In the example below, listeners for a single event MouseEvent.MOUSE_DOWN,
are created on two flex check boxes controls, due to which whenever the check boxes are clicked the
second argument of the .addEventListener method is get switched.
Here the second
argument of .addEventListener method is a function name eventHandler
that contains show method of Alert class.
This show method when invoked opens the pop-up windows. So with this example a clear idea for adding single event listeners in to
several components is depicted.