public void addPropertyProvider(String groupLabel, final PropertyProvider<?> propertyProvider) {
if (propertyProvider.getProperties().size() > 0) {
final UIButton expand = new UIButton("", "-");
expand.setTooltip("Click to collapse");
final UILabel headline = new UILabel(groupLabel);
final MigLayout layout = new MigLayout();
layout.setColConstraints("[min][fill]");
layout.setRowConstraints("[min]");
expand.subscribe(new ActivateEventListener() {
@Override
public void onActivated(UIWidget widget) {
UIButton button = (UIButton) widget;
if ("-".equals(button.getText())) {
layout.clear();
invalidate();
button.setText("+");
button.setTooltip("Click to expand");
} else {
expand(propertyProvider, layout);