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diff --git a/core/java/android/accessibilityservice/AccessibilityButtonController.java b/core/java/android/accessibilityservice/AccessibilityButtonController.java
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+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.accessibilityservice;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.os.Handler;
+import android.os.RemoteException;
+import android.util.ArrayMap;
+import android.util.Slog;
+
+/**
+ * Controller for the accessibility button within the system's navigation area
+ * <p>
+ * This class may be used to query the accessibility button's state and register
+ * callbacks for interactions with and state changes to the accessibility button when
+ * {@link AccessibilityServiceInfo#FLAG_REQUEST_ACCESSIBILITY_BUTTON} is set.
+ * </p>
+ * <p>
+ * <strong>Note:</strong> This class and
+ * {@link AccessibilityServiceInfo#FLAG_REQUEST_ACCESSIBILITY_BUTTON} should not be used as
+ * the sole means for offering functionality to users via an {@link AccessibilityService}.
+ * Some device implementations may choose not to provide a software-rendered system
+ * navigation area, making this affordance permanently unavailable.
+ * </p>
+ * <p>
+ * <strong>Note:</strong> On device implementations where the accessibility button is
+ * supported, it may not be available at all times, such as when a foreground application uses
+ * {@link android.view.View#SYSTEM_UI_FLAG_HIDE_NAVIGATION}. A user may also choose to assign
+ * this button to another accessibility service or feature. In each of these cases, a
+ * registered {@link AccessibilityButtonCallback}'s
+ * {@link AccessibilityButtonCallback#onAvailabilityChanged(AccessibilityButtonController, boolean)}
+ * method will be invoked to provide notifications of changes in the accessibility button's
+ * availability to the registering service.
+ * </p>
+ */
+public final class AccessibilityButtonController {
+    private static final String LOG_TAG = "A11yButtonController";
+
+    private final IAccessibilityServiceConnection mServiceConnection;
+    private final Object mLock;
+    private ArrayMap<AccessibilityButtonCallback, Handler> mCallbacks;
+
+    AccessibilityButtonController(@NonNull IAccessibilityServiceConnection serviceConnection) {
+        mServiceConnection = serviceConnection;
+        mLock = new Object();
+    }
+
+    /**
+     * Retrieves whether the accessibility button in the system's navigation area is
+     * available to the calling service.
+     * <p>
+     * <strong>Note:</strong> If the service is not yet connected (e.g.
+     * {@link AccessibilityService#onServiceConnected()} has not yet been called) or the
+     * service has been disconnected, this method will have no effect and return {@code false}.
+     * </p>
+     *
+     * @return {@code true} if the accessibility button in the system's navigation area is
+     * available to the calling service, {@code false} otherwise
+     */
+    public boolean isAccessibilityButtonAvailable() {
+        try {
+            return mServiceConnection.isAccessibilityButtonAvailable();
+        } catch (RemoteException re) {
+            Slog.w(LOG_TAG, "Failed to get accessibility button availability.", re);
+            re.rethrowFromSystemServer();
+            return false;
+        }
+    }
+
+    /**
+     * Registers the provided {@link AccessibilityButtonCallback} for interaction and state
+     * changes callbacks related to the accessibility button.
+     *
+     * @param callback the callback to add, must be non-null
+     */
+    public void registerAccessibilityButtonCallback(@NonNull AccessibilityButtonCallback callback) {
+        registerAccessibilityButtonCallback(callback, null);
+    }
+
+    /**
+     * Registers the provided {@link AccessibilityButtonCallback} for interaction and state
+     * change callbacks related to the accessibility button. The callback will occur on the
+     * specified {@link Handler}'s thread, or on the services's main thread if the handler is
+     * {@code null}.
+     *
+     * @param callback the callback to add, must be non-null
+     * @param handler the handler on which to callback should execute, or {@code null} to
+     *                execute on the service's main thread
+     */
+    public void registerAccessibilityButtonCallback(@NonNull AccessibilityButtonCallback callback,
+            @Nullable Handler handler) {
+        synchronized (mLock) {
+            if (mCallbacks == null) {
+                mCallbacks = new ArrayMap<>();
+            }
+
+            mCallbacks.put(callback, handler);
+        }
+    }
+
+    /**
+     * Unregisters the provided {@link AccessibilityButtonCallback} for interaction and state
+     * change callbacks related to the accessibility button.
+     *
+     * @param callback the callback to remove, must be non-null
+     */
+    public void unregisterAccessibilityButtonCallback(
+            @NonNull AccessibilityButtonCallback callback) {
+        synchronized (mLock) {
+            if (mCallbacks == null) {
+                return;
+            }
+
+            final int keyIndex = mCallbacks.indexOfKey(callback);
+            final boolean hasKey = keyIndex >= 0;
+            if (hasKey) {
+                mCallbacks.removeAt(keyIndex);
+            }
+        }
+    }
+
+    /**
+     * Dispatches the accessibility button click to any registered callbacks. This should
+     * be called on the service's main thread.
+     */
+    void dispatchAccessibilityButtonClicked() {
+        final ArrayMap<AccessibilityButtonCallback, Handler> entries;
+        synchronized (mLock) {
+            if (mCallbacks == null || mCallbacks.isEmpty()) {
+                Slog.w(LOG_TAG, "Received accessibility button click with no callbacks!");
+                return;
+            }
+
+            // Callbacks may remove themselves. Perform a shallow copy to avoid concurrent
+            // modification.
+            entries = new ArrayMap<>(mCallbacks);
+        }
+
+        for (int i = 0, count = entries.size(); i < count; i++) {
+            final AccessibilityButtonCallback callback = entries.keyAt(i);
+            final Handler handler = entries.valueAt(i);
+            if (handler != null) {
+                handler.post(() -> callback.onClicked(this));
+            } else {
+                // We're already on the main thread, just run the callback.
+                callback.onClicked(this);
+            }
+        }
+    }
+
+    /**
+     * Dispatches the accessibility button availability changes to any registered callbacks.
+     * This should be called on the service's main thread.
+     */
+    void dispatchAccessibilityButtonAvailabilityChanged(boolean available) {
+        final ArrayMap<AccessibilityButtonCallback, Handler> entries;
+        synchronized (mLock) {
+            if (mCallbacks == null || mCallbacks.isEmpty()) {
+                Slog.w(LOG_TAG,
+                        "Received accessibility button availability change with no callbacks!");
+                return;
+            }
+
+            // Callbacks may remove themselves. Perform a shallow copy to avoid concurrent
+            // modification.
+            entries = new ArrayMap<>(mCallbacks);
+        }
+
+        for (int i = 0, count = entries.size(); i < count; i++) {
+            final AccessibilityButtonCallback callback = entries.keyAt(i);
+            final Handler handler = entries.valueAt(i);
+            if (handler != null) {
+                handler.post(() -> callback.onAvailabilityChanged(this, available));
+            } else {
+                // We're already on the main thread, just run the callback.
+                callback.onAvailabilityChanged(this, available);
+            }
+        }
+    }
+
+    /**
+     * Callback for interaction with and changes to state of the accessibility button
+     * within the system's navigation area.
+     */
+    public static abstract class AccessibilityButtonCallback {
+
+        /**
+         * Called when the accessibility button in the system's navigation area is clicked.
+         *
+         * @param controller the controller used to register for this callback
+         */
+        public void onClicked(AccessibilityButtonController controller) {}
+
+        /**
+         * Called when the availability of the accessibility button in the system's
+         * navigation area has changed. The accessibility button may become unavailable
+         * because the device shopped showing the button, the button was assigned to another
+         * service, or for other reasons.
+         *
+         * @param controller the controller used to register for this callback
+         * @param available {@code true} if the accessibility button is available to this
+         *                  service, {@code false} otherwise
+         */
+        public void onAvailabilityChanged(AccessibilityButtonController controller,
+                boolean available) {
+        }
+    }
+}