Blog @ SIB Visions » DnD https://blog.sibvisions.com Blog @ SIB Visions Mon, 30 Mar 2026 11:14:36 +0000 en hourly 1 Simple Drop File Support for JVx applications https://blog.sibvisions.com/2017/03/28/simple-drop-file-support-for-jvx-applications/ https://blog.sibvisions.com/2017/03/28/simple-drop-file-support-for-jvx-applications/#comments Tue, 28 Mar 2017 10:16:42 +0000 rjahn https://blog.sibvisions.com/?p=6461 Our next update release of VisionX will support Dropping files. It's a very useful feature and was easy to implement. Sure, it's a Swing specific feature, but our VisionX is more or less JVx Swing UI based.

Get a first impression

VisionX Drop file support

We drop an exported application archive into VisionX and the import wizard is starting. It's also possible to Drop a file directly into the import wizard.

VisionX is a JVx application and it's super easy to implement such feature for your own JVx application. Here's a code snippet how it'll work:

public SimpleFileDropHandler addTarget(IComponent pTarget, IFileHandleReceiver pListener,
                                       String... pExtension)
{
    Object oResource = pTarget.getResource();
   
    if (!(oResource instanceof JComponent) && !(oResource instanceof JFrame))
    {
        throw new IllegalArgumentException("Given object can't be a drop target!");
    }
   
    SimpleFileDropHandler handler = new SimpleFileDropHandler(pListener, pExtension);
   
    if (oResource instanceof JFrame)
    {
        ((JFrame)oResource).setTransferHandler(handler);
    }
    else
    {
        JComponent jcomp = getComponent((JComponent)oResource);
       
        if (jcomp != null)
        {
            jcomp.setTransferHandler(handler);
        }
    }
}

private JComponent getComponent(JComponent pComponent)
{
    if (pComponent instanceof JVxEditor)
    {
        JComponent comp = ((JVxEditor)pComponent).
                          getCellEditorHandler().getCellEditorComponent();
       
        if (comp instanceof JScrollPane)
        {
            Component cView = ((JScrollPane)comp).getViewport().getView();
           
            if (cView instanceof JComponent)
            {
                return ((JComponent)cView);                    
            }
            else
            {
                return null;
            }
        }
        else
        {
            return comp;
        }
    }
    else
    {
        return pComponent;
    }        
}

In principle, we set the TransferHandler for a JComponent. Above code detects the right JComponent because there's a difference if you use an IEditor.

The TransferHandler could be implemented like our SimpleFileDropHandler

public class SimpleFileDropHandler extends TransferHandler
{
    private IFileHandleReceiver listener;
   
    private String[] extensions;
       
    public SimpleFileDropHandler(IFileHandleReceiver pListener, String... pExtension)
    {
        listener = pListener;
        extensions = pExtension;
    }
   
    @Override
    public boolean canImport(TransferHandler.TransferSupport pSupport)
    {
        if (!pSupport.isDrop())
        {
            return false;
        }

        if (!pSupport.isDataFlavorSupported(DataFlavor.javaFileListFlavor))
        {
            return false;
        }

        boolean copySupported = (COPY & pSupport.getSourceDropActions()) == COPY;
       
        if (copySupported)
        {
            pSupport.setDropAction(TransferHandler.COPY);
            return true;
        }            
       
        return false;
    }
   
    @Override
    public boolean importData(TransferHandler.TransferSupport support)
    {
        if (!support.isDrop())
        {
            return false;
        }

        List<File> files;
        try
        {
            files = (List<File>)support.getTransferable().
                    getTransferData(DataFlavor.javaFileListFlavor);
        }
        catch (UnsupportedFlavorException ex)
        {
            // should never happen (or JDK is buggy)
            return false;
        }
        catch (IOException ex)
        {
            // should never happen (or JDK is buggy)
            return false;
        }
       
        if (listener != null)
        {
            for (File file : files)
            {
                try
                {
                    listener.receiveFileHandle(new FileHandle(file));
                }
                catch (Exception e)
                {
                    ExceptionHandler.raise(e);
                }
            }
        }
       
        return true;
    }
}

Have fun ;-)

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