E4: drag an object from a TableViewer to Windows Explorer (or OS specific file system) - eclipse

Question

In my Eclipse RCP application I display some business data in a TableViewer.
I want the user to be able to drag a row from the table viewer and drop it on the windows desktop/explorer. Windows should then create a file with the data from the selected row that I could provide in the dragSetData(..) method of the DragSourceAdapter class.
How to implement this? It seems that using FileTransfer as the dragSourceSupport on the table viewer is the way to go as it trigger a call to the dragSetData() method. But what object should I create and assign to "event.data" in this method?
A working example would be appreciated.
I've implemented the reverse without problem, i.e. drag a file from windows explorer onto the TableViewer and add a row in the table. There are plenty on sample for this on the net but can't find a sample of the opposite, drag from eclipse to the OS
[edit + new requirement]
So I understand that I have to create a temporary file somewhere and set the name of that temp file in event.data in dragSetData()
Q: is there a simpler way to do that, eg set somewhere (iun data) the content of the file directly without the temp file?
There is another requirement. When the drop operation is about to occur, I want to show a popup to the user that will have to choose what "business data" from the "row" he wants to export and the name of the file that will be created. I tried the following (only asking for the filename for now) but it does not work as expected as the popup shows up as soon as the cursor reach the first pixel outside my app. I would like to show the popup just "before" the drop operation occurs.
Q: is there a way to have this popup show just before the drop operation occurs, ie when the user "release" the mouse button?
#Override
public void dragSetData(final DragSourceEvent event){
if (FileTransfer.getInstance().isSupportedType(event.dataType)) {
// Will be a more complex dialog with multiple fields..
InputDialog inputDialog = new InputDialog(shell, "Please enter a file name", "File Name:", "", null);
if (inputDialog.open() != Window.OK) {
event.doit = false;
return;
}
event.data = new String[] { inputDialog.getValue() };
}
}

Answer 1

The event.data for FileTransfer is an array of file path strings.
You DragSourceAdapter class might look something like:
public class MyDragSourceAdapter extends DragSourceAdapter
{
private final StructuredViewer viewer;
public MyDragSourceAdapter(final StructuredViewer viewer)
{
super();
this.viewer = viewer;
}
#Override
public void dragStart(final DragSourceEvent event)
{
IStructuredSelection selection = viewer.getStructuredSelection();
if (selection == null)
return;
// TODO check if the selection contains any files
// TODO set event.doit = false if not
}
#Override
public void dragSetData(final DragSourceEvent event)
{
if (!FileTransfer.getInstance().isSupportedType(event.dataType))
return;
IStructuredSelection selection = viewer.getStructuredSelection();
List<String> files = new ArrayList<>(selection.size());
// TODO add files in the selection to 'files'
event.data = files.toArray(new String [files.size()]);
}
}
and you install it on your viewer with:
MyDragSourceAdapter adapter = new MyDragSourceAdapter(viewer);
viewer.addDragSupport(DND.DROP_COPY, new Transfer [] {FileTransfer.getInstance()}, adapter);