xref: /packages/apps/Settings/src/com/android/settings/bluetooth/CachedBluetoothDevice.java

/*
 * Copyright (C) 2008 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 com.android.settings.bluetooth;

import android.app.AlertDialog;
import android.bluetooth.BluetoothClass;
import android.bluetooth.BluetoothDevice;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.res.Resources;
import android.text.TextUtils;
import android.util.Log;
import android.view.ContextMenu;
import android.view.Menu;
import android.view.MenuItem;

import com.android.settings.R;
import com.android.settings.bluetooth.LocalBluetoothProfileManager.Profile;

import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

/**
 * LocalBluetoothDevice represents a remote Bluetooth device. It contains
 * attributes of the device (such as the address, name, RSSI, etc.) and
 * functionality that can be performed on the device (connect, pair, disconnect,
 * etc.).
 */
public class LocalBluetoothDevice implements Comparable<LocalBluetoothDevice> {
    private static final String TAG = "LocalBluetoothDevice";
    private static final boolean D = LocalBluetoothManager.D;
    private static final boolean V = LocalBluetoothManager.V;

    private static final int CONTEXT_ITEM_CONNECT = Menu.FIRST + 1;
    private static final int CONTEXT_ITEM_DISCONNECT = Menu.FIRST + 2;
    private static final int CONTEXT_ITEM_UNPAIR = Menu.FIRST + 3;
    private static final int CONTEXT_ITEM_CONNECT_ADVANCED = Menu.FIRST + 4;

    private final String mAddress;
    private String mName;
    private short mRssi;
    private int mBtClass = BluetoothClass.ERROR;

    private List<Profile> mProfiles = new ArrayList<Profile>();

    private boolean mVisible;

    private final LocalBluetoothManager mLocalManager;

    private List<Callback> mCallbacks = new ArrayList<Callback>();

    /**
     * When we connect to multiple profiles, we only want to display a single
     * error even if they all fail. This tracks that state.
     */
    private boolean mIsConnectingErrorPossible;

    // Max time to hold the work queue if we don't get or missed a response
    // from the bt framework.
    private static final long MAX_WAIT_TIME_FOR_FRAMEWORK = 25 * 1000;

    private enum BluetoothCommand {
        CONNECT, DISCONNECT,
    }

    class BluetoothJob {
        final BluetoothCommand command; // CONNECT, DISCONNECT
        final LocalBluetoothDevice device;
        final Profile profile; // HEADSET, A2DP, etc
        // 0 means this command was not been sent to the bt framework.
        long timeSent;

        public BluetoothJob(BluetoothCommand command,
                LocalBluetoothDevice device, Profile profile) {
            this.command = command;
            this.device = device;
            this.profile = profile;
            this.timeSent = 0;
        }

        @Override
        public String toString() {
            StringBuilder sb = new StringBuilder();
            sb.append(command.name());
            sb.append(" Address:").append(device.mAddress);
            sb.append(" Profile:").append(profile.name());
            sb.append(" TimeSent:");
            if (timeSent == 0) {
                sb.append("not yet");
            } else {
                sb.append(DateFormat.getTimeInstance().format(new Date(timeSent)));
            }
            return sb.toString();
        }
    }

    /**
     * We want to serialize connect and disconnect calls. http://b/170538
     * This are some headsets that may have L2CAP resource limitation. We want
     * to limit the bt bandwidth usage.
     *
     * A queue to keep track of asynchronous calls to the bt framework.  The
     * first item, if exist, should be in progress i.e. went to the bt framework
     * already, waiting for a notification to come back. The second item and
     * beyond have not been sent to the bt framework yet.
     */
    private static LinkedList<BluetoothJob> workQueue = new LinkedList<BluetoothJob>();

    private void queueCommand(BluetoothJob job) {
        if (D) {
            Log.d(TAG, workQueue.toString());
        }
        synchronized (workQueue) {
            boolean processNow = pruneQueue(job);

            // Add job to queue
            if (D) {
                Log.d(TAG, "Adding: " + job.toString());
            }
            workQueue.add(job);

            // if there's nothing pending from before, send the command to bt
            // framework immediately.
            if (workQueue.size() == 1 || processNow) {
                // If the failed to process, just drop it from the queue.
                // There will be no callback to remove this from the queue.
                processCommands();
            }
        }
    }

    private boolean pruneQueue(BluetoothJob job) {
        boolean removedStaleItems = false;
        long now = System.currentTimeMillis();
        Iterator<BluetoothJob> it = workQueue.iterator();
        while (it.hasNext()) {
            BluetoothJob existingJob = it.next();

            // Remove any pending CONNECTS when we receive a DISCONNECT
            if (job != null && job.command == BluetoothCommand.DISCONNECT) {
                if (existingJob.timeSent == 0
                        && existingJob.command == BluetoothCommand.CONNECT
                        && existingJob.device.mAddress.equals(job.device.mAddress)
                        && existingJob.profile == job.profile) {
                    if (D) {
                        Log.d(TAG, "Removed because of a pending disconnect. " + existingJob);
                    }
                    it.remove();
                    continue;
                }
            }

            // Defensive Code: Remove any job that older than a preset time.
            // We never got a call back. It is better to have overlapping
            // calls than to get stuck.
            if (existingJob.timeSent != 0
                    && (now - existingJob.timeSent) >= MAX_WAIT_TIME_FOR_FRAMEWORK) {
                Log.w(TAG, "Timeout. Removing Job:" + existingJob.toString());
                it.remove();
                removedStaleItems = true;
                continue;
            }
        }
        return removedStaleItems;
    }

    private boolean processCommand(BluetoothJob job) {
        boolean successful = false;
        if (job.timeSent == 0) {
            job.timeSent = System.currentTimeMillis();
            switch (job.command) {
            case CONNECT:
                successful = connectInt(job.device, job.profile);
                break;
            case DISCONNECT:
                successful = disconnectInt(job.device, job.profile);
                break;
            }

            if (successful) {
                if (D) {
                    Log.d(TAG, "Command sent successfully:" + job.toString());
                }
            } else if (V) {
                Log.v(TAG, "Framework rejected command immediately:" + job.toString());
            }
        } else if (D) {
            Log.d(TAG, "Job already has a sent time. Skip. " + job.toString());
        }

        return successful;
    }

    public void onProfileStateChanged(Profile profile, int newProfileState) {
        if (D) {
            Log.d(TAG, "onProfileStateChanged:" + workQueue.toString());
        }

        int newState = LocalBluetoothProfileManager.getProfileManager(mLocalManager,
                profile).convertState(newProfileState);

        if (newState == SettingsBtStatus.CONNECTION_STATUS_CONNECTED) {
            if (!mProfiles.contains(profile)) {
                mProfiles.add(profile);
            }
        }

        /* Ignore the transient states e.g. connecting, disconnecting */
        if (newState == SettingsBtStatus.CONNECTION_STATUS_CONNECTED ||
                newState == SettingsBtStatus.CONNECTION_STATUS_DISCONNECTED) {
            BluetoothJob job = workQueue.peek();
            if (job == null) {
                return;
            } else if (job.device.mAddress != mAddress) {
                // This can happen in 2 cases: 1) BT device initiated pairing and
                // 2) disconnects of one headset that's triggered by connects of
                // another.
                if (D) {
                    Log.d(TAG, "mAddresses:" + mAddress + " != head:" + job.toString());
                }

                // Check to see if we need to remove the stale items from the queue
                if (!pruneQueue(null)) {
                    // nothing in the queue was modify. Just ignore the notification and return.
                    return;
                }
            } else {
                // Remove the first item and process the next one
                workQueue.poll();
            }

            processCommands();
        }
    }

    /*
     * This method is called in 2 places:
     * 1) queryCommand() - when someone or something want to connect or
     *    disconnect
     * 2) onProfileStateChanged() - when the framework sends an intent
     *    notification when it finishes processing a command
     */
    private void processCommands() {
        if (D) {
            Log.d(TAG, "processCommands:" + workQueue.toString());
        }
        Iterator<BluetoothJob> it = workQueue.iterator();
        while (it.hasNext()) {
            BluetoothJob job = it.next();
            if (processCommand(job)) {
                // Sent to bt framework. Done for now. Will remove this job
                // from queue when we get an event
                return;
            } else {
                /*
                 * If the command failed immediately, there will be no event
                 * callbacks. So delete the job immediately and move on to the
                 * next one
                 */
                it.remove();
            }
        }
    }

    LocalBluetoothDevice(Context context, String address) {
        mLocalManager = LocalBluetoothManager.getInstance(context);
        if (mLocalManager == null) {
            throw new IllegalStateException(
                    "Cannot use LocalBluetoothDevice without Bluetooth hardware");
        }

        mAddress = address;

        fillData();
    }

    public void onClicked() {
        int bondState = getBondState();

        if (isConnected()) {
            askDisconnect();
        } else if (bondState == BluetoothDevice.BOND_BONDED) {
            connect();
        } else if (bondState == BluetoothDevice.BOND_NOT_BONDED) {
            pair();
        }
    }

    public void disconnect() {
        for (Profile profile : mProfiles) {
            disconnect(profile);
        }
    }

    public void disconnect(Profile profile) {
        queueCommand(new BluetoothJob(BluetoothCommand.DISCONNECT, this, profile));
    }

    private boolean disconnectInt(LocalBluetoothDevice device, Profile profile) {
        LocalBluetoothProfileManager profileManager =
                LocalBluetoothProfileManager.getProfileManager(mLocalManager, profile);
        int status = profileManager.getConnectionStatus(device.mAddress);
        if (SettingsBtStatus.isConnectionStatusConnected(status)) {
            if (profileManager.disconnect(device.mAddress) == BluetoothDevice.RESULT_SUCCESS) {
                return true;
            }
        }
        return false;
    }

    public void askDisconnect() {
        Context context = mLocalManager.getForegroundActivity();
        if (context == null) {
            // Cannot ask, since we need an activity context
            disconnect();
            return;
        }

        Resources res = context.getResources();

        String name = getName();
        if (TextUtils.isEmpty(name)) {
            name = res.getString(R.string.bluetooth_device);
        }
        String message = res.getString(R.string.bluetooth_disconnect_blank, name);

        DialogInterface.OnClickListener disconnectListener = new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                disconnect();
            }
        };

        AlertDialog ad = new AlertDialog.Builder(context)
                .setTitle(getName())
                .setMessage(message)
                .setPositiveButton(android.R.string.ok, disconnectListener)
                .setNegativeButton(android.R.string.cancel, null)
                .show();
    }

    public void connect() {
        if (!ensurePaired()) return;

        // Reset the only-show-one-error-dialog tracking variable
        mIsConnectingErrorPossible = true;

        Context context = mLocalManager.getContext();
        boolean hasAtLeastOnePreferredProfile = false;
        for (Profile profile : mProfiles) {
            LocalBluetoothProfileManager profileManager =
                    LocalBluetoothProfileManager.getProfileManager(mLocalManager, profile);
            if (profileManager.isPreferred(mAddress)) {
                hasAtLeastOnePreferredProfile = true;
                queueCommand(new BluetoothJob(BluetoothCommand.CONNECT, this, profile));
            }
        }

        if (!hasAtLeastOnePreferredProfile) {
            connectAndPreferAllProfiles();
        }
    }

    private void connectAndPreferAllProfiles() {
        if (!ensurePaired()) return;

        // Reset the only-show-one-error-dialog tracking variable
        mIsConnectingErrorPossible = true;

        Context context = mLocalManager.getContext();
        for (Profile profile : mProfiles) {
            LocalBluetoothProfileManager profileManager =
                    LocalBluetoothProfileManager.getProfileManager(mLocalManager, profile);
            profileManager.setPreferred(mAddress, true);
            queueCommand(new BluetoothJob(BluetoothCommand.CONNECT, this, profile));
        }
    }

    public void connect(Profile profile) {
        // Reset the only-show-one-error-dialog tracking variable
        mIsConnectingErrorPossible = true;
        queueCommand(new BluetoothJob(BluetoothCommand.CONNECT, this, profile));
    }

    private boolean connectInt(LocalBluetoothDevice device, Profile profile) {
        if (!device.ensurePaired()) return false;

        LocalBluetoothProfileManager profileManager =
                LocalBluetoothProfileManager.getProfileManager(mLocalManager, profile);
        int status = profileManager.getConnectionStatus(device.mAddress);
        if (!SettingsBtStatus.isConnectionStatusConnected(status)) {
            if (profileManager.connect(device.mAddress) == BluetoothDevice.RESULT_SUCCESS) {
                return true;
            }
            Log.i(TAG, "Failed to connect " + profile.toString() + " to " + device.mName);
        }
        Log.i(TAG, "Not connected");
        return false;
    }

    public void showConnectingError() {
        if (!mIsConnectingErrorPossible) return;
        mIsConnectingErrorPossible = false;

        mLocalManager.showError(mAddress, R.string.bluetooth_error_title,
                R.string.bluetooth_connecting_error_message);
    }

    private boolean ensurePaired() {
        if (getBondState() == BluetoothDevice.BOND_NOT_BONDED) {
            pair();
            return false;
        } else {
            return true;
        }
    }

    public void pair() {
        BluetoothDevice manager = mLocalManager.getBluetoothManager();

        // Pairing is unreliable while scanning, so cancel discovery
        if (manager.isDiscovering()) {
            manager.cancelDiscovery();
        }

        if (!mLocalManager.getBluetoothManager().createBond(mAddress)) {
            mLocalManager.showError(mAddress, R.string.bluetooth_error_title,
                    R.string.bluetooth_pairing_error_message);
        }
    }

    public void unpair() {
        synchronized (workQueue) {
            // Remove any pending commands for this device
            boolean processNow = false;
            Iterator<BluetoothJob> it = workQueue.iterator();
            while (it.hasNext()) {
                BluetoothJob job = it.next();
                if (job.device.mAddress.equals(this.mAddress)) {
                    it.remove();
                    if (job.timeSent != 0) {
                        processNow = true;
                    }
                }
            }
            if (processNow) {
                processCommands();
            }
        }

        BluetoothDevice manager = mLocalManager.getBluetoothManager();

        switch (getBondState()) {
        case BluetoothDevice.BOND_BONDED:
            manager.removeBond(mAddress);
            break;

        case BluetoothDevice.BOND_BONDING:
            manager.cancelBondProcess(mAddress);
            break;
        }
    }

    private void fillData() {
        BluetoothDevice manager = mLocalManager.getBluetoothManager();

        fetchName();
        fetchBtClass();

        mVisible = false;

        dispatchAttributesChanged();
    }

    public String getAddress() {
        return mAddress;
    }

    public String getName() {
        return mName;
    }

    public void refreshName() {
        fetchName();
        dispatchAttributesChanged();
    }

    private void fetchName() {
        mName = mLocalManager.getBluetoothManager().getRemoteName(mAddress);

        if (TextUtils.isEmpty(mName)) {
            mName = mAddress;
        }
    }

    public void refresh() {
        dispatchAttributesChanged();
    }

    public boolean isVisible() {
        return mVisible;
    }

    void setVisible(boolean visible) {
        if (mVisible != visible) {
            mVisible = visible;
            dispatchAttributesChanged();
        }
    }

    public int getBondState() {
        return mLocalManager.getBluetoothManager().getBondState(mAddress);
    }

    void setRssi(short rssi) {
        if (mRssi != rssi) {
            mRssi = rssi;
            dispatchAttributesChanged();
        }
    }

    /**
     * Checks whether we are connected to this device (any profile counts).
     *
     * @return Whether it is connected.
     */
    public boolean isConnected() {
        for (Profile profile : mProfiles) {
            int status = LocalBluetoothProfileManager.getProfileManager(mLocalManager, profile)
                    .getConnectionStatus(mAddress);
            if (SettingsBtStatus.isConnectionStatusConnected(status)) {
                return true;
            }
        }

        return false;
    }

    public boolean isBusy() {
        for (Profile profile : mProfiles) {
            int status = LocalBluetoothProfileManager.getProfileManager(mLocalManager, profile)
                    .getConnectionStatus(mAddress);
            if (SettingsBtStatus.isConnectionStatusBusy(status)) {
                return true;
            }
        }

        if (getBondState() == BluetoothDevice.BOND_BONDING) {
            return true;
        }

        return false;
    }

    public int getBtClassDrawable() {

        // First try looking at profiles
        if (mProfiles.contains(Profile.A2DP)) {
            return R.drawable.ic_bt_headphones_a2dp;
        } else if (mProfiles.contains(Profile.HEADSET)) {
            return R.drawable.ic_bt_headset_hfp;
        }

        // Fallback on class
        switch (BluetoothClass.Device.Major.getDeviceMajor(mBtClass)) {
        case BluetoothClass.Device.Major.COMPUTER:
            return R.drawable.ic_bt_laptop;

        case BluetoothClass.Device.Major.PHONE:
            return R.drawable.ic_bt_cellphone;

        default:
            return 0;
        }
    }

    /**
     * Fetches a new value for the cached BT class.
     */
    private void fetchBtClass() {
        mBtClass = mLocalManager.getBluetoothManager().getRemoteClass(mAddress);
        if (mBtClass != BluetoothClass.ERROR) {
            LocalBluetoothProfileManager.fill(mBtClass, mProfiles);
        }
    }

    /**
     * Refreshes the UI for the BT class, including fetching the latest value
     * for the class.
     */
    public void refreshBtClass() {
        fetchBtClass();
        dispatchAttributesChanged();
    }

    public int getSummary() {
        // TODO: clean up
        int oneOffSummary = getOneOffSummary();
        if (oneOffSummary != 0) {
            return oneOffSummary;
        }

        for (Profile profile : mProfiles) {
            LocalBluetoothProfileManager profileManager = LocalBluetoothProfileManager
                    .getProfileManager(mLocalManager, profile);
            int connectionStatus = profileManager.getConnectionStatus(mAddress);

            if (SettingsBtStatus.isConnectionStatusConnected(connectionStatus) ||
                    connectionStatus == SettingsBtStatus.CONNECTION_STATUS_CONNECTING ||
                    connectionStatus == SettingsBtStatus.CONNECTION_STATUS_DISCONNECTING) {
                return SettingsBtStatus.getConnectionStatusSummary(connectionStatus);
            }
        }

        return SettingsBtStatus.getPairingStatusSummary(getBondState());
    }

    /**
     * We have special summaries when particular profiles are connected. This
     * checks for those states and returns an applicable summary.
     *
     * @return A one-off summary that is applicable for the current state, or 0.
     */
    private int getOneOffSummary() {
        boolean isA2dpConnected = false, isHeadsetConnected = false, isConnecting = false;

        if (mProfiles.contains(Profile.A2DP)) {
            LocalBluetoothProfileManager profileManager = LocalBluetoothProfileManager
                    .getProfileManager(mLocalManager, Profile.A2DP);
            isConnecting = profileManager.getConnectionStatus(mAddress) ==
                    SettingsBtStatus.CONNECTION_STATUS_CONNECTING;
            isA2dpConnected = profileManager.isConnected(mAddress);
        }

        if (mProfiles.contains(Profile.HEADSET)) {
            LocalBluetoothProfileManager profileManager = LocalBluetoothProfileManager
                    .getProfileManager(mLocalManager, Profile.HEADSET);
            isConnecting |= profileManager.getConnectionStatus(mAddress) ==
                    SettingsBtStatus.CONNECTION_STATUS_CONNECTING;
            isHeadsetConnected = profileManager.isConnected(mAddress);
        }

        if (isConnecting) {
            // If any of these important profiles is connecting, prefer that
            return SettingsBtStatus.getConnectionStatusSummary(
                    SettingsBtStatus.CONNECTION_STATUS_CONNECTING);
        } else if (isA2dpConnected && isHeadsetConnected) {
            return R.string.bluetooth_summary_connected_to_a2dp_headset;
        } else if (isA2dpConnected) {
            return R.string.bluetooth_summary_connected_to_a2dp;
        } else if (isHeadsetConnected) {
            return R.string.bluetooth_summary_connected_to_headset;
        } else {
            return 0;
        }
    }

    public List<Profile> getProfiles() {
        return new ArrayList<Profile>(mProfiles);
    }

    public void onCreateContextMenu(ContextMenu menu) {
        // No context menu if it is busy (none of these items are applicable if busy)
        if (isBusy()) return;

        int bondState = getBondState();
        boolean isConnected = isConnected();
        boolean hasProfiles = mProfiles.size() > 0;

        menu.setHeaderTitle(getName());

        if (isConnected) {
            menu.add(0, CONTEXT_ITEM_DISCONNECT, 0, R.string.bluetooth_device_context_disconnect);
        } else if (hasProfiles) {
            // For connection action, show either "Connect" or "Pair & connect"
            int connectString = (bondState == BluetoothDevice.BOND_NOT_BONDED)
                    ? R.string.bluetooth_device_context_pair_connect
                    : R.string.bluetooth_device_context_connect;
            menu.add(0, CONTEXT_ITEM_CONNECT, 0, connectString);
        }

        if (bondState == BluetoothDevice.BOND_BONDED) {
            // For unpair action, show either "Unpair" or "Disconnect & unpair"
            int unpairString = isConnected
                    ? R.string.bluetooth_device_context_disconnect_unpair
                    : R.string.bluetooth_device_context_unpair;
            menu.add(0, CONTEXT_ITEM_UNPAIR, 0, unpairString);

            // Show the connection options item
            menu.add(0, CONTEXT_ITEM_CONNECT_ADVANCED, 0,
                    R.string.bluetooth_device_context_connect_advanced);
        }
    }

    /**
     * Called when a context menu item is clicked.
     *
     * @param item The item that was clicked.
     */
    public void onContextItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case CONTEXT_ITEM_DISCONNECT:
                disconnect();
                break;

            case CONTEXT_ITEM_CONNECT:
                connect();
                break;

            case CONTEXT_ITEM_UNPAIR:
                mLocalManager.getBluetoothManager().disconnectRemoteDeviceAcl(mAddress);
                unpair();
                break;

            case CONTEXT_ITEM_CONNECT_ADVANCED:
                Intent intent = new Intent();
                // Need an activity context to open this in our task
                Context context = mLocalManager.getForegroundActivity();
                if (context == null) {
                    // Fallback on application context, and open in a new task
                    context = mLocalManager.getContext();
                    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                }
                intent.setClass(context, ConnectSpecificProfilesActivity.class);
                intent.putExtra(ConnectSpecificProfilesActivity.EXTRA_ADDRESS, mAddress);
                context.startActivity(intent);
                break;
        }
    }

    public void registerCallback(Callback callback) {
        synchronized (mCallbacks) {
            mCallbacks.add(callback);
        }
    }

    public void unregisterCallback(Callback callback) {
        synchronized (mCallbacks) {
            mCallbacks.remove(callback);
        }
    }

    private void dispatchAttributesChanged() {
        synchronized (mCallbacks) {
            for (Callback callback : mCallbacks) {
                callback.onDeviceAttributesChanged(this);
            }
        }
    }

    @Override
    public String toString() {
        return mAddress;
    }

    @Override
    public boolean equals(Object o) {
        if ((o == null) || !(o instanceof LocalBluetoothDevice)) {
            throw new ClassCastException();
        }

        return mAddress.equals(((LocalBluetoothDevice) o).mAddress);
    }

    @Override
    public int hashCode() {
        return mAddress.hashCode();
    }

    public int compareTo(LocalBluetoothDevice another) {
        int comparison;

        // Connected above not connected
        comparison = (another.isConnected() ? 1 : 0) - (isConnected() ? 1 : 0);
        if (comparison != 0) return comparison;

        // Paired above not paired
        comparison = (another.getBondState() == BluetoothDevice.BOND_BONDED ? 1 : 0) -
            (getBondState() == BluetoothDevice.BOND_BONDED ? 1 : 0);
        if (comparison != 0) return comparison;

        // Visible above not visible
        comparison = (another.mVisible ? 1 : 0) - (mVisible ? 1 : 0);
        if (comparison != 0) return comparison;

        // Stronger signal above weaker signal
        comparison = another.mRssi - mRssi;
        if (comparison != 0) return comparison;

        // Fallback on name
        return getName().compareTo(another.getName());
    }

    public interface Callback {
        void onDeviceAttributesChanged(LocalBluetoothDevice device);
    }
}