Android APIs
Added in API level 4
package

android.accessibilityservice

The classes in this package are used for development of accessibility service that provide alternative or augmented feedback to the user.

An AccessibilityService runs in the background and receives callbacks by the system when AccessibilityEvents are fired. Such events denote some state transition in the user interface, for example, the focus has changed, a button has been clicked, etc. Such a service can optionally request the capability for querying the content of the active window. Development of an accessibility service requires extends this class and implements its abstract methods.

An AccessibilityServiceInfo describes an AccessibilityService. The system notifies an AccessibilityService for AccessibilityEvents according to the information encapsulated in this class.

Classes

AccessibilityService An accessibility service runs in the background and receives callbacks by the system when AccessibilityEvents are fired. 
AccessibilityServiceInfo This class describes an AccessibilityService