ctively, then the new widget replaces the old widget by
updating the underlying element (i.e., by calling <code>Element.update</code> with the
new widget). Otherwise, the old element is removed from the tree, the new
widget is inflated into an element, and the new element is inserted into the
tree.</p>
<p>In addition, using a <code>GlobalKey</code> as the widget's <a href="../../gs_form_widget_fields_radio_group_field/RadioItem/key.html">key</a> allows the element
to be moved around the tree (changing paren