Multiple DnD in JTreeTable

Question

Hi Folks--
two weeks ago I started to implement Drag and Drop for my wonderful TreeTableComponent, that is based on a JTreeTable described in an article by sun. It didn't took me long to figure that dnd is not the easiest thing to do for a JTreeTable. So I browsed this forum and found many other people who have or had the same problem. Since the given answers didn't help me so much, I thought it would be good to publish my implementation here:
After two weeks I managed to implement dnd in the right way (as I belive). Here's my solution.
1. disable internal dnd function by setDragEnabled(false)
2. set your own transfer handler that manages dnd for you (derive from TransferHander or simply create an instance of TransferHandler)
3. add a mouse listener and a mouse motion listener to your treeTable to tell the transfer handler to start the drag
4. revert order of mouse listener that you mouse listener is called first -> this is importent to keep selection on all previously selected nodes (prevents internal mouse handler of tree changing selection to the node you just clicked onto)
5. set selection mode of table and tree to make multiple selection possible to the user
add this where you init the table:
('table' is instance of a JTreeTable derivative)
        //disable internal dnd functionality, because we need our own implementation
        table.setDragEnabled(false); 
       //attach transfer handler
        table.setTransferHandler(createTransferHandler());
        //since we have a transfer handler, we just need to attach mouse listeners
        //to initiate the drag inside of the transfer handler
        DnDMouseAdapter dndMouseAdapter = new DnDMouseAdapter();
        table.addMouseListener(dndMouseAdapter);
        table.addMouseMotionListener(new DnDMouseMotionAdapter());
        //revert MouseListeners order so that our MouseListener is called first
        //this is important to give drag n drop first priority and prevent the
        //internal mouse handler of tableUI changing the selection.
        MouseListener[] mls = table.getMouseListeners();
        for (int i = 0; i < mls.length; i++) {
            if (mls[i] != dndMouseAdapter) {
                table.removeMouseListener(mls);
table.addMouseListener(mls[i]);
//set multiple selection
table.getSelectionModel().setSelectionMode(getSelectionMode());
//set selection mode for tree
final JTree tree = getTreeTable().getTree();
tree.getSelectionModel().setSelectionMode(TreeSelectionModel.DISCONTIGUOUS_TREE_SELECTION);
The idea for the mouse listeners I got from sun's swing tutorial. So here's the code for dndMouseAdapter and dndMouseMotionAdapter:
  class DnDMouseAdapter extends MouseAdapter {
        public void mousePressed(MouseEvent e) {
            firstMouseEvent = e;
            e.consume();
        public void mouseReleased(MouseEvent e) {
            firstMouseEvent = null;
    class DnDMouseMotionAdapter extends MouseMotionAdapter {
        //define diplacement of five pixel for as drag
        private static final int PIXEL_DISPLACEMENT = 5;
        public void mouseDragged(MouseEvent e) {
            if (firstMouseEvent != null) {
                e.consume();
                //if the user holds down the control key -> COPY, otherwise MOVE
                int ctrlMask = InputEvent.CTRL_DOWN_MASK;
                int action = ((e.getModifiersEx() & ctrlMask) == ctrlMask) ? TransferHandler.COPY : TransferHandler.MOVE;
                int dx = Math.abs(e.getX() - firstMouseEvent.getX());
                int dy = Math.abs(e.getY() - firstMouseEvent.getY());
                //define a displacement of at least some pixel as a drag
                if (dx > DnDMouseMotionAdapter.PIXEL_DISPLACEMENT || dy > DnDMouseMotionAdapter.PIXEL_DISPLACEMENT) {
                    //starting to drag...
                    JComponent c = (JComponent) e.getSource();
                    TransferHandler handler = c.getTransferHandler();
                    //tell transfer handler to start drag
                    handler.exportAsDrag(c, firstMouseEvent, action);
                    //reset first mouse event for the next time
                    firstMouseEvent = null;
    }I hope that helps! ;-)
Any comment is apprechiated!
Kind regards,
Patrick

Answer 1

I'm absolutetly devastated!!
I spent hours looking for advice on a treetable component after someone mentioned the idea not too long ago, in another thread might I add.
And I just spent the last 2 damn weeks implementing myy own. I feel heart broken! JTreeTable v1 was even very similar tomy first bash...but I gave on using the JTree as the renderer as it just looked lame... the way I did it anyway.
So just today I finished my own impl, with a new JComponent derivative soley for the rendering of the tree-like column.
Any clue as to when they intend to make it a standard JFC Swing component.
Bloody marvelous! So annoyed as it was a serious road-block to my current project! And asmuch as it was fun, I didn't choose to do for fun. AAAAAAARRRGGH!!
ps. congratulations, if you feel at all like how I felt half an hour ago, you must be very chuffed.