| The common superclass of all high-level user interface classes. The
contents displayed and their interaction with the user are defined by
subclasses.
Using subclass-defined methods, the application may change the contents
of a Screen object while it is shown to the user. If
this occurs, and the
Screen object is visible, the display will be updated
automatically. That
is, the implementation will refresh the display in a timely fashion without
waiting for any further action by the application. For example, suppose a
List object is currently displayed, and every element
of the List is
visible. If the application inserts a new element at the beginning of the
List, it is displayed immediately, and the other
elements will be
rearranged appropriately. There is no need for the application to call
another method to refresh the display.
It is recommended that applications change the contents of a
Screen only
while it is not visible (that is, while another
Displayable is current).
Changing the contents of a Screen while it is visible
may result in
performance problems on some devices, and it may also be confusing if the
Screen's contents changes while the user is
interacting with it.
In MIDP the four Screen methods that defined
read/write ticker and
title properties were moved to Displayable,
Screen's superclass. The
semantics of these methods have not changed. |
