Tooltip on tree viewer items

This describes about how to add a tooltip on tree viewer items based on the context of object. 

ExplorerViewer.getTree().addMouseTrackListener(new ExplorerMouseListener());

private class ExplorerMouseListener implements MouseTrackListener {

@Override

public void mouseEnter(MouseEvent e) {

}

@Override

public void mouseExit(MouseEvent e) {

}

@Override

public void mouseHover(MouseEvent event) {

TreeItem item = explorerViewer.getTree().getItem(new Point(event.x, event.y));

if (item != null && item.getData() instanceof MyResource) {

MyResource selectedElement = (MyResource) item.getData();

if (selectedElement.getResourceType() == MyResourceType.APP_GROUP

|| selectedElement.getResourceType() == MyResourceType.DATA) {

if (selectedElement.getData() instanceof INameDescription)

explorerViewer.getTree().setToolTipText(

((INameDescription) selectedElement.getData())

.getDescription());

} else {

explorerViewer.getTree().setToolTipText(null);

}

}

}

}