public class DNDSelectionFix implements SelectionListener, MouseListener {

	private boolean mouseDown;
	private boolean mouseUp;
	private boolean selected;
	private Tree tree;

	@Override
	public void widgetDefaultSelected(SelectionEvent e) {
		// TODO Auto-generated method stub

	}

	@Override
	public void widgetSelected(SelectionEvent e) {
		if (!mouseDown) {
			yourMethod();
		}
		else{
			selected = true;	
		}
		mouseDown = false;
		mouseUp = false;
	}

	private void yourMethod() {
		//if tree
		TreeItem[] selection = tree.getSelection();
		//if TreeViewer then get the selection from the treeviewer
	}

	@Override
	public void mouseDoubleClick(MouseEvent e) {
		// TODO Auto-generated method stub

	}

	@Override
	public void mouseDown(MouseEvent e) {
		mouseDown = true;
		mouseUp = false;
	}

	@Override
	public void mouseUp(MouseEvent e) {
		mouseUp = true;
		mouseDown = false;
		if(selected)
		{
			yourMethod();
			selected=false;
                        mouseUp = false;
		        mouseDown = false;
		}
	}
}