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      1 /*
      2  * Copyright (C) 2009 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package android.view.accessibility;
     18 
     19 import android.accessibilityservice.AccessibilityServiceInfo;
     20 import android.content.Context;
     21 import android.content.pm.ServiceInfo;
     22 import android.view.IWindow;
     23 import android.view.View;
     24 
     25 import java.util.Collections;
     26 import java.util.List;
     27 
     28 /**
     29  * System level service that serves as an event dispatch for {@link AccessibilityEvent}s.
     30  * Such events are generated when something notable happens in the user interface,
     31  * for example an {@link android.app.Activity} starts, the focus or selection of a
     32  * {@link android.view.View} changes etc. Parties interested in handling accessibility
     33  * events implement and register an accessibility service which extends
     34  * {@link android.accessibilityservice.AccessibilityService}.
     35  *
     36  * @see AccessibilityEvent
     37  * @see android.accessibilityservice.AccessibilityService
     38  * @see android.content.Context#getSystemService
     39  */
     40 public final class AccessibilityManager {
     41     private static AccessibilityManager sInstance = new AccessibilityManager();
     42 
     43     /**
     44      * Listener for the accessibility state.
     45      */
     46     public interface AccessibilityStateChangeListener {
     47 
     48         /**
     49          * Called back on change in the accessibility state.
     50          *
     51          * @param enabled Whether accessibility is enabled.
     52          */
     53         public void onAccessibilityStateChanged(boolean enabled);
     54     }
     55 
     56     /**
     57      * Get an AccessibilityManager instance (create one if necessary).
     58      *
     59      * @hide
     60      */
     61     public static AccessibilityManager getInstance(Context context) {
     62         return sInstance;
     63     }
     64 
     65     /**
     66      * Create an instance.
     67      *
     68      * @param context A {@link Context}.
     69      */
     70     private AccessibilityManager() {
     71     }
     72 
     73     /**
     74      * Returns if the {@link AccessibilityManager} is enabled.
     75      *
     76      * @return True if this {@link AccessibilityManager} is enabled, false otherwise.
     77      */
     78     public boolean isEnabled() {
     79         return false;
     80     }
     81 
     82     /**
     83      * Sends an {@link AccessibilityEvent}. If this {@link AccessibilityManager} is not
     84      * enabled the call is a NOOP.
     85      *
     86      * @param event The {@link AccessibilityEvent}.
     87      *
     88      * @throws IllegalStateException if a client tries to send an {@link AccessibilityEvent}
     89      *         while accessibility is not enabled.
     90      */
     91     public void sendAccessibilityEvent(AccessibilityEvent event) {
     92     }
     93 
     94     /**
     95      * Requests interruption of the accessibility feedback from all accessibility services.
     96      */
     97     public void interrupt() {
     98     }
     99 
    100     /**
    101      * Returns the {@link ServiceInfo}s of the installed accessibility services.
    102      *
    103      * @return An unmodifiable list with {@link ServiceInfo}s.
    104      */
    105     public List<ServiceInfo> getAccessibilityServiceList() {
    106         // normal implementation does this in some case, so let's do the same
    107         // (unmodifiableList wrapped around null).
    108         List<ServiceInfo> services = null;
    109         return Collections.unmodifiableList(services);
    110     }
    111 
    112     public List<AccessibilityServiceInfo> getInstalledAccessibilityServiceList() {
    113         // normal implementation does this in some case, so let's do the same
    114         // (unmodifiableList wrapped around null).
    115         List<AccessibilityServiceInfo> services = null;
    116         return Collections.unmodifiableList(services);
    117     }
    118 
    119     public boolean addAccessibilityStateChangeListener(
    120             AccessibilityStateChangeListener listener) {
    121         return true;
    122     }
    123 
    124     public boolean removeAccessibilityStateChangeListener(
    125             AccessibilityStateChangeListener listener) {
    126         return true;
    127     }
    128 
    129     public int addAccessibilityInteractionConnection(IWindow windowToken,
    130             IAccessibilityInteractionConnection connection) {
    131         return View.NO_ID;
    132     }
    133 
    134     public void removeAccessibilityInteractionConnection(IWindow windowToken) {
    135     }
    136 
    137 }
    138