mx.accessibility.TreeAccImpl

Package	mx.accessibility
Class	public class TreeAccImpl
Inheritance	TreeAccImpl AccImpl AccessibilityImplementation

Review Needed

The TreeAccImpl class, also called the Tree Accessiblity Implementation class, is used to make a Tree component accessible.

The TreeAccImpl class supports system roles, object-based events, and states.

A Tree reports the role ROLE_SYSTEM_OUTLINE (0x23) to a screen reader. Items of a Tree report the role ROLE_SYSTEM_OUTLINEITEM (0x24).

A Tree reports the following states to a screen reader:

STATE_SYSTEM_NORMAL (0x00000000)
STATE_SYSTEM_UNAVAILABLE (0x00000001)
STATE_SYSTEM_FOCUSED (0x00000004)
STATE_SYSTEM_FOCUSABLE (0x00100000)

Additionally, items of a Tree report the following states:

STATE_SYSTEM_SELECTED (0x00000002)
STATE_SYSTEM_FOCUSED (0x00000004)
STATE_SYSTEM_INVISIBLE (0x00008000)
STATE_SYSTEM_OFFSCREEN (0x00010000)
STATE_SYSTEM_SELECTABLE (0x00200000)
STATE_SYSTEM_COLLAPSED (0x00000400)
STATE_SYSTEM_EXPANDED (0x00000200)

A Tree dispatches the following events to a screen reader:

EVENT_OBJECT_FOCUS (0x8005)
EVENT_OBJECT_SELECTION (0x8006)
EVENT_OBJECT_STATECHANGE (0x800A)
EVENT_OBJECT_NAMECHANGE (0x800C)

	Property	Defined by
		errno : uint Errors are indicated out-of-band, rather than in return values.	AccessibilityImplementation
		stub : Boolean If a component is released without an ActionScript accessibility implementation, it is strongly suggested that a component accessibility stub be included.	AccessibilityImplementation

	Property	Defined by
		eventsToHandle : Array [read-only] All AccImpl subclasses must override this function by returning an array of strings of the events for which the class should listen from its master component.	TreeAccImpl
		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

	Method	Defined by
		TreeAccImpl(master:UIComponent) Creates a new TreeAccImpl instance for the specified Tree component.	TreeAccImpl
		accDoDefaultAction(childID:uint):void IAccessible method for performing the default action associated with a treeItem, which is Expand or Collapse depending on the item state.	TreeAccImpl
		accLocation(childID:uint):* IAccessible method for returning the bounding box of a treeItem.	TreeAccImpl
		accSelect(selFlag:uint, childID:uint):void IAccessible method for altering the selection in the component that this AccessibilityImplementation represents.	AccessibilityImplementation
		enableAccessibility():void [static] Method call for enabling accessibility for a component.	TreeAccImpl
		get_accDefaultAction(childID:uint):String IAccessible method for returning the default action.	TreeAccImpl
		get_accFocus():uint IAccessible method for returning the childFocus of the ListBase.	TreeAccImpl
		get_accName(childID:uint):String IAccessible method for returning the name for the component that this AccessibilityImplementation represents or for one of its child elements.	AccImpl
		get_accRole(childID:uint):uint IAccessible method for returning system role for the component.	TreeAccImpl
		get_accSelection():Array IAccessible method for returning an array containing the IDs of all child elements that are selected.	AccessibilityImplementation
		get_accState(childID:uint):uint IAccessible method for returning the state of the TreeItem.	TreeAccImpl
		get_accValue(childID:uint):String IAccessible method for returning the value of the TreeItem/Tree which is spoken out by the screen reader.	TreeAccImpl
		getChildIDArray():Array Method to return an array of childIDs.	TreeAccImpl

	Method	Defined by
		eventHandler(event:Event):void Override the generic event handler.	TreeAccImpl
		getName(childID:uint):String Method for returning the name of the TreeItem/Tree which is spoken out by the screen reader.	TreeAccImpl
		getState(childID:uint):uint Returns the state of the accessible component.	AccImpl

Property detail

eventsToHandle

property

eventsToHandle:Array [read-only]

All AccImpl subclasses must override this function by returning an array of strings of the events for which the class should listen from its master component.

Implementation
protected function get eventsToHandle():Array

Constructor detail

TreeAccImpl

()

constructor

public function TreeAccImpl(master:UIComponent)

Creates a new TreeAccImpl instance for the specified Tree component.

Direct calls to the AccImpl subclass constructors are unneccessary. When a Flex project is compiled with Generate accessible SWF file set to true, the compiler instantiates the accessibility implementations for the components used in the project that have them by calling the the static enableAccessibility() method.

Parameters

master:UIComponent — The UIComponent instance that this TreeAccImpl instance is making accessible.

Method detail

accDoDefaultAction

()

method

public override function accDoDefaultAction(childID:uint):void

IAccessible method for performing the default action associated with a treeItem, which is Expand or Collapse depending on the item state.

Parameters

childID:uint — An unsigned integer corresponding to one of the component's child elements as defined by getChildIDArray().

accLocation

()

method

public override function accLocation(childID:uint):*

IAccessible method for returning the bounding box of a treeItem.

Parameters

childID:uint — An unsigned integer corresponding to one of the component's child elements as defined by getChildIDArray().

Returns

* — Location Object

enableAccessibility

()

method

public static function enableAccessibility():void

Method call for enabling accessibility for a component. This method is required for the compiler to activate the accessibility classes for a component.

When a Flex project is compiled with the Generate accessible SWF file set to true, the Flex compiler automatically enables accessibility implementations for the components used in the project that have them.

Accessible component classes should include the [AccessibilityClass] meta tag to specify the appropriate AccImpl subclass or accessibility implementation and let the compiler know to call enableAccessibility().

Example
Following is an example showing how the [AccessibilityClass] meta tag specifies the appropriate AccImpl subclass or accessibility implementation for the mx.controls.Tree component.

[AccessibilityClass(implementation="mx.accessibility.TreeAccImpl")]

eventHandler

()

method

protected override function eventHandler(event:Event):void

Override the generic event handler. Each AccImpl subclass must implement this method to listen for events from its master component.

Parameters

event:Event — The event object.

get_accDefaultAction

()

method

public override function get_accDefaultAction(childID:uint):String

IAccessible method for returning the default action. For child treeItems, the default action is Expand or Collapse depending on the item state, but for the Tree component itself, null is returned.

Parameters

childID:uint — An unsigned integer corresponding to one of the component's child elements as defined by getChildIDArray().

Returns

String — DefaultAction String

get_accFocus

()

method

public override function get_accFocus():uint

IAccessible method for returning the childFocus of the ListBase.

Returns

uint — focused childID.

get_accRole

()

method

public override function get_accRole(childID:uint):uint

IAccessible method for returning system role for the component. System roles are predefined for all the components in MSAA.

A Tree component, ( childID == 0 ), reports the role ROLE_SYSTEM_OUTLINE (0x23). Items of a ListBase component ( childID >= 1 ) report the role ROLE_SYSTEM_OUTLINEITEM (0x24).

Parameters

childID:uint — An unsigned integer corresponding to one of the component's child elements as defined by getChildIDArray().

Returns

uint — Role associated with the component.

get_accState

()

method

public override function get_accState(childID:uint):uint

IAccessible method for returning the state of the TreeItem. States are predefined for all the components in MSAA. Values are assigned to each state. Depending upon the treeItem being Selected, Selectable, Invisible, Offscreen, Expanded or Collapsed a value is returned.

Parameters

childID:uint — An unsigned integer corresponding to one of the component's child elements as defined by getChildIDArray().

Returns

uint — State depending upon the treeItem being Selected, Selectable, Invisible, Offscreen, Expanded or Collapsed

get_accValue

()

method

public override function get_accValue(childID:uint):String

IAccessible method for returning the value of the TreeItem/Tree which is spoken out by the screen reader. The Tree should return the name of the currently selected item with an "m of n" string as its value.

Parameters

childID:uint — uint

Returns

String — Value String

getChildIDArray

()

method

public override function getChildIDArray():Array

Method to return an array of childIDs.

Returns

Array — An array of unsigned integer IDs, one for each treeItem defined in the Tree component's dataProvider.

getName

()

method

protected override function getName(childID:uint):String

Method for returning the name of the TreeItem/Tree which is spoken out by the screen reader. The TreeItem should return the label as the name with an "m of n" string and Tree should return the name specified by the AccessibilityProperties.name.

Parameters

childID:uint — uint

Returns

String — Name String

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