Java Swing - Dynamically change JList using TransferHandler

Question

I have a small Java swingui app where I display a JList and the user is able to cut, copy, paste and sort the list.

I use a custom TransferHandler to allow drag and drop on this Jlist. Here is the code in building the JList, it basically builds it from an ArrayList. "lstScripts" is the JList.

    ListTransferHandler lh = new ListTransferHandler();
...
    DefaultListModel listModelScripts = new DefaultListModel();
    for(Script s : scripts) {
        listModelScripts.addElement(s.getName());
    }
    this.lstScripts = new JList(listModelScripts);
    this.lstScripts.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
    this.lstScripts.addListSelectionListener(this);
    JScrollPane sp = new JScrollPane(this.lstScripts);
    sp.setPreferredSize(new Dimension(400,100));
    this.lstScripts.setDragEnabled(true);
    this.lstScripts.setTransferHandler(lh);
    this.lstScripts.setDropMode(DropMode.ON_OR_INSERT);
    setMappings(this.lstScripts);
...

On my custom TransferHandler class, I've got the importData routine working so that it handles the copy/paste/cut/sort.

public boolean importData(TransferHandler.TransferSupport info) {
    String scriptname = null; // The script name on the list

    //If we can't handle the import, bail now.
    if (!canImport(info)) {
        return false;
    }

    JList list = (JList)info.getComponent();
    DefaultListModel model = (DefaultListModel)list.getModel();
    //Fetch the scriptname -- bail if this fails
    try {
        scriptname = (String)info.getTransferable().getTransferData(DataFlavor.stringFlavor);
    } catch (UnsupportedFlavorException ufe) {
        System.out.println("importData: unsupported data flavor");
        return false;
    } catch (IOException ioe) {
        System.out.println("importData: I/O exception");
        return false;
    }

    if (info.isDrop()) { //This is a drop
        JList.DropLocation dl = (JList.DropLocation)info.getDropLocation();
        int index = dl.getIndex();
        model.add(index, scriptname);
        return true;
    } else { //This is a paste
        int index = list.getSelectedIndex();
        // if there is a valid selection,
        // insert scriptname after the selection
        if (index >= 0) {
            model.add(list.getSelectedIndex()+1, scriptname);
        // else append to the end of the list
        } else {
            model.addElement(scriptname);
        }
        return true;
    }
}

So up to here, everything works fine as far as the GUI. But my problem is I need the original JList "lstScripts" to be automatically updated with the user GUI changes. For example, if the user cuts or reorders the list, I want it to show on in "lstScripts".

I'm not seeing how to make this connection between the TransferHandler and original GUI controller where "lstScripts" resides.

You have access to the `ListModel`? If you really have to you, could also pass a controller to the `ListTransferHandler`... — MadProgrammer, Aug 07 '13 at 00:21
unrelated: [don't use setXXSize, ever](http://stackoverflow.com/a/7229519/203657) — kleopatra, Aug 07 '13 at 08:32
I don't understand the question: you are modifying the model, so updates simply happens - or do you have two lists? — kleopatra, Aug 07 '13 at 08:35

score 1 · Accepted Answer · answered Aug 07 '13 at 17:39

@kleopatra - you helped me! sorry I didnt understand how the model was working.

So in the controller, I create the "lstScripts" JList and add it to my panel (this is the first block of my code above).

 pnlScripts.add(lstScripts, BorderLayout.WEST);

And as my code above showed, the listScripts JList had a custom transferhandler set as such:

 this.lstScripts.setTransferHandler(lh);

So the transferhandler does all the user dnd (drag and drop) stuff. In the controller, I can get the updated list by doing:

 DefaultListModel model = (DefaultListModel)lstScripts.getModel();
 for (int i = 0; i < model.getSize(); i++){
     scriptnames += model.getElementAt(i).toString() + ",";
 }

The scriptnames String variable now contains the updated list.

Thanks!

Java Swing - Dynamically change JList using TransferHandler

1 Answers1