvent.getY());
 
// Arbitrarily define a 5-pixel shift as the
 
// official beginning of a drag.
 
if (dx > 5 || dy > 5) {
 

 
JComponent c = ((JTree) e.getSource());
 

 
JTreeTransferHandler th = (JTreeTransferHandler) c
 
.getTransferHandler();
 
Transferable t = th.createTransferable(c);
 

 
th.exportDone(c, t, COPY_OR_MOVE);
 
firstMouseEvent = null;
 
}
 
}
 
}
 

 
public void mouseReleased(MouseEvent e) {
 
firstMouseEvent = null;
 
}
 

 
public void mouseMoved(MouseEvent e) {
 
}
 

 
}
 

 
}
 
    

can you please help me write a working & cross platform TransferHandler of my JTree ? that would be very nice.

thanks.

[Craig Wood]

sometime I'm having some weired behavior of the JTree
This is likely because of the added DragHandler conflicting with the default drag_and_drop
support that is built into JTree. To get an idea about this look at the tutorial page
given by Brian Cole: How to Use Drag and Drop and Data Transfer, in the
Data Transfer Support table at the top of the page.
Notice that the default support for JTree is Drag_Copy, the same as for both JColorChooser
and JFileChooser. In the examples given for these components, DragColorDemo in the section
Importing a New Flavor: Color
and DragFileDemo in the section Importing a New Flavor: Files,
there was no need for a MouseMotionListener because Swing does this for us when we setDragEnabled(true)
on the component. So the extra DragHandler in your JTreeTransferHandler class is fighting
with Swing.
The extra MouseMotionListener handler is required for components that do not have the
default support as shown in the Data Transfer Support table.
Here is an implementation using TransferHandlers where the FileStore class remains
unchanged nad the only change in the FileStoreTransferable class is

        try {
            String fileStoreType = DataFlavor.javaJVMLocalObjectMimeType +
                                   ";class=FileStore";
            fileStoreFlavor = new DataFlavor(fileStoreType);
            flavors[0] = fileStoreFlavor;

as recommended by Brian Cole to eliminate the need for serialization.

import java.awt.*;
import java.awt.event.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import java.io.*;
import javax.swing.*;
import javax.swing.tree.*;
 
public class TreeToTable {
    JTree tree;
    JTable table;
    final static String TARGET_EXT = "java";
 
    private JPanel getContent() {
        JPanel panel = new JPanel(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.weightx = 1.0;
        gbc.weighty = 1.0;
        gbc.fill = gbc.BOTH;
        gbc.insets.right = 2;
        panel.add(getTreeComponent(), gbc);
        gbc.insets.left = 2;
        panel.add(getTableComponent(), gbc);
        return panel;
    }
 
    private JScrollPane getTreeComponent() {
        tree = new JTree(new DefaultTreeModel(null));
        tree.setDragEnabled(true);
        tree.setTransferHandler(new TreeTransferHandler());
        Thread thread = new Thread(new Runnable() {
            public void run() {
                DefaultMutableTreeNode node = getTreeData();
                DefaultTreeModel model = (DefaultTreeModel)tree.getModel();
                model.setRoot(node);
            }
        });
        thread.setPriority(Thread.NORM_PRIORITY);
        thread.start();
        return new JScrollPane(tree);
    }
 
    private DefaultMutableTreeNode getTreeData() {
        String path = "c:/jexp";
        File folder = new File(path);
        DefaultMutableTreeNode root = 
            new DefaultMutableTreeNode(new FileStore(null, path));
        createNodesFor(folder, root);
        return root;
    }
 
    private void createNodesFor(File folder, DefaultMutableTreeNode root) {
        folder.setReadOnly();
        File[] files = folder.listFiles(filter);
        DefaultMutableTreeNode[] nodes = new DefaultMutableTreeNode[files.length];
        for(int j = 0; j < files.length; j++) {
            String s = files[j].getName();
            int dot = s.lastIndexOf(".");
            if(dot != -1)
                s = s.substring(0, dot);
            if(files[j].isDirectory()) {
                DefaultMutableTreeNode subNode =
                    new DefaultMutableTreeNode(new FileStore(null, s));
                createNodesFor(files[j], subNode);
                if(subNode.getChildCount() == 0) {
                    s = "no " + TARGET_EXT + " files";
                    DefaultMutableTreeNode n =
                        new DefaultMutableTreeNode(new FileStore(null, s));
                    subNode.add(n);
                }
                root.insert(subNode, j);
            } else {
                nodes[j] = new DefaultMutableTreeNode(new FileStore(files[j], s));
                root.insert(nodes[j], j);
            }
        }
    }
 
    private JScrollPane getTableComponent() {
        table = new JTable(8, 2);
        table.setRowSelectionAllowed(true);
        table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        table.setTransferHandler(new TableTransferHandler());
        return new JScrollPane(table);
    }
 
    public static void main(String[] args) {
        TreeToTable test = new TreeToTable();
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(test.getContent());
        f.setSize(500,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
 
    private FileFilter filter = new FileFilter() {
        public boolean accept(File file) {
            String ext = getExtension(file);
            if(ext.equals(TARGET_EXT) || file.isDirectory())
                return true;
            return false;
        }
 
        private String getExtension(File file) {
            String s = file.getName();
            int dot = s.lastIndexOf(".");
            return s.substring(dot+1);
        }
    };
}
 
import java.awt.datatransfer.*;
import javax.swing.*;
import javax.swing.tree.*;
 
public class TreeTransferHandler extends TransferHandler {
    protected Transferable createTransferable(JComponent c) {
        JTree tree = (JTree)c;
        DefaultMutableTreeNode node =
            (DefaultMutableTreeNode)tree.getLastSelectedPathComponent();
        if(tree.isEditing()) {
            TreePath editPath = tree.getEditingPath();
            DefaultMutableTreeNode editNode =
                (DefaultMutableTreeNode)editPath.getLastPathComponent();
            if(node == editNode)
                tree.stopEditing();
        }
        FileStore fileStore = (FileStore)node.getUserObject();
        return new FileStoreTransferable(fileStore);
    }
 
    protected void exportDone(JComponent source, Transferable data, int action) {
        if(action == MOVE) {
            JTree tree = (JTree)source;
            DefaultMutableTreeNode node =
                (DefaultMutableTreeNode)tree.getLastSelectedPathComponent();
            DefaultTreeModel model = (DefaultTreeModel)tree.getModel();
            model.removeNodeFromParent(node);
        }
    }
 
    public int getSourceActions(JComponent c) {
        return COPY_OR_MOVE;
    }
}
 
import java.awt.datatransfer.*;
import java.io.IOException;
import javax.swing.*;
import javax.swing.table.DefaultTableModel;
 
public class TableTransferHandler extends TransferHandler {
    DataFlavor fileStoreFlavor = FileStoreTransferable.fileStoreFlavor;
 
    public boolean canImport(JComponent comp, DataFlavor[] flavors) {
        for (int j = 0; j < flavors.length; j++) {
            if (fileStoreFlavor.equals(flavors[j])) {
                return true;
            }
        }
        return false;
    }
 
    public boolean importData(JComponent comp, Transferable t) {
        if(canImport(comp, t.getTransferDataFlavors())) {
            FileStore data = null;
            try {
                data = (FileStore)t.getTransferData(fileStoreFlavor);
            } catch(UnsupportedFlavorException ufe) {
                System.out.println("unsupported flavor for " + fileStoreFlavor +
                                   ": " + ufe.getMessage());
                return false;
            } catch(IOException ioe) {
                System.out.println("io error: " + ioe.getMessage());
                return false;
            }
            JTable table = (JTable)comp;
            int row = table.getSelectedRow();
            if(table.getValueAt(row, 0) == null ) {
                table.setValueAt(data.fileName, row, 0);
                table.setValueAt(data.file, row, 1);
            } else {
                addData(table, data, row);
            }
            return true;
        }
        return false;
    }
 
    private void addData(JTable table, FileStore fileStore, int row) {
        // Find next empty row.
        int emptyRow = getNextEmptyRow(table, row);
        if(emptyRow != -1) {
            shiftValuesDown(table, row, emptyRow);
        } else {
            row = table.getRowCount();
            DefaultTableModel model = (DefaultTableModel)table.getModel();
            model.setRowCount(table.getRowCount()+1);
        }
        table.setValueAt(fileStore.fileName, row, 0);
        table.setValueAt(fileStore.file, row, 1);
    }
 
    private int getNextEmptyRow(JTable table, int start) {
        for(int j = start; j < table.getRowCount(); j++) {
            if(table.getValueAt(j, 0) == null)
                return j;
        }
        return -1;
    }
 
    private void shiftValuesDown(JTable table, int start, int end) {
        for(int j = end; j > start; j--) {
            table.setValueAt(table.getValueAt(j-1, 0), j, 0);
            table.setValueAt(table.getValueAt(j-1, 1), j, 1);
        }
    }
}

[Yahya Elyasse]

Mr. craig

Thanks for your precious help on this difficult DnD issue.
however I'm still having problems with my applet DnD code. actually I'm trying to implement DnD on a more complex component which is TreeTable. i think this might be probably the cause of all my troubles.

I was wondering if you are willing to look at my code and help me fix this TreeTable DnD issue. If you agree, I can upload all my code to a ftp url that i can send it to you in private message.

Let me know if you kindly accept to help me on this .
thanks.

[Craig Wood]

Okay.

[Yahya Elyasse]

Thank You Mr. Craig,
I sent you a private msg. let me know if you received the code.

thanks.