public class FolderDragListener extends DragSourceAdapter {

	private StructuredViewer viewer;

	public FolderDragListener(StructuredViewer viewer) {
		this.viewer = viewer;
	}

	@Override
	public void dragFinished(DragSourceEvent event) {
		System.out.println("__________________dragFinished()__________________");		
		if (!event.doit)
			return;
		viewer.refresh();
	}

	@Override
	public void dragSetData(DragSourceEvent event) {
		System.out.println("__________________dragSetData()__________________");
		
		IStructuredSelection selection = (IStructuredSelection)viewer.getSelection();
		Folder folder = (Folder)selection.getFirstElement();	   
	    if (PluginTransfer.getInstance().isSupportedType(event.dataType)) {
	        event.data = folder;
	    }
	}

	@Override
	public void dragStart(DragSourceEvent event) {
		System.out.println("__________________dragStart()__________________");		
		IStructuredSelection selection = (IStructuredSelection)viewer.getSelection();
	    Folder folder = (Folder)selection.getFirstElement();				
		event.doit = true ;
	}
}

public class FolderTreeDropAdapter extends ViewerDropAdapter {

	public FolderTreeDropAdapter(TreeViewer viewer) {
		super(viewer);		
	}

	@Override
	public boolean performDrop(Object data) {
		System.out.println("___________Perform_drop()__________________");
		Folder target = (Folder)getCurrentTarget();
	      if (target == null)
	         target = (Folder)getViewer().getInput();
	      Folder toDrop = (Folder)data;
	      TreeViewer viewer = (TreeViewer)getViewer();
	      //cannot drop a folder onto itself or a child
	      if (toDrop.equals(target) || isParentOf(toDrop, target))
	            return false;	    
	         toDrop.setParent(target);
	         viewer.refresh();
	      return true;
	}

	@Override
	public boolean validateDrop(Object target, int operation,
			TransferData transferType) {
		
		boolean valid = PluginTransfer.getInstance().isSupportedType(transferType);
		System.out.println("__________________validateDrop()__________________");
		System.out.println("Target:" +((Folder)target).getName()+ "  validate: "+ valid);
		return valid ;
	}
	
	private boolean isParentOf(Folder source, Folder target)
	{
		 Folder folder = target;
	      while (folder.getParent() != null)
	      {
	    	  if (folder.getParent() == source )
	    		  return true;
	    	  folder = folder.getParent();
	      }
		return false;
	}
}

public class FolderTreeView extends ViewPart {
	
	public static final String ID = "de.rcp.folderTreeView";
	
	private TreeViewer viewer;	
	private FolderTreeDropAdapter dropAdapter;
	
	public FolderTreeView() {		
	}

	@Override
	public void createPartControl(Composite parent) {
		
		viewer = new TreeViewer(parent, SWT.SINGLE | SWT.H_SCROLL
				| SWT.V_SCROLL | SWT.FULL_SELECTION | SWT.BORDER);
		viewer.setContentProvider(new FolderTreeContentProvider());
		viewer.setLabelProvider(new FolderTreeLabelProvider());
		viewer.setInput(PersonModelProvider.getInstance().getPersons());
		addDndSupport(viewer);
	}
	
	private void addDndSupport(TreeViewer viewer)
	{
		int ops = DND.DROP_MOVE;
	    Transfer[] transfers = new Transfer[] { PluginTransfer.getInstance()};
	    viewer.addDragSupport(ops, transfers, new FolderDragListener(viewer));
	    transfers = new Transfer[] {PluginTransfer.getInstance()};
	    dropAdapter = new FolderTreeDropAdapter(viewer);
	    viewer.addDropSupport(ops, transfers, dropAdapter);
	}

	@Override
	public void setFocus() {
		viewer.getTree().setFocus();
	}
}