core/java/android/hardware/input/InputManager.java

/*
 * Copyright (C) 2012 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.hardware.input;

import com.android.internal.util.ArrayUtils;

import android.annotation.SdkConstant;
import android.annotation.SdkConstant.SdkConstantType;
import android.content.Context;
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.Vibrator;
import android.provider.Settings;
import android.provider.Settings.SettingNotFoundException;
import android.util.Log;
import android.util.SparseArray;
import android.view.InputDevice;
import android.view.InputEvent;

import java.util.ArrayList;

/**
 * Provides information about input devices and available key layouts.
 * <p>
 * Get an instance of this class by calling
 * {@link android.content.Context#getSystemService(java.lang.String)
 * Context.getSystemService()} with the argument
 * {@link android.content.Context#INPUT_SERVICE}.
 * </p>
 */
public final class InputManager {
    private static final String TAG = "InputManager";
    private static final boolean DEBUG = false;

    private static final int MSG_DEVICE_ADDED = 1;
    private static final int MSG_DEVICE_REMOVED = 2;
    private static final int MSG_DEVICE_CHANGED = 3;

    private static InputManager sInstance;

    private final IInputManager mIm;

    // Guarded by mInputDevicesLock
    private final Object mInputDevicesLock = new Object();
    private SparseArray<InputDevice> mInputDevices;
    private InputDevicesChangedListener mInputDevicesChangedListener;
    private final ArrayList<InputDeviceListenerDelegate> mInputDeviceListeners =
            new ArrayList<InputDeviceListenerDelegate>();

    /**
     * Broadcast Action: Query available keyboard layouts.
     * <p>
     * The input manager service locates available keyboard layouts
     * by querying broadcast receivers that are registered for this action.
     * An application can offer additional keyboard layouts to the user
     * by declaring a suitable broadcast receiver in its manifest.
     * </p><p>
     * Here is an example broadcast receiver declaration that an application
     * might include in its AndroidManifest.xml to advertise keyboard layouts.
     * The meta-data specifies a resource that contains a description of each keyboard
     * layout that is provided by the application.
     * <pre><code>
     * &lt;receiver android:name=".InputDeviceReceiver"
     *         android:label="@string/keyboard_layouts_label">
     *     &lt;intent-filter>
     *         &lt;action android:name="android.hardware.input.action.QUERY_KEYBOARD_LAYOUTS" />
     *     &lt;/intent-filter>
     *     &lt;meta-data android:name="android.hardware.input.metadata.KEYBOARD_LAYOUTS"
     *             android:resource="@xml/keyboard_layouts" />
     * &lt;/receiver>
     * </code></pre>
     * </p><p>
     * In the above example, the <code>@xml/keyboard_layouts</code> resource refers to
     * an XML resource whose root element is <code>&lt;keyboard-layouts></code> that
     * contains zero or more <code>&lt;keyboard-layout></code> elements.
     * Each <code>&lt;keyboard-layout></code> element specifies the name, label, and location
     * of a key character map for a particular keyboard layout.  The label on the receiver
     * is used to name the collection of keyboard layouts provided by this receiver in the
     * keyboard layout settings.
     * <pre></code>
     * &lt;?xml version="1.0" encoding="utf-8"?>
     * &lt;keyboard-layouts xmlns:android="http://schemas.android.com/apk/res/android">
     *     &lt;keyboard-layout android:name="keyboard_layout_english_us"
     *             android:label="@string/keyboard_layout_english_us_label"
     *             android:keyboardLayout="@raw/keyboard_layout_english_us" />
     * &lt;/keyboard-layouts>
     * </p><p>
     * The <code>android:name</code> attribute specifies an identifier by which
     * the keyboard layout will be known in the package.
     * The <code>android:label</code> attributes specifies a human-readable descriptive
     * label to describe the keyboard layout in the user interface, such as "English (US)".
     * The <code>android:keyboardLayout</code> attribute refers to a
     * <a href="http://source.android.com/tech/input/key-character-map-files.html">
     * key character map</a> resource that defines the keyboard layout.
     * </p>
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String ACTION_QUERY_KEYBOARD_LAYOUTS =
            "android.hardware.input.action.QUERY_KEYBOARD_LAYOUTS";

    /**
     * Metadata Key: Keyboard layout metadata associated with
     * {@link #ACTION_QUERY_KEYBOARD_LAYOUTS}.
     * <p>
     * Specifies the resource id of a XML resource that describes the keyboard
     * layouts that are provided by the application.
     * </p>
     */
    public static final String META_DATA_KEYBOARD_LAYOUTS =
            "android.hardware.input.metadata.KEYBOARD_LAYOUTS";

    /**
     * Pointer Speed: The minimum (slowest) pointer speed (-7).
     * @hide
     */
    public static final int MIN_POINTER_SPEED = -7;

    /**
     * Pointer Speed: The maximum (fastest) pointer speed (7).
     * @hide
     */
    public static final int MAX_POINTER_SPEED = 7;

    /**
     * Pointer Speed: The default pointer speed (0).
     * @hide
     */
    public static final int DEFAULT_POINTER_SPEED = 0;

    /**
     * Input Event Injection Synchronization Mode: None.
     * Never blocks.  Injection is asynchronous and is assumed always to be successful.
     * @hide
     */
    public static final int INJECT_INPUT_EVENT_MODE_ASYNC = 0; // see InputDispatcher.h

    /**
     * Input Event Injection Synchronization Mode: Wait for result.
     * Waits for previous events to be dispatched so that the input dispatcher can
     * determine whether input event injection will be permitted based on the current
     * input focus.  Does not wait for the input event to finish being handled
     * by the application.
     * @hide
     */
    public static final int INJECT_INPUT_EVENT_MODE_WAIT_FOR_RESULT = 1;  // see InputDispatcher.h

    /**
     * Input Event Injection Synchronization Mode: Wait for finish.
     * Waits for the event to be delivered to the application and handled.
     * @hide
     */
    public static final int INJECT_INPUT_EVENT_MODE_WAIT_FOR_FINISH = 2;  // see InputDispatcher.h

    private InputManager(IInputManager im) {
        mIm = im;
    }

    /**
     * Gets an instance of the input manager.
     *
     * @return The input manager instance.
     *
     * @hide
     */
    public static InputManager getInstance() {
        synchronized (InputManager.class) {
            if (sInstance == null) {
                IBinder b = ServiceManager.getService(Context.INPUT_SERVICE);
                sInstance = new InputManager(IInputManager.Stub.asInterface(b));
            }
            return sInstance;
        }
    }

    /**
     * Gets information about the input device with the specified id.
     * @param id The device id.
     * @return The input device or null if not found.
     */
    public InputDevice getInputDevice(int id) {
        synchronized (mInputDevicesLock) {
            populateInputDevicesLocked();

            int index = mInputDevices.indexOfKey(id);
            if (index < 0) {
                return null;
            }

            InputDevice inputDevice = mInputDevices.valueAt(index);
            if (inputDevice == null) {
                try {
                    inputDevice = mIm.getInputDevice(id);
                } catch (RemoteException ex) {
                    throw new RuntimeException("Could not get input device information.", ex);
                }
                if (inputDevice != null) {
                    mInputDevices.setValueAt(index, inputDevice);
                }
            }
            return inputDevice;
        }
    }

    /**
     * Gets information about the input device with the specified descriptor.
     * @param descriptor The input device descriptor.
     * @return The input device or null if not found.
     * @hide
     */
    public InputDevice getInputDeviceByDescriptor(String descriptor) {
        if (descriptor == null) {
            throw new IllegalArgumentException("descriptor must not be null.");
        }

        synchronized (mInputDevicesLock) {
            populateInputDevicesLocked();

            int numDevices = mInputDevices.size();
            for (int i = 0; i < numDevices; i++) {
                InputDevice inputDevice = mInputDevices.valueAt(i);
                if (inputDevice == null) {
                    int id = mInputDevices.keyAt(i);
                    try {
                        inputDevice = mIm.getInputDevice(id);
                    } catch (RemoteException ex) {
                        // Ignore the problem for the purposes of this method.
                    }
                    if (inputDevice == null) {
                        continue;
                    }
                    mInputDevices.setValueAt(i, inputDevice);
                }
                if (descriptor.equals(inputDevice.getDescriptor())) {
                    return inputDevice;
                }
            }
            return null;
        }
    }

    /**
     * Gets the ids of all input devices in the system.
     * @return The input device ids.
     */
    public int[] getInputDeviceIds() {
        synchronized (mInputDevicesLock) {
            populateInputDevicesLocked();

            final int count = mInputDevices.size();
            final int[] ids = new int[count];
            for (int i = 0; i < count; i++) {
                ids[i] = mInputDevices.keyAt(i);
            }
            return ids;
        }
    }

    /**
     * Registers an input device listener to receive notifications about when
     * input devices are added, removed or changed.
     *
     * @param listener The listener to register.
     * @param handler The handler on which the listener should be invoked, or null
     * if the listener should be invoked on the calling thread's looper.
     *
     * @see #unregisterInputDeviceListener
     */
    public void registerInputDeviceListener(InputDeviceListener listener, Handler handler) {
        if (listener == null) {
            throw new IllegalArgumentException("listener must not be null");
        }

        synchronized (mInputDevicesLock) {
            int index = findInputDeviceListenerLocked(listener);
            if (index < 0) {
                mInputDeviceListeners.add(new InputDeviceListenerDelegate(listener, handler));
            }
        }
    }

    /**
     * Unregisters an input device listener.
     *
     * @param listener The listener to unregister.
     *
     * @see #registerInputDeviceListener
     */
    public void unregisterInputDeviceListener(InputDeviceListener listener) {
        if (listener == null) {
            throw new IllegalArgumentException("listener must not be null");
        }

        synchronized (mInputDevicesLock) {
            int index = findInputDeviceListenerLocked(listener);
            if (index >= 0) {
                InputDeviceListenerDelegate d = mInputDeviceListeners.get(index);
                d.removeCallbacksAndMessages(null);
                mInputDeviceListeners.remove(index);
            }
        }
    }

    private int findInputDeviceListenerLocked(InputDeviceListener listener) {
        final int numListeners = mInputDeviceListeners.size();
        for (int i = 0; i < numListeners; i++) {
            if (mInputDeviceListeners.get(i).mListener == listener) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Gets information about all supported keyboard layouts.
     * <p>
     * The input manager consults the built-in keyboard layouts as well
     * as all keyboard layouts advertised by applications using a
     * {@link #ACTION_QUERY_KEYBOARD_LAYOUTS} broadcast receiver.
     * </p>
     *
     * @return A list of all supported keyboard layouts.
     *
     * @hide
     */
    public KeyboardLayout[] getKeyboardLayouts() {
        try {
            return mIm.getKeyboardLayouts();
        } catch (RemoteException ex) {
            Log.w(TAG, "Could not get list of keyboard layout informations.", ex);
            return new KeyboardLayout[0];
        }
    }

    /**
     * Gets the keyboard layout with the specified descriptor.
     *
     * @param keyboardLayoutDescriptor The keyboard layout descriptor, as returned by
     * {@link KeyboardLayout#getDescriptor()}.
     * @return The keyboard layout, or null if it could not be loaded.
     *
     * @hide
     */
    public KeyboardLayout getKeyboardLayout(String keyboardLayoutDescriptor) {
        if (keyboardLayoutDescriptor == null) {
            throw new IllegalArgumentException("keyboardLayoutDescriptor must not be null");
        }

        try {
            return mIm.getKeyboardLayout(keyboardLayoutDescriptor);
        } catch (RemoteException ex) {
            Log.w(TAG, "Could not get keyboard layout information.", ex);
            return null;
        }
    }

    /**
     * Gets the current keyboard layout descriptor for the specified input device.
     *
     * @param inputDeviceDescriptor The input device descriptor.
     * @return The keyboard layout descriptor, or null if no keyboard layout has been set.
     *
     * @hide
     */
    public String getCurrentKeyboardLayoutForInputDevice(String inputDeviceDescriptor) {
        if (inputDeviceDescriptor == null) {
            throw new IllegalArgumentException("inputDeviceDescriptor must not be null");
        }

        try {
            return mIm.getCurrentKeyboardLayoutForInputDevice(inputDeviceDescriptor);
        } catch (RemoteException ex) {
            Log.w(TAG, "Could not get current keyboard layout for input device.", ex);
            return null;
        }
    }

    /**
     * Sets the current keyboard layout descriptor for the specified input device.
     * <p>
     * This method may have the side-effect of causing the input device in question
     * to be reconfigured.
     * </p>
     *
     * @param inputDeviceDescriptor The input device descriptor.
     * @param keyboardLayoutDescriptor The keyboard layout descriptor to use, must not be null.
     *
     * @hide
     */
    public void setCurrentKeyboardLayoutForInputDevice(String inputDeviceDescriptor,
            String keyboardLayoutDescriptor) {
        if (inputDeviceDescriptor == null) {
            throw new IllegalArgumentException("inputDeviceDescriptor must not be null");
        }
        if (keyboardLayoutDescriptor == null) {
            throw new IllegalArgumentException("keyboardLayoutDescriptor must not be null");
        }

        try {
            mIm.setCurrentKeyboardLayoutForInputDevice(inputDeviceDescriptor,
                    keyboardLayoutDescriptor);
        } catch (RemoteException ex) {
            Log.w(TAG, "Could not set current keyboard layout for input device.", ex);
        }
    }

    /**
     * Gets all keyboard layout descriptors that are enabled for the specified input device.
     *
     * @param inputDeviceDescriptor The input device descriptor.
     * @return The keyboard layout descriptors.
     *
     * @hide
     */
    public String[] getKeyboardLayoutsForInputDevice(String inputDeviceDescriptor) {
        if (inputDeviceDescriptor == null) {
            throw new IllegalArgumentException("inputDeviceDescriptor must not be null");
        }

        try {
            return mIm.getKeyboardLayoutsForInputDevice(inputDeviceDescriptor);
        } catch (RemoteException ex) {
            Log.w(TAG, "Could not get keyboard layouts for input device.", ex);
            return ArrayUtils.emptyArray(String.class);
        }
    }

    /**
     * Adds the keyboard layout descriptor for the specified input device.
     * <p>
     * This method may have the side-effect of causing the input device in question
     * to be reconfigured.
     * </p>
     *
     * @param inputDeviceDescriptor The input device descriptor.
     * @param keyboardLayoutDescriptor The descriptor of the keyboard layout to add.
     *
     * @hide
     */
    public void addKeyboardLayoutForInputDevice(String inputDeviceDescriptor,
            String keyboardLayoutDescriptor) {
        if (inputDeviceDescriptor == null) {
            throw new IllegalArgumentException("inputDeviceDescriptor must not be null");
        }
        if (keyboardLayoutDescriptor == null) {
            throw new IllegalArgumentException("keyboardLayoutDescriptor must not be null");
        }

        try {
            mIm.addKeyboardLayoutForInputDevice(inputDeviceDescriptor, keyboardLayoutDescriptor);
        } catch (RemoteException ex) {
            Log.w(TAG, "Could not add keyboard layout for input device.", ex);
        }
    }

    /**
     * Removes the keyboard layout descriptor for the specified input device.
     * <p>
     * This method may have the side-effect of causing the input device in question
     * to be reconfigured.
     * </p>
     *
     * @param inputDeviceDescriptor The input device descriptor.
     * @param keyboardLayoutDescriptor The descriptor of the keyboard layout to remove.
     *
     * @hide
     */
    public void removeKeyboardLayoutForInputDevice(String inputDeviceDescriptor,
            String keyboardLayoutDescriptor) {
        if (inputDeviceDescriptor == null) {
            throw new IllegalArgumentException("inputDeviceDescriptor must not be null");
        }
        if (keyboardLayoutDescriptor == null) {
            throw new IllegalArgumentException("keyboardLayoutDescriptor must not be null");
        }

        try {
            mIm.removeKeyboardLayoutForInputDevice(inputDeviceDescriptor, keyboardLayoutDescriptor);
        } catch (RemoteException ex) {
            Log.w(TAG, "Could not remove keyboard layout for input device.", ex);
        }
    }

    /**
     * Gets the mouse pointer speed.
     * <p>
     * Only returns the permanent mouse pointer speed.  Ignores any temporary pointer
     * speed set by {@link #tryPointerSpeed}.
     * </p>
     *
     * @param context The application context.
     * @return The pointer speed as a value between {@link #MIN_POINTER_SPEED} and
     * {@link #MAX_POINTER_SPEED}, or the default value {@link #DEFAULT_POINTER_SPEED}.
     *
     * @hide
     */
    public int getPointerSpeed(Context context) {
        int speed = DEFAULT_POINTER_SPEED;
        try {
            speed = Settings.System.getInt(context.getContentResolver(),
                    Settings.System.POINTER_SPEED);
        } catch (SettingNotFoundException snfe) {
        }
        return speed;
    }

    /**
     * Sets the mouse pointer speed.
     * <p>
     * Requires {@link android.Manifest.permissions.WRITE_SETTINGS}.
     * </p>
     *
     * @param context The application context.
     * @param speed The pointer speed as a value between {@link #MIN_POINTER_SPEED} and
     * {@link #MAX_POINTER_SPEED}, or the default value {@link #DEFAULT_POINTER_SPEED}.
     *
     * @hide
     */
    public void setPointerSpeed(Context context, int speed) {
        if (speed < MIN_POINTER_SPEED || speed > MAX_POINTER_SPEED) {
            throw new IllegalArgumentException("speed out of range");
        }

        Settings.System.putInt(context.getContentResolver(),
                Settings.System.POINTER_SPEED, speed);
    }

    /**
     * Changes the mouse pointer speed temporarily, but does not save the setting.
     * <p>
     * Requires {@link android.Manifest.permission.SET_POINTER_SPEED}.
     * </p>
     *
     * @param speed The pointer speed as a value between {@link #MIN_POINTER_SPEED} and
     * {@link #MAX_POINTER_SPEED}, or the default value {@link #DEFAULT_POINTER_SPEED}.
     *
     * @hide
     */
    public void tryPointerSpeed(int speed) {
        if (speed < MIN_POINTER_SPEED || speed > MAX_POINTER_SPEED) {
            throw new IllegalArgumentException("speed out of range");
        }

        try {
            mIm.tryPointerSpeed(speed);
        } catch (RemoteException ex) {
            Log.w(TAG, "Could not set temporary pointer speed.", ex);
        }
    }

    /**
     * Queries the framework about whether any physical keys exist on the
     * any keyboard attached to the device that are capable of producing the given
     * array of key codes.
     *
     * @param keyCodes The array of key codes to query.
     * @return A new array of the same size as the key codes array whose elements
     * are set to true if at least one attached keyboard supports the corresponding key code
     * at the same index in the key codes array.
     *
     * @hide
     */
    public boolean[] deviceHasKeys(int[] keyCodes) {
        return deviceHasKeys(-1, keyCodes);
    }

    /**
     * Queries the framework about whether any physical keys exist on the
     * any keyboard attached to the device that are capable of producing the given
     * array of key codes.
     *
     * @param id The id of the device to query.
     * @param keyCodes The array of key codes to query.
     * @return A new array of the same size as the key codes array whose elements are set to true
     * if the given device could produce the corresponding key code at the same index in the key
     * codes array.
     *
     * @hide
     */
    public boolean[] deviceHasKeys(int id, int[] keyCodes) {
        boolean[] ret = new boolean[keyCodes.length];
        try {
            mIm.hasKeys(id, InputDevice.SOURCE_ANY, keyCodes, ret);
        } catch (RemoteException e) {
            // no fallback; just return the empty array
        }
        return ret;
    }


    /**
     * Injects an input event into the event system on behalf of an application.
     * The synchronization mode determines whether the method blocks while waiting for
     * input injection to proceed.
     * <p>
     * Requires {@link android.Manifest.permission.INJECT_EVENTS} to inject into
     * windows that are owned by other applications.
     * </p><p>
     * Make sure you correctly set the event time and input source of the event
     * before calling this method.
     * </p>
     *
     * @param event The event to inject.
     * @param mode The synchronization mode.  One of:
     * {@link #INJECT_INPUT_EVENT_MODE_ASYNC},
     * {@link #INJECT_INPUT_EVENT_MODE_WAIT_FOR_RESULT}, or
     * {@link #INJECT_INPUT_EVENT_MODE_WAIT_FOR_FINISH}.
     * @return True if input event injection succeeded.
     *
     * @hide
     */
    public boolean injectInputEvent(InputEvent event, int mode) {
        if (event == null) {
            throw new IllegalArgumentException("event must not be null");
        }
        if (mode != INJECT_INPUT_EVENT_MODE_ASYNC
                && mode != INJECT_INPUT_EVENT_MODE_WAIT_FOR_FINISH
                && mode != INJECT_INPUT_EVENT_MODE_WAIT_FOR_RESULT) {
            throw new IllegalArgumentException("mode is invalid");
        }

        try {
            return mIm.injectInputEvent(event, mode);
        } catch (RemoteException ex) {
            return false;
        }
    }

    private void populateInputDevicesLocked() {
        if (mInputDevicesChangedListener == null) {
            final InputDevicesChangedListener listener = new InputDevicesChangedListener();
            try {
                mIm.registerInputDevicesChangedListener(listener);
            } catch (RemoteException ex) {
                throw new RuntimeException(
                        "Could not get register input device changed listener", ex);
            }
            mInputDevicesChangedListener = listener;
        }

        if (mInputDevices == null) {
            final int[] ids;
            try {
                ids = mIm.getInputDeviceIds();
            } catch (RemoteException ex) {
                throw new RuntimeException("Could not get input device ids.", ex);
            }

            mInputDevices = new SparseArray<InputDevice>();
            for (int i = 0; i < ids.length; i++) {
                mInputDevices.put(ids[i], null);
            }
        }
    }

    private void onInputDevicesChanged(int[] deviceIdAndGeneration) {
        if (DEBUG) {
            Log.d(TAG, "Received input devices changed.");
        }

        synchronized (mInputDevicesLock) {
            for (int i = mInputDevices.size(); --i > 0; ) {
                final int deviceId = mInputDevices.keyAt(i);
                if (!containsDeviceId(deviceIdAndGeneration, deviceId)) {
                    if (DEBUG) {
                        Log.d(TAG, "Device removed: " + deviceId);
                    }
                    mInputDevices.removeAt(i);
                    sendMessageToInputDeviceListenersLocked(MSG_DEVICE_REMOVED, deviceId);
                }
            }

            for (int i = 0; i < deviceIdAndGeneration.length; i += 2) {
                final int deviceId = deviceIdAndGeneration[i];
                int index = mInputDevices.indexOfKey(deviceId);
                if (index >= 0) {
                    final InputDevice device = mInputDevices.valueAt(index);
                    if (device != null) {
                        final int generation = deviceIdAndGeneration[i + 1];
                        if (device.getGeneration() != generation) {
                            if (DEBUG) {
                                Log.d(TAG, "Device changed: " + deviceId);
                            }
                            mInputDevices.setValueAt(index, null);
                            sendMessageToInputDeviceListenersLocked(MSG_DEVICE_CHANGED, deviceId);
                        }
                    }
                } else {
                    if (DEBUG) {
                        Log.d(TAG, "Device added: " + deviceId);
                    }
                    mInputDevices.put(deviceId, null);
                    sendMessageToInputDeviceListenersLocked(MSG_DEVICE_ADDED, deviceId);
                }
            }
        }
    }

    private void sendMessageToInputDeviceListenersLocked(int what, int deviceId) {
        final int numListeners = mInputDeviceListeners.size();
        for (int i = 0; i < numListeners; i++) {
            InputDeviceListenerDelegate listener = mInputDeviceListeners.get(i);
            listener.sendMessage(listener.obtainMessage(what, deviceId, 0));
        }
    }

    private static boolean containsDeviceId(int[] deviceIdAndGeneration, int deviceId) {
        for (int i = 0; i < deviceIdAndGeneration.length; i += 2) {
            if (deviceIdAndGeneration[i] == deviceId) {
                return true;
            }
        }
        return false;
    }

    /**
     * Gets a vibrator service associated with an input device, assuming it has one.
     * @return The vibrator, never null.
     * @hide
     */
    public Vibrator getInputDeviceVibrator(int deviceId) {
        return new InputDeviceVibrator(deviceId);
    }

    /**
     * Listens for changes in input devices.
     */
    public interface InputDeviceListener {
        /**
         * Called whenever an input device has been added to the system.
         * Use {@link InputManager#getInputDevice} to get more information about the device.
         *
         * @param deviceId The id of the input device that was added.
         */
        void onInputDeviceAdded(int deviceId);

        /**
         * Called whenever an input device has been removed from the system.
         *
         * @param deviceId The id of the input device that was removed.
         */
        void onInputDeviceRemoved(int deviceId);

        /**
         * Called whenever the properties of an input device have changed since they
         * were last queried.  Use {@link InputManager#getInputDevice} to get
         * a fresh {@link InputDevice} object with the new properties.
         *
         * @param deviceId The id of the input device that changed.
         */
        void onInputDeviceChanged(int deviceId);
    }

    private final class InputDevicesChangedListener extends IInputDevicesChangedListener.Stub {
        @Override
        public void onInputDevicesChanged(int[] deviceIdAndGeneration) throws RemoteException {
            InputManager.this.onInputDevicesChanged(deviceIdAndGeneration);
        }
    }

    private static final class InputDeviceListenerDelegate extends Handler {
        public final InputDeviceListener mListener;

        public InputDeviceListenerDelegate(InputDeviceListener listener, Handler handler) {
            super(handler != null ? handler.getLooper() : Looper.myLooper());
            mListener = listener;
        }

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case MSG_DEVICE_ADDED:
                    mListener.onInputDeviceAdded(msg.arg1);
                    break;
                case MSG_DEVICE_REMOVED:
                    mListener.onInputDeviceRemoved(msg.arg1);
                    break;
                case MSG_DEVICE_CHANGED:
                    mListener.onInputDeviceChanged(msg.arg1);
                    break;
            }
        }
    }

    private final class InputDeviceVibrator extends Vibrator {
        private final int mDeviceId;
        private final Binder mToken;

        public InputDeviceVibrator(int deviceId) {
            mDeviceId = deviceId;
            mToken = new Binder();
        }

        @Override
        public boolean hasVibrator() {
            return true;
        }

        @Override
        public void vibrate(long milliseconds) {
            vibrate(new long[] { 0, milliseconds}, -1);
        }

        @Override
        public void vibrate(long[] pattern, int repeat) {
            if (repeat >= pattern.length) {
                throw new ArrayIndexOutOfBoundsException();
            }
            try {
                mIm.vibrate(mDeviceId, pattern, repeat, mToken);
            } catch (RemoteException ex) {
                Log.w(TAG, "Failed to vibrate.", ex);
            }
        }

        /**
         * @hide
         */
        @Override
        public void vibrate(int owningUid, String owningPackage, long milliseconds) {
            vibrate(milliseconds);
        }

        /**
         * @hide
         */
        @Override
        public void vibrate(int owningUid, String owningPackage, long[] pattern, int repeat) {
            vibrate(pattern, repeat);
        }

        @Override
        public void cancel() {
            try {
                mIm.cancelVibrate(mDeviceId, mToken);
            } catch (RemoteException ex) {
                Log.w(TAG, "Failed to cancel vibration.", ex);
            }
        }
    }
}