Android example source code file (AccessibilityManager.java)

This example Android source code file (AccessibilityManager.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

accessibilitymanager, accessibilityservices, android, content, did, do_set_enabled, error, iaccessibilitymanager, illegalstateexception, installed, list, logv, myhandler, object, os, remoteexception, requested, util, utilities, utils

The AccessibilityManager.java Android example source code

/*
 * Copyright (C) 2009 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.view.accessibility;

import static android.util.Config.LOGV;

import android.content.Context;
import android.content.pm.ServiceInfo;
import android.os.Binder;
import android.os.Handler;
import android.os.IBinder;
import android.os.Looper;
import android.os.Message;
import android.os.RemoteException;
import android.os.ServiceManager;
import android.os.SystemClock;
import android.util.Log;

import java.util.Collections;
import java.util.List;

/**
 * System level service that serves as an event dispatch for {@link AccessibilityEvent}s.
 * Such events are generated when something notable happens in the user interface,
 * for example an {@link android.app.Activity} starts, the focus or selection of a
 * {@link android.view.View} changes etc. Parties interested in handling accessibility
 * events implement and register an accessibility service which extends
 * {@link android.accessibilityservice.AccessibilityService}.
 *
 * @see AccessibilityEvent
 * @see android.accessibilityservice.AccessibilityService
 * @see android.content.Context#getSystemService
 */
public final class AccessibilityManager {
    private static final String LOG_TAG = "AccessibilityManager";

    static final Object sInstanceSync = new Object();

    private static AccessibilityManager sInstance;

    private static final int DO_SET_ENABLED = 10;

    final IAccessibilityManager mService;

    final Handler mHandler;

    boolean mIsEnabled;

    final IAccessibilityManagerClient.Stub mClient = new IAccessibilityManagerClient.Stub() {
        public void setEnabled(boolean enabled) {
            mHandler.obtainMessage(DO_SET_ENABLED, enabled ? 1 : 0, 0).sendToTarget();
        }
    };

    class MyHandler extends Handler {

        MyHandler(Looper mainLooper) {
            super(mainLooper);
        }

        @Override
        public void handleMessage(Message message) {
            switch (message.what) {
                case DO_SET_ENABLED :
                    synchronized (mHandler) {
                        mIsEnabled = (message.arg1 == 1);
                    }
                    return;
                default :
                    Log.w(LOG_TAG, "Unknown message type: " + message.what);
            }
        }
    }

    /**
     * Get an AccessibilityManager instance (create one if necessary).
     *
     * @hide
     */
    public static AccessibilityManager getInstance(Context context) {
        synchronized (sInstanceSync) {
            if (sInstance == null) {
                sInstance = new AccessibilityManager(context);
            }
        }
        return sInstance;
    }

    /**
     * Create an instance.
     *
     * @param context A {@link Context}.
     */
    private AccessibilityManager(Context context) {
        mHandler = new MyHandler(context.getMainLooper());
        IBinder iBinder = ServiceManager.getService(Context.ACCESSIBILITY_SERVICE);
        mService = IAccessibilityManager.Stub.asInterface(iBinder);
        try {
            mService.addClient(mClient);
        } catch (RemoteException re) {
            Log.e(LOG_TAG, "AccessibilityManagerService is dead", re);
        }
    }

    /**
     * Returns if the {@link AccessibilityManager} is enabled.
     *
     * @return True if this {@link AccessibilityManager} is enabled, false otherwise.
     */
    public boolean isEnabled() {
        synchronized (mHandler) {
            return mIsEnabled;
        }
    }

    /**
     * Sends an {@link AccessibilityEvent}. If this {@link AccessibilityManager} is not
     * enabled the call is a NOOP.
     *
     * @param event The {@link AccessibilityEvent}.
     *
     * @throws IllegalStateException if a client tries to send an {@link AccessibilityEvent}
     *         while accessibility is not enabled.
     */
    public void sendAccessibilityEvent(AccessibilityEvent event) {
        if (!mIsEnabled) {
            throw new IllegalStateException("Accessibility off. Did you forget to check that?");
        }
        boolean doRecycle = false;
        try {
            event.setEventTime(SystemClock.uptimeMillis());
            // it is possible that this manager is in the same process as the service but
            // client using it is called through Binder from another process. Example: MMS
            // app adds a SMS notification and the NotificationManagerService calls this method
            long identityToken = Binder.clearCallingIdentity();
            doRecycle = mService.sendAccessibilityEvent(event);
            Binder.restoreCallingIdentity(identityToken);
            if (LOGV) {
                Log.i(LOG_TAG, event + " sent");
            }
        } catch (RemoteException re) {
            Log.e(LOG_TAG, "Error during sending " + event + " ", re);
        } finally {
            if (doRecycle) {
                event.recycle();
            }
        }
    }

    /**
     * Requests interruption of the accessibility feedback from all accessibility services.
     */
    public void interrupt() {
        if (!mIsEnabled) {
            throw new IllegalStateException("Accessibility off. Did you forget to check that?");
        }
        try {
            mService.interrupt();
            if (LOGV) {
                Log.i(LOG_TAG, "Requested interrupt from all services");
            }
        } catch (RemoteException re) {
            Log.e(LOG_TAG, "Error while requesting interrupt from all services. ", re);
        }
    }

    /**
     * Returns the {@link ServiceInfo}s of the installed accessibility services.
     *
     * @return An unmodifiable list with {@link ServiceInfo}s.
     */
    public List<ServiceInfo> getAccessibilityServiceList() {
        List<ServiceInfo> services = null;
        try {
            services = mService.getAccessibilityServiceList();
            if (LOGV) {
                Log.i(LOG_TAG, "Installed AccessibilityServices " + services);
            }
        } catch (RemoteException re) {
            Log.e(LOG_TAG, "Error while obtaining the installed AccessibilityServices. ", re);
        }
        return Collections.unmodifiableList(services);
    }
}