Added in API level 14

Summary: Ctors | Methods | Inherited Methods

View.AccessibilityDelegate

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Kotlin |Java

public static class View.AccessibilityDelegate
extends Object

java.lang.Object
↳	android.view.View.AccessibilityDelegate

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This class represents a delegate that can be registered in a View to enhance accessibility support via composition rather via inheritance. It is specifically targeted to widget developers that extend basic View classes i.e. classes in package android.view, that would like their applications to be backwards compatible.

Developer Guides

For more information about making applications accessible, read the Accessibility developer guide.

A scenario in which a developer would like to use an accessibility delegate is overriding a method introduced in a later API version than the minimal API version supported by the application. For example, the method View#onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo) is not available in API version 4 when the accessibility APIs were first introduced. If a developer would like their application to run on API version 4 devices (assuming all other APIs used by the application are version 4 or lower) and take advantage of this method, instead of overriding the method which would break the application's backwards compatibility, they can override the corresponding method in this delegate and register the delegate in the target View if the API version of the system is high enough, i.e. the API version is the same as or higher than the API version that introduced View#onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo).

Here is an example implementation:

 if (Build.VERSION.SDK_INT >= 14) {
     // If the API version is equal of higher than the version in
     // which onInitializeAccessibilityNodeInfo was introduced we
     // register a delegate with a customized implementation.
     View view = findViewById(R.id.view_id);
     view.setAccessibilityDelegate(new AccessibilityDelegate() {
         public void onInitializeAccessibilityNodeInfo(View host,
                 AccessibilityNodeInfo info) {
             // Let the default implementation populate the info.
             super.onInitializeAccessibilityNodeInfo(host, info);
             // Set some other information.
             info.setEnabled(host.isEnabled());
         }
     });
 }
 

This delegate contains methods that correspond to the accessibility methods in View. If a delegate has been specified the implementation in View hands off handling to the corresponding method in this delegate. The default implementation the delegate methods behaves exactly as the corresponding method in View for the case of no accessibility delegate been set. Hence, to customize the behavior of a View method, clients can override only the corresponding delegate method without altering the behavior of the rest accessibility related methods of the host view.

Note: On platform versions prior to API 23, delegate methods on views in the android.widget.* package are called before host methods. This prevents certain properties such as class name from being modified by overriding AccessibilityDelegate#onInitializeAccessibilityNodeInfo(View, AccessibilityNodeInfo), as any changes will be overwritten by the host class.

Starting in API 23, delegate methods are called after host methods, which all properties to be modified without being overwritten by the host class.

Note: Use a AccessibilityDelegateCompat wrapper instead of this class for backwards-compatibility.

Summary

Public constructors
AccessibilityDelegate()

Public methods
void	addExtraDataToAccessibilityNodeInfo(View host, AccessibilityNodeInfo info, String extraDataKey, Bundle arguments) Adds extra data to an AccessibilityNodeInfo based on an explicit request for the additional data.
boolean	dispatchPopulateAccessibilityEvent(View host, AccessibilityEvent event) Dispatches an AccessibilityEvent to the host View first and then to its children for adding their text content to the event.
AccessibilityNodeProvider	getAccessibilityNodeProvider(View host) Gets the provider for managing a virtual view hierarchy rooted at this View and reported to AccessibilityServices that explore the window content.
void	onInitializeAccessibilityEvent(View host, AccessibilityEvent event) Initializes an AccessibilityEvent with information about the the host View which is the event source.
void	onInitializeAccessibilityNodeInfo(View host, AccessibilityNodeInfo info) Initializes an AccessibilityNodeInfo with information about the host view.
void	onPopulateAccessibilityEvent(View host, AccessibilityEvent event) Gives a chance to the host View to populate the accessibility event with its text content.
boolean	onRequestSendAccessibilityEvent(ViewGroup host, View child, AccessibilityEvent event) Called when a child of the host View has requested sending an AccessibilityEvent and gives an opportunity to the parent (the host) to augment the event.
boolean	performAccessibilityAction(View host, int action, Bundle args) Performs the specified accessibility action on the view.
void	sendAccessibilityEvent(View host, int eventType) Sends an accessibility event of the given type.
void	sendAccessibilityEventUnchecked(View host, AccessibilityEvent event) Sends an accessibility event.

Inherited methods

From class java.lang.Object Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. final Class<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait(long timeoutMillis, int nanos) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait(long timeoutMillis) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait() Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Public constructors

AccessibilityDelegate

public AccessibilityDelegate ()

Public methods

addExtraDataToAccessibilityNodeInfo

public void addExtraDataToAccessibilityNodeInfo (View host, 
                AccessibilityNodeInfo info, 
                String extraDataKey, 
                Bundle arguments)

Adds extra data to an AccessibilityNodeInfo based on an explicit request for the additional data.

This method only needs to be implemented if the View offers to provide additional data.

The default implementation behaves as View#addExtraDataToAccessibilityNodeInfo(AccessibilityNodeInfo, String, Bundle)

Parameters
host	View
info	AccessibilityNodeInfo
extraDataKey	String
arguments	Bundle

dispatchPopulateAccessibilityEvent

Added in API level 14

public boolean dispatchPopulateAccessibilityEvent (View host, 
                AccessibilityEvent event)

Dispatches an AccessibilityEvent to the host View first and then to its children for adding their text content to the event.

The default implementation behaves as View#dispatchPopulateAccessibilityEvent(AccessibilityEvent) for the case of no accessibility delegate been set.

Parameters
host	View: The View hosting the delegate. This value cannot be null.
event	AccessibilityEvent: The event. This value cannot be null.

Returns
boolean	True if the event population was completed.

See also:

• View#dispatchPopulateAccessibilityEvent(AccessibilityEvent)

getAccessibilityNodeProvider

Added in API level 16

public AccessibilityNodeProvider getAccessibilityNodeProvider (View host)

Gets the provider for managing a virtual view hierarchy rooted at this View and reported to AccessibilityServices that explore the window content.

The default implementation behaves as View#getAccessibilityNodeProvider() for the case of no accessibility delegate been set.

Parameters
host	View: This value cannot be null.

Returns
AccessibilityNodeProvider	The provider. This value may be null.

See also:

• AccessibilityNodeProvider

onInitializeAccessibilityEvent

Added in API level 14

public void onInitializeAccessibilityEvent (View host, 
                AccessibilityEvent event)

Initializes an AccessibilityEvent with information about the the host View which is the event source.

The default implementation behaves as View#onInitializeAccessibilityEvent(AccessibilityEvent) for the case of no accessibility delegate been set.

Parameters
host	View: The View hosting the delegate. This value cannot be null.
event	AccessibilityEvent: The event to initialize. This value cannot be null.

See also:

• View#onInitializeAccessibilityEvent(AccessibilityEvent)

onInitializeAccessibilityNodeInfo

Added in API level 14

public void onInitializeAccessibilityNodeInfo (View host, 
                AccessibilityNodeInfo info)

Initializes an AccessibilityNodeInfo with information about the host view.

The default implementation behaves as View#onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo) for the case of no accessibility delegate been set.

Parameters
host	View: The View hosting the delegate. This value cannot be null.
info	AccessibilityNodeInfo: The instance to initialize. This value cannot be null.

See also:

• View#onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo)

onPopulateAccessibilityEvent

Added in API level 14

public void onPopulateAccessibilityEvent (View host, 
                AccessibilityEvent event)

Gives a chance to the host View to populate the accessibility event with its text content.

The default implementation behaves as View#onPopulateAccessibilityEvent(AccessibilityEvent) for the case of no accessibility delegate been set.

Parameters
host	View: The View hosting the delegate. This value cannot be null.
event	AccessibilityEvent: The accessibility event which to populate. This value cannot be null.

See also:

• View#onPopulateAccessibilityEvent(AccessibilityEvent)

onRequestSendAccessibilityEvent

Added in API level 14

public boolean onRequestSendAccessibilityEvent (ViewGroup host, 
                View child, 
                AccessibilityEvent event)

Called when a child of the host View has requested sending an AccessibilityEvent and gives an opportunity to the parent (the host) to augment the event.

The default implementation behaves as ViewGroup#onRequestSendAccessibilityEvent(View, AccessibilityEvent) for the case of no accessibility delegate been set.

Parameters
host	ViewGroup: The View hosting the delegate. This value cannot be null.
child	View: The child which requests sending the event. This value cannot be null.
event	AccessibilityEvent: The event to be sent. This value cannot be null.

Returns
boolean	True if the event should be sent

See also:

• ViewGroup#onRequestSendAccessibilityEvent(View, AccessibilityEvent)

performAccessibilityAction

Added in API level 16

public boolean performAccessibilityAction (View host, 
                int action, 
                Bundle args)

Performs the specified accessibility action on the view. For possible accessibility actions look at AccessibilityNodeInfo.

The default implementation behaves as View#performAccessibilityAction(int, Bundle) for the case of no accessibility delegate been set.

Parameters
host	View: This value cannot be null.
action	int: The action to perform.
args	Bundle: This value may be null.

Returns
boolean	Whether the action was performed.

See also:

• View#performAccessibilityAction(int, Bundle)

sendAccessibilityEvent

Added in API level 14

public void sendAccessibilityEvent (View host, 
                int eventType)

Sends an accessibility event of the given type. If accessibility is not enabled this method has no effect.

The default implementation behaves as View#sendAccessibilityEvent(int) for the case of no accessibility delegate been set.

Parameters
host	View: The View hosting the delegate. This value cannot be null.
eventType	int: The type of the event to send.

See also:

• View#sendAccessibilityEvent(int)

sendAccessibilityEventUnchecked

Added in API level 14

public void sendAccessibilityEventUnchecked (View host, 
                AccessibilityEvent event)

Sends an accessibility event. This method behaves exactly as sendAccessibilityEvent(android.view.View, int) but takes as an argument an empty AccessibilityEvent and does not perform a check whether accessibility is enabled.

The default implementation behaves as View#sendAccessibilityEventUnchecked(AccessibilityEvent) for the case of no accessibility delegate been set.

Parameters
host	View: The View hosting the delegate. This value cannot be null.
event	AccessibilityEvent: The event to send. This value cannot be null.

See also:

• View#sendAccessibilityEventUnchecked(AccessibilityEvent)