https://source.android.com/ 
/*
 * Copyright (C) 2014 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.bluetooth.le;

import android.Manifest;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.annotation.RequiresPermission;
import android.annotation.SystemApi;
import android.app.ActivityThread;
import android.app.PendingIntent;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothGatt;
import android.bluetooth.IBluetoothGatt;
import android.bluetooth.IBluetoothManager;
import android.os.Handler;
import android.os.Looper;
import android.os.RemoteException;
import android.os.WorkSource;
import android.util.Log;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


This class provides methods to perform scan related operations for Bluetooth LE devices. An application can scan for a particular type of Bluetooth LE devices using ScanFilter. It can also request different types of callbacks for delivering the result. 
 Use BluetoothAdapter.getBluetoothLeScanner() to get an instance of BluetoothLeScanner. 

Note: Most of the scan methods here require BLUETOOTH_ADMIN.BLUETOOTH_ADMIN permission. 
See Also:
/**
 * This class provides methods to perform scan related operations for Bluetooth LE devices. An
 * application can scan for a particular type of Bluetooth LE devices using {@link ScanFilter}. It
 * can also request different types of callbacks for delivering the result.
 * <p>
 * Use {@link BluetoothAdapter#getBluetoothLeScanner()} to get an instance of
 * {@link BluetoothLeScanner}.
 * <p>
 * <b>Note:</b> Most of the scan methods here require
 * {@link android.Manifest.permission#BLUETOOTH_ADMIN} permission.
 *
 * @see ScanFilter
 */
public final class BluetoothLeScanner {

    private static final String TAG = "BluetoothLeScanner";
    private static final boolean DBG = true;
    private static final boolean VDBG = false;

    
Extra containing a list of ScanResults. It can have one or more results if there was no error. In case of error, EXTRA_ERROR_CODE will contain the error code and this extra will not be available. 
/**
     * Extra containing a list of ScanResults. It can have one or more results if there was no
     * error. In case of error, {@link #EXTRA_ERROR_CODE} will contain the error code and this
     * extra will not be available.
     */
    public static final String EXTRA_LIST_SCAN_RESULT =
            "android.bluetooth.le.extra.LIST_SCAN_RESULT";

    
Optional extra indicating the error code, if any. The error code will be one of the SCAN_FAILED_* codes in ScanCallback. 
/**
     * Optional extra indicating the error code, if any. The error code will be one of the
     * SCAN_FAILED_* codes in {@link ScanCallback}.
     */
    public static final String EXTRA_ERROR_CODE = "android.bluetooth.le.extra.ERROR_CODE";

    
Optional extra indicating the callback type, which will be one of CALLBACK_TYPE_* constants in ScanSettings. 
See Also:
/**
     * Optional extra indicating the callback type, which will be one of
     * CALLBACK_TYPE_* constants in {@link ScanSettings}.
     *
     * @see ScanCallback#onScanResult(int, ScanResult)
     */
    public static final String EXTRA_CALLBACK_TYPE = "android.bluetooth.le.extra.CALLBACK_TYPE";

    private final IBluetoothManager mBluetoothManager;
    private final Handler mHandler;
    private BluetoothAdapter mBluetoothAdapter;
    private final Map<ScanCallback, BleScanCallbackWrapper> mLeScanClients;

    
Params:
  • bluetoothManager – BluetoothManager that conducts overall Bluetooth Management.
@hide
/**
     * Use {@link BluetoothAdapter#getBluetoothLeScanner()} instead.
     *
     * @param bluetoothManager BluetoothManager that conducts overall Bluetooth Management.
     * @hide
     */
    public BluetoothLeScanner(IBluetoothManager bluetoothManager) {
        mBluetoothManager = bluetoothManager;
        mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        mHandler = new Handler(Looper.getMainLooper());
        mLeScanClients = new HashMap<ScanCallback, BleScanCallbackWrapper>();
    }

    
Start Bluetooth LE scan with default parameters and no filters. The scan results will be delivered through callback. For unfiltered scans, scanning is stopped on screen off to save power. Scanning is resumed when screen is turned on again. To avoid this, use startScan(List<ScanFilter>, ScanSettings, ScanCallback) with desired ScanFilter. 
 An app must hold ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION permission in order to get results. 
Params:
  • callback – Callback used to deliver scan results.
Throws:
/**
     * Start Bluetooth LE scan with default parameters and no filters. The scan results will be
     * delivered through {@code callback}. For unfiltered scans, scanning is stopped on screen
     * off to save power. Scanning is resumed when screen is turned on again. To avoid this, use
     * {@link #startScan(List, ScanSettings, ScanCallback)} with desired {@link ScanFilter}.
     * <p>
     * An app must hold
     * {@link android.Manifest.permission#ACCESS_COARSE_LOCATION ACCESS_COARSE_LOCATION} or
     * {@link android.Manifest.permission#ACCESS_FINE_LOCATION ACCESS_FINE_LOCATION} permission
     * in order to get results.
     *
     * @param callback Callback used to deliver scan results.
     * @throws IllegalArgumentException If {@code callback} is null.
     */
    @RequiresPermission(Manifest.permission.BLUETOOTH_ADMIN)
    public void startScan(final ScanCallback callback) {
        startScan(null, new ScanSettings.Builder().build(), callback);
    }

    
Start Bluetooth LE scan. The scan results will be delivered through callback. For unfiltered scans, scanning is stopped on screen off to save power. Scanning is resumed when screen is turned on again. To avoid this, do filetered scanning by using proper ScanFilter. 
 An app must hold ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION permission in order to get results. 
Params:
  • filters – ScanFilters for finding exact BLE devices.
  • settings – Settings for the scan.
  • callback – Callback used to deliver scan results.
Throws:
/**
     * Start Bluetooth LE scan. The scan results will be delivered through {@code callback}.
     * For unfiltered scans, scanning is stopped on screen off to save power. Scanning is
     * resumed when screen is turned on again. To avoid this, do filetered scanning by
     * using proper {@link ScanFilter}.
     * <p>
     * An app must hold
     * {@link android.Manifest.permission#ACCESS_COARSE_LOCATION ACCESS_COARSE_LOCATION} or
     * {@link android.Manifest.permission#ACCESS_FINE_LOCATION ACCESS_FINE_LOCATION} permission
     * in order to get results.
     *
     * @param filters {@link ScanFilter}s for finding exact BLE devices.
     * @param settings Settings for the scan.
     * @param callback Callback used to deliver scan results.
     * @throws IllegalArgumentException If {@code settings} or {@code callback} is null.
     */
    @RequiresPermission(Manifest.permission.BLUETOOTH_ADMIN)
    public void startScan(List<ScanFilter> filters, ScanSettings settings,
            final ScanCallback callback) {
        startScan(filters, settings, null, callback, /*callbackIntent=*/ null, null);
    }

    
Start Bluetooth LE scan using a PendingIntent. The scan results will be delivered via the PendingIntent. Use this method of scanning if your process is not always running and it should be started when scan results are available. 
 An app must hold ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION permission in order to get results. 
 When the PendingIntent is delivered, the Intent passed to the receiver or activity will contain one or more of the extras EXTRA_CALLBACK_TYPE, EXTRA_ERROR_CODE and EXTRA_LIST_SCAN_RESULT to indicate the result of the scan. 
Params:
  • filters – Optional list of ScanFilters for finding exact BLE devices.
  • settings – Optional settings for the scan.
  • callbackIntent – The PendingIntent to deliver the result to.
See Also:
Returns:Returns 0 for success or an error code from ScanCallback if the scan request could not be sent.
/**
     * Start Bluetooth LE scan using a {@link PendingIntent}. The scan results will be delivered via
     * the PendingIntent. Use this method of scanning if your process is not always running and it
     * should be started when scan results are available.
     * <p>
     * An app must hold
     * {@link android.Manifest.permission#ACCESS_COARSE_LOCATION ACCESS_COARSE_LOCATION} or
     * {@link android.Manifest.permission#ACCESS_FINE_LOCATION ACCESS_FINE_LOCATION} permission
     * in order to get results.
     * <p>
     * When the PendingIntent is delivered, the Intent passed to the receiver or activity
     * will contain one or more of the extras {@link #EXTRA_CALLBACK_TYPE},
     * {@link #EXTRA_ERROR_CODE} and {@link #EXTRA_LIST_SCAN_RESULT} to indicate the result of
     * the scan.
     *
     * @param filters Optional list of ScanFilters for finding exact BLE devices.
     * @param settings Optional settings for the scan.
     * @param callbackIntent The PendingIntent to deliver the result to.
     * @return Returns 0 for success or an error code from {@link ScanCallback} if the scan request
     * could not be sent.
     * @see #stopScan(PendingIntent)
     */
    @RequiresPermission(Manifest.permission.BLUETOOTH_ADMIN)
    public int startScan(@Nullable List<ScanFilter> filters, @Nullable ScanSettings settings,
            @NonNull PendingIntent callbackIntent) {
        return startScan(filters,
                settings != null ? settings : new ScanSettings.Builder().build(),
                null, null, callbackIntent, null);
    }

    
Start Bluetooth LE scan. Same as startScan(ScanCallback) but allows the caller to specify on behalf of which application(s) the work is being done. 
Params:
  • workSource – WorkSource identifying the application(s) for which to blame for the scan.
  • callback – Callback used to deliver scan results.
@hide
/**
     * Start Bluetooth LE scan. Same as {@link #startScan(ScanCallback)} but allows the caller to
     * specify on behalf of which application(s) the work is being done.
     *
     * @param workSource {@link WorkSource} identifying the application(s) for which to blame for
     * the scan.
     * @param callback Callback used to deliver scan results.
     * @hide
     */
    @SystemApi
    @RequiresPermission(allOf = {
            Manifest.permission.BLUETOOTH_ADMIN, Manifest.permission.UPDATE_DEVICE_STATS})
    public void startScanFromSource(final WorkSource workSource, final ScanCallback callback) {
        startScanFromSource(null, new ScanSettings.Builder().build(), workSource, callback);
    }

    
Start Bluetooth LE scan. Same as startScan(List<ScanFilter>, ScanSettings, ScanCallback) but allows the caller to specify on behalf of which application(s) the work is being done. 
Params:
  • filters – ScanFilters for finding exact BLE devices.
  • settings – Settings for the scan.
  • workSource – WorkSource identifying the application(s) for which to blame for the scan.
  • callback – Callback used to deliver scan results.
@hide
/**
     * Start Bluetooth LE scan. Same as {@link #startScan(List, ScanSettings, ScanCallback)} but
     * allows the caller to specify on behalf of which application(s) the work is being done.
     *
     * @param filters {@link ScanFilter}s for finding exact BLE devices.
     * @param settings Settings for the scan.
     * @param workSource {@link WorkSource} identifying the application(s) for which to blame for
     * the scan.
     * @param callback Callback used to deliver scan results.
     * @hide
     */
    @SystemApi
    @RequiresPermission(allOf = {
            Manifest.permission.BLUETOOTH_ADMIN, Manifest.permission.UPDATE_DEVICE_STATS})
    public void startScanFromSource(List<ScanFilter> filters, ScanSettings settings,
            final WorkSource workSource, final ScanCallback callback) {
        startScan(filters, settings, workSource, callback, null, null);
    }

    private int startScan(List<ScanFilter> filters, ScanSettings settings,
            final WorkSource workSource, final ScanCallback callback,
            final PendingIntent callbackIntent,
            List<List<ResultStorageDescriptor>> resultStorages) {
        BluetoothLeUtils.checkAdapterStateOn(mBluetoothAdapter);
        if (callback == null && callbackIntent == null) {
            throw new IllegalArgumentException("callback is null");
        }
        if (settings == null) {
            throw new IllegalArgumentException("settings is null");
        }
        synchronized (mLeScanClients) {
            if (callback != null && mLeScanClients.containsKey(callback)) {
                return postCallbackErrorOrReturn(callback,
                            ScanCallback.SCAN_FAILED_ALREADY_STARTED);
            }
            IBluetoothGatt gatt;
            try {
                gatt = mBluetoothManager.getBluetoothGatt();
            } catch (RemoteException e) {
                gatt = null;
            }
            if (gatt == null) {
                return postCallbackErrorOrReturn(callback, ScanCallback.SCAN_FAILED_INTERNAL_ERROR);
            }
            if (!isSettingsConfigAllowedForScan(settings)) {
                return postCallbackErrorOrReturn(callback,
                        ScanCallback.SCAN_FAILED_FEATURE_UNSUPPORTED);
            }
            if (!isHardwareResourcesAvailableForScan(settings)) {
                return postCallbackErrorOrReturn(callback,
                        ScanCallback.SCAN_FAILED_OUT_OF_HARDWARE_RESOURCES);
            }
            if (!isSettingsAndFilterComboAllowed(settings, filters)) {
                return postCallbackErrorOrReturn(callback,
                        ScanCallback.SCAN_FAILED_FEATURE_UNSUPPORTED);
            }
            if (callback != null) {
                BleScanCallbackWrapper wrapper = new BleScanCallbackWrapper(gatt, filters,
                        settings, workSource, callback, resultStorages);
                wrapper.startRegistration();
            } else {
                try {
                    gatt.startScanForIntent(callbackIntent, settings, filters,
                            ActivityThread.currentOpPackageName());
                } catch (RemoteException e) {
                    return ScanCallback.SCAN_FAILED_INTERNAL_ERROR;
                }
            }
        }
        return ScanCallback.NO_ERROR;
    }

    
Stops an ongoing Bluetooth LE scan.

Params:
  • callback – 
/**
     * Stops an ongoing Bluetooth LE scan.
     *
     * @param callback
     */
    @RequiresPermission(Manifest.permission.BLUETOOTH_ADMIN)
    public void stopScan(ScanCallback callback) {
        BluetoothLeUtils.checkAdapterStateOn(mBluetoothAdapter);
        synchronized (mLeScanClients) {
            BleScanCallbackWrapper wrapper = mLeScanClients.remove(callback);
            if (wrapper == null) {
                if (DBG) Log.d(TAG, "could not find callback wrapper");
                return;
            }
            wrapper.stopLeScan();
        }
    }

    
Stops an ongoing Bluetooth LE scan started using a PendingIntent. When creating the
PendingIntent parameter, please do not use the FLAG_CANCEL_CURRENT flag. Otherwise, the stop
scan may have no effect.

Params:
  • callbackIntent – The PendingIntent that was used to start the scan.
See Also:
/**
     * Stops an ongoing Bluetooth LE scan started using a PendingIntent. When creating the
     * PendingIntent parameter, please do not use the FLAG_CANCEL_CURRENT flag. Otherwise, the stop
     * scan may have no effect.
     *
     * @param callbackIntent The PendingIntent that was used to start the scan.
     * @see #startScan(List, ScanSettings, PendingIntent)
     */
    @RequiresPermission(Manifest.permission.BLUETOOTH_ADMIN)
    public void stopScan(PendingIntent callbackIntent) {
        BluetoothLeUtils.checkAdapterStateOn(mBluetoothAdapter);
        IBluetoothGatt gatt;
        try {
            gatt = mBluetoothManager.getBluetoothGatt();
            gatt.stopScanForIntent(callbackIntent, ActivityThread.currentOpPackageName());
        } catch (RemoteException e) {
        }
    }

    
Flush pending batch scan results stored in Bluetooth controller. This will return Bluetooth LE scan results batched on bluetooth controller. Returns immediately, batch scan results data will be delivered through the callback. 
Params:
  • callback – Callback of the Bluetooth LE Scan, it has to be the same instance as the one
used to start scan.
/**
     * Flush pending batch scan results stored in Bluetooth controller. This will return Bluetooth
     * LE scan results batched on bluetooth controller. Returns immediately, batch scan results data
     * will be delivered through the {@code callback}.
     *
     * @param callback Callback of the Bluetooth LE Scan, it has to be the same instance as the one
     * used to start scan.
     */
    public void flushPendingScanResults(ScanCallback callback) {
        BluetoothLeUtils.checkAdapterStateOn(mBluetoothAdapter);
        if (callback == null) {
            throw new IllegalArgumentException("callback cannot be null!");
        }
        synchronized (mLeScanClients) {
            BleScanCallbackWrapper wrapper = mLeScanClients.get(callback);
            if (wrapper == null) {
                return;
            }
            wrapper.flushPendingBatchResults();
        }
    }

    
Start truncated scan.

@hide
/**
     * Start truncated scan.
     *
     * @hide
     */
    @SystemApi
    public void startTruncatedScan(List<TruncatedFilter> truncatedFilters, ScanSettings settings,
            final ScanCallback callback) {
        int filterSize = truncatedFilters.size();
        List<ScanFilter> scanFilters = new ArrayList<ScanFilter>(filterSize);
        List<List<ResultStorageDescriptor>> scanStorages =
                new ArrayList<List<ResultStorageDescriptor>>(filterSize);
        for (TruncatedFilter filter : truncatedFilters) {
            scanFilters.add(filter.getFilter());
            scanStorages.add(filter.getStorageDescriptors());
        }
        startScan(scanFilters, settings, null, callback, null, scanStorages);
    }

    
Cleans up scan clients. Should be called when bluetooth is down.

@hide
/**
     * Cleans up scan clients. Should be called when bluetooth is down.
     *
     * @hide
     */
    public void cleanup() {
        mLeScanClients.clear();
    }

    
Bluetooth GATT interface callbacks

/**
     * Bluetooth GATT interface callbacks
     */
    private class BleScanCallbackWrapper extends IScannerCallback.Stub {
        private static final int REGISTRATION_CALLBACK_TIMEOUT_MILLIS = 2000;

        private final ScanCallback mScanCallback;
        private final List<ScanFilter> mFilters;
        private final WorkSource mWorkSource;
        private ScanSettings mSettings;
        private IBluetoothGatt mBluetoothGatt;
        private List<List<ResultStorageDescriptor>> mResultStorages;

        // mLeHandle 0: not registered
        // -2: registration failed because app is scanning to frequently
        // -1: scan stopped or registration failed
        // > 0: registered and scan started
        private int mScannerId;

        public BleScanCallbackWrapper(IBluetoothGatt bluetoothGatt,
                List<ScanFilter> filters, ScanSettings settings,
                WorkSource workSource, ScanCallback scanCallback,
                List<List<ResultStorageDescriptor>> resultStorages) {
            mBluetoothGatt = bluetoothGatt;
            mFilters = filters;
            mSettings = settings;
            mWorkSource = workSource;
            mScanCallback = scanCallback;
            mScannerId = 0;
            mResultStorages = resultStorages;
        }

        public void startRegistration() {
            synchronized (this) {
                // Scan stopped.
                if (mScannerId == -1 || mScannerId == -2) return;
                try {
                    mBluetoothGatt.registerScanner(this, mWorkSource);
                    wait(REGISTRATION_CALLBACK_TIMEOUT_MILLIS);
                } catch (InterruptedException | RemoteException e) {
                    Log.e(TAG, "application registeration exception", e);
                    postCallbackError(mScanCallback, ScanCallback.SCAN_FAILED_INTERNAL_ERROR);
                }
                if (mScannerId > 0) {
                    mLeScanClients.put(mScanCallback, this);
                } else {
                    // Registration timed out or got exception, reset RscannerId to -1 so no
                    // subsequent operations can proceed.
                    if (mScannerId == 0) mScannerId = -1;

                    // If scanning too frequently, don't report anything to the app.
                    if (mScannerId == -2) return;

                    postCallbackError(mScanCallback,
                            ScanCallback.SCAN_FAILED_APPLICATION_REGISTRATION_FAILED);
                }
            }
        }

        public void stopLeScan() {
            synchronized (this) {
                if (mScannerId <= 0) {
                    Log.e(TAG, "Error state, mLeHandle: " + mScannerId);
                    return;
                }
                try {
                    mBluetoothGatt.stopScan(mScannerId);
                    mBluetoothGatt.unregisterScanner(mScannerId);
                } catch (RemoteException e) {
                    Log.e(TAG, "Failed to stop scan and unregister", e);
                }
                mScannerId = -1;
            }
        }

        void flushPendingBatchResults() {
            synchronized (this) {
                if (mScannerId <= 0) {
                    Log.e(TAG, "Error state, mLeHandle: " + mScannerId);
                    return;
                }
                try {
                    mBluetoothGatt.flushPendingBatchResults(mScannerId);
                } catch (RemoteException e) {
                    Log.e(TAG, "Failed to get pending scan results", e);
                }
            }
        }

        
Application interface registered - app is ready to go

/**
         * Application interface registered - app is ready to go
         */
        @Override
        public void onScannerRegistered(int status, int scannerId) {
            Log.d(TAG, "onScannerRegistered() - status=" + status
                    + " scannerId=" + scannerId + " mScannerId=" + mScannerId);
            synchronized (this) {
                if (status == BluetoothGatt.GATT_SUCCESS) {
                    try {
                        if (mScannerId == -1) {
                            // Registration succeeds after timeout, unregister client.
                            mBluetoothGatt.unregisterClient(scannerId);
                        } else {
                            mScannerId = scannerId;
                            mBluetoothGatt.startScan(mScannerId, mSettings, mFilters,
                                    mResultStorages,
                                    ActivityThread.currentOpPackageName());
                        }
                    } catch (RemoteException e) {
                        Log.e(TAG, "fail to start le scan: " + e);
                        mScannerId = -1;
                    }
                } else if (status == ScanCallback.SCAN_FAILED_SCANNING_TOO_FREQUENTLY) {
                    // applicaiton was scanning too frequently
                    mScannerId = -2;
                } else {
                    // registration failed
                    mScannerId = -1;
                }
                notifyAll();
            }
        }

        
Callback reporting an LE scan result.

@hide
/**
         * Callback reporting an LE scan result.
         *
         * @hide
         */
        @Override
        public void onScanResult(final ScanResult scanResult) {
            if (VDBG) Log.d(TAG, "onScanResult() - " + scanResult.toString());

            // Check null in case the scan has been stopped
            synchronized (this) {
                if (mScannerId <= 0) return;
            }
            Handler handler = new Handler(Looper.getMainLooper());
            handler.post(new Runnable() {
                @Override
                public void run() {
                    mScanCallback.onScanResult(ScanSettings.CALLBACK_TYPE_ALL_MATCHES, scanResult);
                }
            });
        }

        @Override
        public void onBatchScanResults(final List<ScanResult> results) {
            Handler handler = new Handler(Looper.getMainLooper());
            handler.post(new Runnable() {
                @Override
                public void run() {
                    mScanCallback.onBatchScanResults(results);
                }
            });
        }

        @Override
        public void onFoundOrLost(final boolean onFound, final ScanResult scanResult) {
            if (VDBG) {
                Log.d(TAG, "onFoundOrLost() - onFound = " + onFound + " " + scanResult.toString());
            }

            // Check null in case the scan has been stopped
            synchronized (this) {
                if (mScannerId <= 0) {
                    return;
                }
            }
            Handler handler = new Handler(Looper.getMainLooper());
            handler.post(new Runnable() {
                @Override
                public void run() {
                    if (onFound) {
                        mScanCallback.onScanResult(ScanSettings.CALLBACK_TYPE_FIRST_MATCH,
                                scanResult);
                    } else {
                        mScanCallback.onScanResult(ScanSettings.CALLBACK_TYPE_MATCH_LOST,
                                scanResult);
                    }
                }
            });
        }

        @Override
        public void onScanManagerErrorCallback(final int errorCode) {
            if (VDBG) {
                Log.d(TAG, "onScanManagerErrorCallback() - errorCode = " + errorCode);
            }
            synchronized (this) {
                if (mScannerId <= 0) {
                    return;
                }
            }
            postCallbackError(mScanCallback, errorCode);
        }
    }

    private int postCallbackErrorOrReturn(final ScanCallback callback, final int errorCode) {
        if (callback == null) {
            return errorCode;
        } else {
            postCallbackError(callback, errorCode);
            return ScanCallback.NO_ERROR;
        }
    }

    private void postCallbackError(final ScanCallback callback, final int errorCode) {
        mHandler.post(new Runnable() {
            @Override
            public void run() {
                callback.onScanFailed(errorCode);
            }
        });
    }

    private boolean isSettingsConfigAllowedForScan(ScanSettings settings) {
        if (mBluetoothAdapter.isOffloadedFilteringSupported()) {
            return true;
        }
        final int callbackType = settings.getCallbackType();
        // Only support regular scan if no offloaded filter support.
        if (callbackType == ScanSettings.CALLBACK_TYPE_ALL_MATCHES
                && settings.getReportDelayMillis() == 0) {
            return true;
        }
        return false;
    }

    private boolean isSettingsAndFilterComboAllowed(ScanSettings settings,
            List<ScanFilter> filterList) {
        final int callbackType = settings.getCallbackType();
        // If onlost/onfound is requested, a non-empty filter is expected
        if ((callbackType & (ScanSettings.CALLBACK_TYPE_FIRST_MATCH
                | ScanSettings.CALLBACK_TYPE_MATCH_LOST)) != 0) {
            if (filterList == null) {
                return false;
            }
            for (ScanFilter filter : filterList) {
                if (filter.isAllFieldsEmpty()) {
                    return false;
                }
            }
        }
        return true;
    }

    private boolean isHardwareResourcesAvailableForScan(ScanSettings settings) {
        final int callbackType = settings.getCallbackType();
        if ((callbackType & ScanSettings.CALLBACK_TYPE_FIRST_MATCH) != 0
                || (callbackType & ScanSettings.CALLBACK_TYPE_MATCH_LOST) != 0) {
            // For onlost/onfound, we required hw support be available
            return (mBluetoothAdapter.isOffloadedFilteringSupported()
                    && mBluetoothAdapter.isHardwareTrackingFiltersAvailable());
        }
        return true;
    }
}