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 {@link AccessibilityService#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" * {@link android.content.Intent}. Failure to declare this intent will cause the system to * ignore the accessibility service. Additionally an accessibility service must request the * {@link android.Manifest.permission#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: *
*<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 {@link #SERVICE_META_DATA} and
* <{@link android.R.styleable#AccessibilityService accessibility-service}>.
*
* Note: This approach enables setting only dynamically configurable properties: * {@link AccessibilityServiceInfo#eventTypes}, * {@link AccessibilityServiceInfo#feedbackType}, * {@link AccessibilityServiceInfo#flags}, * {@link AccessibilityServiceInfo#notificationTimeout}, * {@link AccessibilityServiceInfo#packageNames} *
** For more details refer to {@link AccessibilityServiceInfo}. *
** A service can specify in its declaration that it can retrieve the active window * content which is represented as a tree of {@link AccessibilityNodeInfo}. Note that * declaring this capability requires that the service declares its configuration via * an XML resource referenced by {@link #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: * {@link AccessibilityEvent#TYPE_WINDOW_STATE_CHANGED}, * {@link AccessibilityEvent#TYPE_VIEW_HOVER_ENTER}, * {@link AccessibilityEvent#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 * {@link AccessibilityEvent#getSource() AccessibilityEvent.getSource()} of the last received * event of the above types or a previous event from the same window * (see {@link AccessibilityEvent#getWindowId() AccessibilityEvent.getWindowId()}). Invoking * this method will return an {@link 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: *
* 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.
*<{@link android.R.styleable#AccessibilityService accessibility-service}>
* tag. This is a a sample XML file configuring an 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"
* . . .
* />
*/
public static final String SERVICE_META_DATA = "android.accessibilityservice";
/**
* Action to go back.
*/
public static final int GLOBAL_ACTION_BACK = 1;
/**
* Action to go home.
*/
public static final int GLOBAL_ACTION_HOME = 2;
/**
* Action to open the recent apps.
*/
public static final int GLOBAL_ACTION_RECENTS = 3;
/**
* Action to open the notifications.
*/
public static final int GLOBAL_ACTION_NOTIFICATIONS = 4;
/**
* Action to open the quick settings.
*/
public static final int GLOBAL_ACTION_QUICK_SETTINGS = 5;
private static final String LOG_TAG = "AccessibilityService";
/**
* @hide
*/
public interface Callbacks {
public void onAccessibilityEvent(AccessibilityEvent event);
public void onInterrupt();
public void onServiceConnected();
public void onSetConnectionId(int connectionId);
public boolean onGesture(int gestureId);
public boolean onKeyEvent(KeyEvent event);
}
private int mConnectionId;
private AccessibilityServiceInfo mInfo;
/**
* Callback for {@link android.view.accessibility.AccessibilityEvent}s.
*
* @param event An event.
*/
public abstract void onAccessibilityEvent(AccessibilityEvent event);
/**
* Callback for interrupting the accessibility feedback.
*/
public abstract void onInterrupt();
/**
* This method is a part of the {@link AccessibilityService} lifecycle and is
* called after the system has successfully bound to the service. If is
* convenient to use this method for setting the {@link AccessibilityServiceInfo}.
*
* @see AccessibilityServiceInfo
* @see #setServiceInfo(AccessibilityServiceInfo)
*/
protected void onServiceConnected() {
}
/**
* 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
* {@link android.accessibilityservice.AccessibilityServiceInfo#FLAG_REQUEST_TOUCH_EXPLORATION_MODE}
* flag.
*
* @param gestureId The unique id of the performed gesture.
*
* @return Whether the gesture was handled.
*
* @see #GESTURE_SWIPE_UP
* @see #GESTURE_SWIPE_UP_AND_LEFT
* @see #GESTURE_SWIPE_UP_AND_DOWN
* @see #GESTURE_SWIPE_UP_AND_RIGHT
* @see #GESTURE_SWIPE_DOWN
* @see #GESTURE_SWIPE_DOWN_AND_LEFT
* @see #GESTURE_SWIPE_DOWN_AND_UP
* @see #GESTURE_SWIPE_DOWN_AND_RIGHT
* @see #GESTURE_SWIPE_LEFT
* @see #GESTURE_SWIPE_LEFT_AND_UP
* @see #GESTURE_SWIPE_LEFT_AND_RIGHT
* @see #GESTURE_SWIPE_LEFT_AND_DOWN
* @see #GESTURE_SWIPE_RIGHT
* @see #GESTURE_SWIPE_RIGHT_AND_UP
* @see #GESTURE_SWIPE_RIGHT_AND_LEFT
* @see #GESTURE_SWIPE_RIGHT_AND_DOWN
*/
protected boolean onGesture(int gestureId) {
return false;
}
/**
* 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. *
* * @param event The event to be processed. * @return If true then the event will be consumed and not delivered to * applications, otherwise it will be delivered as usual. */ protected boolean onKeyEvent(KeyEvent event) { return false; } /** * Gets the root node in the currently active window if this service * can retrieve window content. * * @return The root node if this service can retrieve window content. */ public AccessibilityNodeInfo getRootInActiveWindow() { return AccessibilityInteractionClient.getInstance().getRootInActiveWindow(mConnectionId); } /** * 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. * * @param action The action to perform. * @return Whether the action was successfully performed. * * @see #GLOBAL_ACTION_BACK * @see #GLOBAL_ACTION_HOME * @see #GLOBAL_ACTION_NOTIFICATIONS * @see #GLOBAL_ACTION_RECENTS */ public final boolean performGlobalAction(int action) { IAccessibilityServiceConnection connection = AccessibilityInteractionClient.getInstance().getConnection(mConnectionId); if (connection != null) { try { return connection.performGlobalAction(action); } catch (RemoteException re) { Log.w(LOG_TAG, "Error while calling performGlobalAction", re); } } return false; } /** * Gets the an {@link AccessibilityServiceInfo} describing this * {@link AccessibilityService}. This method is useful if one wants * to change some of the dynamically configurable properties at * runtime. * * @return The accessibility service info. * * @see AccessibilityServiceInfo */ public final AccessibilityServiceInfo getServiceInfo() { IAccessibilityServiceConnection connection = AccessibilityInteractionClient.getInstance().getConnection(mConnectionId); if (connection != null) { try { return connection.getServiceInfo(); } catch (RemoteException re) { Log.w(LOG_TAG, "Error while getting AccessibilityServiceInfo", re); } } return null; } /** * Sets the {@link 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. * * @param info The info. */ public final void setServiceInfo(AccessibilityServiceInfo info) { mInfo = info; sendServiceInfo(); } /** * Sets the {@link AccessibilityServiceInfo} for this service if the latter is * properly set and there is an {@link IAccessibilityServiceConnection} to the * AccessibilityManagerService. */ private void sendServiceInfo() { IAccessibilityServiceConnection connection = AccessibilityInteractionClient.getInstance().getConnection(mConnectionId); if (mInfo != null && connection != null) { try { connection.setServiceInfo(mInfo); mInfo = null; AccessibilityInteractionClient.getInstance().clearCache(); } catch (RemoteException re) { Log.w(LOG_TAG, "Error while setting AccessibilityServiceInfo", re); } } } /** * Implement to return the implementation of the internal accessibility * service interface. */ @Override public final IBinder onBind(Intent intent) { return new IAccessibilityServiceClientWrapper(this, getMainLooper(), new Callbacks() { @Override public void onServiceConnected() { AccessibilityService.this.onServiceConnected(); } @Override public void onInterrupt() { AccessibilityService.this.onInterrupt(); } @Override public void onAccessibilityEvent(AccessibilityEvent event) { AccessibilityService.this.onAccessibilityEvent(event); } @Override public void onSetConnectionId( int connectionId) { mConnectionId = connectionId; } @Override public boolean onGesture(int gestureId) { return AccessibilityService.this.onGesture(gestureId); } @Override public boolean onKeyEvent(KeyEvent event) { return AccessibilityService.this.onKeyEvent(event); } }); } /** * Implements the internal {@link IAccessibilityServiceClient} interface to convert * incoming calls to it back to calls on an {@link AccessibilityService}. * * @hide */ public static class IAccessibilityServiceClientWrapper extends IAccessibilityServiceClient.Stub implements HandlerCaller.Callback { static final int NO_ID = -1; private static final int DO_SET_SET_CONNECTION = 10; private static final int DO_ON_INTERRUPT = 20; private static final int DO_ON_ACCESSIBILITY_EVENT = 30; private static final int DO_ON_GESTURE = 40; private static final int DO_CLEAR_ACCESSIBILITY_NODE_INFO_CACHE = 50; private static final int DO_ON_KEY_EVENT = 60; private final HandlerCaller mCaller; private final Callbacks mCallback; private int mConnectionId; public IAccessibilityServiceClientWrapper(Context context, Looper looper, Callbacks callback) { mCallback = callback; mCaller = new HandlerCaller(context, looper, this, true /*asyncHandler*/); } public void setConnection(IAccessibilityServiceConnection connection, int connectionId) { Message message = mCaller.obtainMessageIO(DO_SET_SET_CONNECTION, connectionId, connection); mCaller.sendMessage(message); } public void onInterrupt() { Message message = mCaller.obtainMessage(DO_ON_INTERRUPT); mCaller.sendMessage(message); } public void onAccessibilityEvent(AccessibilityEvent event) { Message message = mCaller.obtainMessageO(DO_ON_ACCESSIBILITY_EVENT, event); mCaller.sendMessage(message); } public void onGesture(int gestureId) { Message message = mCaller.obtainMessageI(DO_ON_GESTURE, gestureId); mCaller.sendMessage(message); } public void clearAccessibilityNodeInfoCache() { Message message = mCaller.obtainMessage(DO_CLEAR_ACCESSIBILITY_NODE_INFO_CACHE); mCaller.sendMessage(message); } @Override public void onKeyEvent(KeyEvent event, int sequence) { Message message = mCaller.obtainMessageIO(DO_ON_KEY_EVENT, sequence, event); mCaller.sendMessage(message); } public void executeMessage(Message message) { switch (message.what) { case DO_ON_ACCESSIBILITY_EVENT: { AccessibilityEvent event = (AccessibilityEvent) message.obj; if (event != null) { AccessibilityInteractionClient.getInstance().onAccessibilityEvent(event); mCallback.onAccessibilityEvent(event); event.recycle(); } } return; case DO_ON_INTERRUPT: { mCallback.onInterrupt(); } return; case DO_SET_SET_CONNECTION: { mConnectionId = message.arg1; IAccessibilityServiceConnection connection = (IAccessibilityServiceConnection) message.obj; if (connection != null) { AccessibilityInteractionClient.getInstance().addConnection(mConnectionId, connection); mCallback.onSetConnectionId(mConnectionId); mCallback.onServiceConnected(); } else { AccessibilityInteractionClient.getInstance().removeConnection(mConnectionId); AccessibilityInteractionClient.getInstance().clearCache(); mCallback.onSetConnectionId(AccessibilityInteractionClient.NO_ID); } } return; case DO_ON_GESTURE: { final int gestureId = message.arg1; mCallback.onGesture(gestureId); } return; case DO_CLEAR_ACCESSIBILITY_NODE_INFO_CACHE: { AccessibilityInteractionClient.getInstance().clearCache(); } return; case DO_ON_KEY_EVENT: { KeyEvent event = (KeyEvent) message.obj; try { IAccessibilityServiceConnection connection = AccessibilityInteractionClient .getInstance().getConnection(mConnectionId); if (connection != null) { final boolean result = mCallback.onKeyEvent(event); final int sequence = message.arg1; try { connection.setOnKeyEventResult(result, sequence); } catch (RemoteException re) { /* ignore */ } } } finally { event.recycle(); } } return; default : Log.w(LOG_TAG, "Unknown message type " + message.what); } } } }