Classes which implement this interface provide methods
that deal with the expanding and collapsing of <code>ExpandItem</code>s.
<p>
After creating an instance of a class that :
this interface it can be added to a <code>ExpandBar</code>
control using the <code>addExpandListener</code> method and
removed using the <code>removeExpandListener</code> method.
When a item of the <code>ExpandBar</code> is expanded or
collapsed, the appropriate method will be invoked.
</p>
Classes which implement this interface provide methods that deal with the expanding and collapsing of <code>ExpandItem</code>s.
<p> After creating an instance of a class that : this interface it can be added to a <code>ExpandBar</code> control using the <code>addExpandListener</code> method and removed using the <code>removeExpandListener</code> method. When a item of the <code>ExpandBar</code> is expanded or collapsed, the appropriate method will be invoked. </p>
@see ExpandAdapter @see ExpandEvent
@since 3.2