java.lang.Object | ||||
↳ | android.content.Context | |||
↳ | android.content.ContextWrapper | |||
↳ | android.app.Service | |||
↳ | android.accessibilityservice.AccessibilityService |
An accessibility service runs in the background and receives callbacks by the system
when AccessibilityEvent
s 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 extending this
class and implementing its abstract methods.
For more information about creating AccessibilityServices, read the Accessibility developer guide.
The lifecycle of an accessibility service is managed exclusively by the system and
follows the established service life cycle. Additionally, starting or stopping an
accessibility service is triggered exclusively by an explicit user action through
enabling or disabling it in the device settings. After the system binds to a service it
calls onServiceConnected()
. This method can be
overriden by clients that want to perform post binding setup.
An accessibility is declared as any other service in an AndroidManifest.xml but it
must also specify that it handles the "android.accessibilityservice.AccessibilityService"
Intent
. Failure to declare this intent will cause the system to
ignore the accessibility service. Additionally an accessibility service must request the
BIND_ACCESSIBILITY_SERVICE
permission to ensure
that only the system
can bind to it. Failure to declare this intent will cause the system to ignore the
accessibility service. Following is an example declaration:
<service android:name=".MyAccessibilityService" android:permission="android.permission.BIND_ACCESSIBILITY_SERVICE"> <intent-filter> <action android:name="android.accessibilityservice.AccessibilityService" /> </intent-filter> . . . </service>
An accessibility service can be configured to receive specific types of accessibility events, listen only to specific packages, get events from each type only once in a given time frame, retrieve window content, specify a settings activity, etc.
There are two approaches for configuring an accessibility service:
meta-data
entry in the manifest when declaring
the service. A service declaration with a meta-data tag is presented below:
<service android:name=".MyAccessibilityService"> <intent-filter> <action android:name="android.accessibilityservice.AccessibilityService" /> </intent-filter> <meta-data android:name="android.accessibilityservice" android:resource="@xml/accessibilityservice" /> </service>
Note: This approach enables setting all properties.
For more details refer to SERVICE_META_DATA
and
<
.
accessibility-service
>
setServiceInfo(AccessibilityServiceInfo)
. Note
that this method can be called any time to dynamically change the service configuration.
Note: This approach enables setting only dynamically configurable properties:
eventTypes
,
feedbackType
,
flags
,
notificationTimeout
,
packageNames
For more details refer to AccessibilityServiceInfo
.
A service can specify in its declaration that it can retrieve the active window
content which is represented as a tree of AccessibilityNodeInfo
. Note that
declaring this capability requires that the service declares its configuration via
an XML resource referenced by SERVICE_META_DATA
.
For security purposes an accessibility service can retrieve only the content of the
currently active window. The currently active window is defined as the window from
which was fired the last event of the following types:
TYPE_WINDOW_STATE_CHANGED
,
TYPE_VIEW_HOVER_ENTER
,
TYPE_VIEW_HOVER_EXIT
,
In other words, the last window that was shown or the last window that the user has touched
during touch exploration.
The entry point for retrieving window content is through calling
AccessibilityEvent.getSource()
of the last received
event of the above types or a previous event from the same window
(see AccessibilityEvent.getWindowId()
). Invoking
this method will return an AccessibilityNodeInfo
that can be used to traverse the
window content which represented as a tree of such objects.
Note An accessibility service may have requested to be notified for a subset of the event types, thus be unaware that the active window has changed. Therefore accessibility service that would like to retrieve window content should:
getWindowId()
of the last received event and
compare this with the getWindowId()
before calling retrieval
methods on the latter.
AccessibilityNodeInfo
may fail since the
active window has changed and the service did not get the accessibility event yet. Note
that it is possible to have a retrieval method failing even adopting the strategy
specified in the previous bullet because the accessibility event dispatch is asynchronous
and crosses process boundaries.
For each feedback type only one accessibility service is notified. Services are notified in the order of registration. Hence, if two services are registered for the same feedback type in the same package the first one wins. It is possible however, to register a service as the default one for a given feedback type. In such a case this service is invoked if no other service was interested in the event. In other words, default services do not compete with other services and are notified last regardless of the registration order. This enables "generic" accessibility services that work reasonably well with most applications to coexist with "polished" ones that are targeted for specific applications.
Note: The event notification timeout is useful to avoid propagating events to the client too frequently since this is accomplished via an expensive interprocess call. One can think of the timeout as a criteria to determine when event generation has settled down.
TYPE_VIEW_CLICKED
TYPE_VIEW_LONG_CLICKED
TYPE_VIEW_FOCUSED
TYPE_VIEW_SELECTED
TYPE_VIEW_TEXT_CHANGED
TYPE_WINDOW_STATE_CHANGED
TYPE_NOTIFICATION_STATE_CHANGED
TYPE_TOUCH_EXPLORATION_GESTURE_START
TYPE_TOUCH_EXPLORATION_GESTURE_END
TYPE_VIEW_HOVER_ENTER
TYPE_VIEW_HOVER_EXIT
TYPE_VIEW_SCROLLED
TYPE_VIEW_TEXT_SELECTION_CHANGED
TYPE_WINDOW_CONTENT_CHANGED
TYPE_ANNOUNCEMENT
TYPE_GESTURE_DETECTION_START
TYPE_GESTURE_DETECTION_END
TYPE_TOUCH_INTERACTION_START
TYPE_TOUCH_INTERACTION_END
TYPE_VIEW_ACCESSIBILITY_FOCUSED
TYPE_WINDOWS_CHANGED
TYPE_VIEW_ACCESSIBILITY_FOCUS_CLEARED
Constants | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
int | GESTURE_SWIPE_DOWN | The user has performed a swipe down gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_DOWN_AND_LEFT | The user has performed an down and left gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_DOWN_AND_RIGHT | The user has performed an down and right gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_DOWN_AND_UP | The user has performed a swipe down and up gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_LEFT | The user has performed a swipe left gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_LEFT_AND_DOWN | The user has performed a left and down gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_LEFT_AND_RIGHT | The user has performed a swipe left and right gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_LEFT_AND_UP | The user has performed a left and up gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_RIGHT | The user has performed a swipe right gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_RIGHT_AND_DOWN | The user has performed a right and down gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_RIGHT_AND_LEFT | The user has performed a swipe right and left gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_RIGHT_AND_UP | The user has performed a right and up gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_UP | The user has performed a swipe up gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_UP_AND_DOWN | The user has performed a swipe up and down gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_UP_AND_LEFT | The user has performed an up and left gesture on the touch screen. | |||||||||
int | GESTURE_SWIPE_UP_AND_RIGHT | The user has performed an up and right gesture on the touch screen. | |||||||||
int | GLOBAL_ACTION_BACK | Action to go back. | |||||||||
int | GLOBAL_ACTION_HOME | Action to go home. | |||||||||
int | GLOBAL_ACTION_NOTIFICATIONS | Action to open the notifications. | |||||||||
int | GLOBAL_ACTION_QUICK_SETTINGS | Action to open the quick settings. | |||||||||
int | GLOBAL_ACTION_RECENTS | Action to open the recent apps. | |||||||||
String | SERVICE_INTERFACE | The Intent that must be declared as handled by the service. |
|||||||||
String | SERVICE_META_DATA | Name under which an AccessibilityService component publishes information about itself. |
[Expand]
Inherited Constants | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
From class
android.app.Service
| |||||||||||
From class
android.content.Context
| |||||||||||
From interface
android.content.ComponentCallbacks2
|
Public Constructors | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Public Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Find the view that has the specified focus type.
| |||||||||||
Gets the root node in the currently active window if this service
can retrieve window content.
| |||||||||||
Gets the an
AccessibilityServiceInfo describing this
AccessibilityService . | |||||||||||
Gets the windows on the screen.
| |||||||||||
Callback for
AccessibilityEvent s. | |||||||||||
Implement to return the implementation of the internal accessibility
service interface.
| |||||||||||
Callback for interrupting the accessibility feedback.
| |||||||||||
Performs a global action.
| |||||||||||
Sets the
AccessibilityServiceInfo that describes this service. |
Protected Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Called by the system when the user performs a specific gesture on the
touch screen.
| |||||||||||
Callback that allows an accessibility service to observe the key events
before they are passed to the rest of the system.
| |||||||||||
This method is a part of the
AccessibilityService lifecycle and is
called after the system has successfully bound to the service. |
[Expand]
Inherited Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
From class
android.app.Service
| |||||||||||
From class
android.content.ContextWrapper
| |||||||||||
From class
android.content.Context
| |||||||||||
From class
java.lang.Object
| |||||||||||
From interface
android.content.ComponentCallbacks
| |||||||||||
From interface
android.content.ComponentCallbacks2
|
The user has performed a swipe down gesture on the touch screen.
The user has performed an down and left gesture on the touch screen.
The user has performed an down and right gesture on the touch screen.
The user has performed a swipe down and up gesture on the touch screen.
The user has performed a swipe left gesture on the touch screen.
The user has performed a left and down gesture on the touch screen.
The user has performed a swipe left and right gesture on the touch screen.
The user has performed a left and up gesture on the touch screen.
The user has performed a swipe right gesture on the touch screen.
The user has performed a right and down gesture on the touch screen.
The user has performed a swipe right and left gesture on the touch screen.
The user has performed a right and up gesture on the touch screen.
The user has performed a swipe up gesture on the touch screen.
The user has performed a swipe up and down gesture on the touch screen.
The user has performed an up and left gesture on the touch screen.
The user has performed an up and right gesture on the touch screen.
Action to go back.
Action to go home.
Action to open the notifications.
Action to open the quick settings.
Action to open the recent apps.
The Intent
that must be declared as handled by the service.
Name under which an AccessibilityService component publishes information
about itself. This meta-data must reference an XML resource containing an
<
tag. This is a a sample XML file configuring an accessibility service:
accessibility-service
>
<accessibility-service android:accessibilityEventTypes="typeViewClicked|typeViewFocused" android:packageNames="foo.bar, foo.baz" android:accessibilityFeedbackType="feedbackSpoken" android:notificationTimeout="100" android:accessibilityFlags="flagDefault" android:settingsActivity="foo.bar.TestBackActivity" android:canRetrieveWindowContent="true" android:canRequestTouchExplorationMode="true" android:canRequestEnhancedWebAccessibility="true" . . . />
Find the view that has the specified focus type. The search is performed across all windows.
Note: In order to access the windows your service has
to declare the capability to retrieve window content by setting the
AccessibilityService_canRetrieveWindowContent
property in its meta-data. For details refer to SERVICE_META_DATA
.
Also the service has to opt-in to retrieve the interactive windows by
setting the FLAG_RETRIEVE_INTERACTIVE_WINDOWS
flag.Otherwise, the search will be performed only in the active window.
focus | The focus to find. One of FOCUS_INPUT or
FOCUS_ACCESSIBILITY . |
---|
Gets the root node in the currently active window if this service can retrieve window content. The active window is the one that the user is currently touching or the window with input focus, if the user is not touching any window.
Note: In order to access the root node your service has
to declare the capability to retrieve window content by setting the
AccessibilityService_canRetrieveWindowContent
property in its meta-data. For details refer to SERVICE_META_DATA
.
Gets the an AccessibilityServiceInfo
describing this
AccessibilityService
. This method is useful if one wants
to change some of the dynamically configurable properties at
runtime.
Gets the windows on the screen. This method returns only the windows that a sighted user can interact with, as opposed to all windows. For example, if there is a modal dialog shown and the user cannot touch anything behind it, then only the modal window will be reported (assuming it is the top one). For convenience the returned windows are ordered in a descending layer order, which is the windows that are higher in the Z-order are reported first.
Note: In order to access the windows your service has
to declare the capability to retrieve window content by setting the
AccessibilityService_canRetrieveWindowContent
property in its meta-data. For details refer to SERVICE_META_DATA
.
Also the service has to opt-in to retrieve the interactive windows by
setting the FLAG_RETRIEVE_INTERACTIVE_WINDOWS
flag.
Callback for AccessibilityEvent
s.
event | An event. |
---|
Implement to return the implementation of the internal accessibility service interface.
intent | The Intent that was used to bind to this service,
as given to Context.bindService . Note that any extras that were included with
the Intent at that point will not be seen here. |
---|
Callback for interrupting the accessibility feedback.
Performs a global action. Such an action can be performed at any moment regardless of the current application or user location in that application. For example going back, going home, opening recents, etc.
action | The action to perform. |
---|
Sets the AccessibilityServiceInfo
that describes this service.
Note: You can call this method any time but the info will be picked up after the system has bound to this service and when this method is called thereafter.
info | The info. |
---|
Called by the system when the user performs a specific gesture on the
touch screen.
Note: To receive gestures an accessibility service must
request that the device is in touch exploration mode by setting the
FLAG_REQUEST_TOUCH_EXPLORATION_MODE
flag.
gestureId | The unique id of the performed gesture. |
---|
GESTURE_SWIPE_UP
GESTURE_SWIPE_UP_AND_LEFT
GESTURE_SWIPE_UP_AND_DOWN
GESTURE_SWIPE_UP_AND_RIGHT
GESTURE_SWIPE_DOWN
GESTURE_SWIPE_DOWN_AND_LEFT
GESTURE_SWIPE_DOWN_AND_UP
GESTURE_SWIPE_DOWN_AND_RIGHT
GESTURE_SWIPE_LEFT
GESTURE_SWIPE_LEFT_AND_UP
GESTURE_SWIPE_LEFT_AND_RIGHT
GESTURE_SWIPE_LEFT_AND_DOWN
GESTURE_SWIPE_RIGHT
GESTURE_SWIPE_RIGHT_AND_UP
GESTURE_SWIPE_RIGHT_AND_LEFT
GESTURE_SWIPE_RIGHT_AND_DOWN
Callback that allows an accessibility service to observe the key events before they are passed to the rest of the system. This means that the events are first delivered here before they are passed to the device policy, the input method, or applications.
Note: It is important that key events are handled in such a way that the event stream that would be passed to the rest of the system is well-formed. For example, handling the down event but not the up event and vice versa would generate an inconsistent event stream.
Note: The key events delivered in this method are copies and modifying them will have no effect on the events that will be passed to the system. This method is intended to perform purely filtering functionality.
event | The event to be processed. |
---|
This method is a part of the AccessibilityService
lifecycle and is
called after the system has successfully bound to the service. If is
convenient to use this method for setting the AccessibilityServiceInfo
.