Asynchronous drag to file explorer

Question

Hello,
I made a file upload/download application (ssh/sftp + metadata). My application shows a tree + a list of remote files. I'd like to be able to drag one from the list to a windows explorer.
Alas, I can't see a way to solve this: how can I initiate a transfer in the background and drop the downloaded file to the target folder, without blocking the gui?
Did a lot of search for this, but I guess this is a guru topic. Or is it infeasible?

Answer 1

Well, I was hoping to be able to just use override TransferHandler. I didn't try further, because the overriden method has to return something ; creating a thread wouldn't return a result directly, so I know this isn't my solution.
You said explorer should download the file... But how can I give a File object back to Explorer, if I didn't download it myself yet ?
Here is my TransferHandler:
private class FileTransferHandler extends TransferHandler {
@Override
protected Transferable createTransferable(JComponent c) {
final File targetDirFile;
try {
targetDirFile = File.createTempFile("happypf", "tempdir");
} catch (IOException exception) {
throw new RuntimeException(exception);
targetDirFile.delete();
targetDirFile.mkdir();
final List<RemoteFile> remoteFiles = getSelectedRemoteFiles();
// this is my problem... I need to do something with those remoteFiles...
Transferable transferable = new Transferable() {
public DataFlavor[] getTransferDataFlavors() {
DataFlavor[] flavors = { DataFlavor.javaFileListFlavor };
return flavors;
public boolean isDataFlavorSupported(DataFlavor flavor) {
return flavor.equals(DataFlavor.javaFileListFlavor);
public List<File> getTransferData(DataFlavor flavor) throws UnsupportedFlavorException, IOException {
if (!isDataFlavorSupported(flavor)) {                       
throw new UnsupportedFlavorException(flavor);
return new ArrayList<File>();
return transferable;
//[... removed canImport / importDate for explorer->java, which work...]
}