Packagemx.accessibility
Classpublic class AccImpl
InheritanceAccImpl Inheritance flash.accessibility.AccessibilityImplementation
Subclasses AccordionHeaderAccImpl, ButtonAccImpl, ButtonBaseAccImpl, ComboBaseAccImpl, DateChooserAccImpl, DateFieldAccImpl, LabelAccImpl, ListBaseAccImpl, ListBaseAccImpl, MenuBarAccImpl, PanelAccImpl, PanelAccImpl, RichEditableTextAccImpl, SliderAccImpl, SliderBaseAccImpl, SpinnerAccImpl, TabBarAccImpl, TextBaseAccImpl, TreeAccImpl, VideoPlayerAccImpl

Language Version : ActionScript 3.0
Product Version : Flex 3
Runtime Versions : Flash Player 9, AIR 1.1

AccImpl is Flex's base accessibility implementation class for MX and Spark components.

It is a subclass of the Flash Player's AccessibilityImplementation class.

When an MX or Spark component is created, its accessibilityImplementation property is set to an instance of a subclass of this class. The Flash Player then uses this object to allow MSAA clients such as screen readers to see and manipulate the component. See the flash.accessibility.AccessibilityImplementation class for additional information about accessibility implementation classes and MSAA.

Children

The Flash Player does not support a true hierarchy of accessible objects. If a DisplayObject has an accessibilityImplementation object, then the accessibilityImplementation objects of its children are ignored. However, the Player does allow a component's accessibility implementation class to expose MSAA information for its internal parts. (For example, a List exposes MSAA information about its items.)

The number of children (internal parts) and the child IDs used to identify them are determined by the getChildIDArray() method. In the Player's AccessibilityImplementation base class, this method simply returns null. Flex's AccImpl class overrides it to return an empty array. It also provides a protected utility method, createChildIDArray() which subclasses with internal parts can use in their overrides.

Role

The MSAA Role of a component and its internal parts is determined by the get_accRole() method. In the Player's AccessibilityImplementation base class, this method throws a runtime error, since subclasses are expected to override it. Flex's AccImpl class has a protected role property which subclasses generally set in their constructor, and it overrides get_accRole() to return this property.

Name

The MSAA Name of a component and its internal parts is determined by the get_accName() method. In the Player's AccessibilityImplementation base class, this method simply returns null. Flex's AccImpl class overrides it to construct a name as follows, starting with an empty string and separating added portions with a single space:

Description

The MSAA Description is determined solely by a component's accessibilityProperties object and not by its accessibilityImplementation object. Therefore there is no logic in AccessibilityImplementation or AccImpl or any subclasses of AccImpl related to the description. The normal way to set the description in Flex is via the accessibilityDescription property on UIComponent, which simply sets accessibilityProperties.description.

State

The MSAA State of a component and its internal parts is determined by the get_accState() method. In the Player's AccessibilityImplementation base class, this method throws a runtime error, since subclasses are expected to override it. Flex's AccImpl class does not override it, but provides a protected utility method, getState(), for subclasses to use in their overrides. The getState() method determines the state as a combination of

Note that by default all components are assumed to be focusable and thus the accessibility implementation classes for non-focusable components like Label must clear this state flag. When a component has a state of unavailable, the focusable state is removed by the accessibility implementation class.

Value

The MSAA Value of a component and its internal parts is determined by the get_accValue() method. In the Player's AccessibilityImplementation base class, this method simply returns null. Flex's AccImpl class does not override it, but subclasses for components like TextInput do.

Location

The MSAA Location for a component's internal parts, but not the component itself, is determined by the get_accLocation() method. This method is never called with a childID of 0; instead, the Flash Player determines the MSAA Location of a component based on its bounding rectangle as determined by getBounds(). Flex's AccImpl class does not override this method, but subclasses for components with internal parts do.

Default Action

The MSAA DefaultAction for a component and its internal parts is determined by the get_accDefaultAction() method. In the Player's AccessibilityImplementation base class, this method simply returns null. Flex's AccImpl class does not override it, but subclasses with default actions do. These subclasses also override AccessibilityImplementation's accDoDefaultAction() method to perform the default action that they advertise.

Other

The MSAA events EVENT_OBJECT_SHOW and EVENT_OBJECT_HIDE are sent when the object is shown or hidden. The corresponding states for these are covered by the Flash Player which does not render any MSAA components that are hidden. When the component is shown the states mentioned for AccImpl are used.



Protected Properties
 PropertyDefined By
  eventsToHandle : Array
[read-only] All subclasses must override this function by returning an array of strings of the events to listen for.
AccImpl
  master : UIComponent
A reference to the UIComponent instance that this AccImpl instance is making accessible.
AccImpl
  role : uint
Accessibility role of the component being made accessible.
AccImpl
Public Methods
 MethodDefined By
  
Constructor.
AccImpl
  
getFormName(component:UIComponent):String
[static] Method for supporting Form Accessibility.
AccImpl
  
isAncestorDisabled(component:UIComponent):Boolean
[static] Returns true if an ancestor of the component has enabled set to false.
AccImpl
Protected Methods
 MethodDefined By
  
eventHandler(event:Event):void
Generic event handler.
AccImpl
  
getName(childID:uint):String
Returns the name of the accessible component.
AccImpl
  
getState(childID:uint):uint
Utility method to determine state of the accessible component.
AccImpl
Property Detail
eventsToHandleproperty
eventsToHandle:Array  [read-only]

Language Version : ActionScript 3.0
Product Version : Flex 3
Runtime Versions : Flash Player 9, AIR 1.1

All subclasses must override this function by returning an array of strings of the events to listen for.


Implementation
    protected function get eventsToHandle():Array
masterproperty 
protected var master:UIComponent

Language Version : ActionScript 3.0
Product Version : Flex 3
Runtime Versions : Flash Player 9, AIR 1.1

A reference to the UIComponent instance that this AccImpl instance is making accessible.

roleproperty 
protected var role:uint

Language Version : ActionScript 3.0
Product Version : Flex 3
Runtime Versions : Flash Player 9, AIR 1.1

Accessibility role of the component being made accessible.

Constructor Detail
AccImpl()Constructor
public function AccImpl(master:UIComponent)

Language Version : ActionScript 3.0
Product Version : Flex 3
Runtime Versions : Flash Player 9, AIR 1.1

Constructor.

Parameters
master:UIComponent — The UIComponent instance that this AccImpl instance is making accessible.
Method Detail
eventHandler()method
protected function eventHandler(event:Event):void

Language Version : ActionScript 3.0
Product Version : Flex 3
Runtime Versions : Flash Player 9, AIR 1.1

Generic event handler. All AccImpl subclasses must implement this to listen for events from its master component.

Parameters

event:Event

getFormName()method 
public static function getFormName(component:UIComponent):String

Language Version : ActionScript 3.0
Product Version : Flex 3
Runtime Versions : Flash Player 9, AIR 1.1

Method for supporting Form Accessibility. Called from get_accName() in this AccImpl class. Also called from the UIComponentAccProps constructor.

Parameters

component:UIComponent

Returns
String
getName()method 
protected function getName(childID:uint):String

Language Version : ActionScript 3.0
Product Version : Flex 3
Runtime Versions : Flash Player 9, AIR 1.1

Returns the name of the accessible component. All subclasses must implement this instead of implementing get_accName().

Parameters

childID:uint

Returns
String
getState()method 
protected function getState(childID:uint):uint

Language Version : ActionScript 3.0
Product Version : Flex 3
Runtime Versions : Flash Player 9, AIR 1.1

Utility method to determine state of the accessible component.

Parameters

childID:uint

Returns
uint
isAncestorDisabled()method 
public static function isAncestorDisabled(component:UIComponent):Boolean

Returns true if an ancestor of the component has enabled set to false. The given component itself is not checked.

Parameters

component:UIComponent — The UIComponent to check for a disabled ancestor.

Returns
Boolean — true if the component has a disabled ancestor.