MACROMEDIA FLASH 8-USING FLASH, Руководство пользователя, Страница: 531 / 678

Creating accessibility with ActionScript 531
When updating accessibility properties of multiple objects at once, you need to include only a
single call to
Accessiblity.updateProperties
(too frequent updates to the screen reader
can cause some screen readers to become too verbose).
See
updateProperties (Accessibility.updateProperties method)
in the ActionScript 2.0 Language
Reference.
Implementing screen reader detection with the
Accessibility.isActive() method
To create Flash content that behaves in a specific way if a screen reader is active, you can use
the ActionScript method
Accessibility.isActive()
, which returns a value of
true
if a
screen reader is present, and
false
otherwise. You can then design your Flash content to
perform so that it’s compatible with screen reader use (for example, by hiding child elements
from the screen reader). For more information, see isActive (Accessibility.isActive
method)
in ActionScript 2.0 Language Reference.
For example, you could use the
Accessibility.isActive()
method to decide whether to
include unsolicited animation. Unsolicited animation happens without the screen reader
doing anything, which can be confusing for screen readers.
The
Accessibility.isActive()
method provides asynchronous communication between
the Flash content and Flash Player, which means that a slight real-time delay can occur
between the time the method is called and the time in which Flash Player becomes active,
returning an incorrect value of
false
. To ensure that the method is called correctly, you can
do one of the following:
■
Instead of using the
Accessibility.isActive()
method when the Flash content first
plays, call the method whenever you need to make a decision about accessibility.
■
Introduce a short delay of one or two seconds at the beginning of your document to give
the Flash content enough time to contact Flash Player.
For example, you can attach this method with an
onFocus
event to a button. This
generally gives the SWF file enough time to load and you can safely assume a screen reader
user will tab to the first button or object on the Stage.