onLeScan function not called when trying to detect BLE devices

问题

I am trying to detect nearby Bluetooth Low-Energy devices on a service. When the service is started, startLeScan() is called, and then stopLeScan() is called after 10 seconds. Even though startLeScan() returns true, and I didn't get any error, onLeScan on the LeScanCallback was not called. the Service:

    .
    .
    .
            // Device scan callback.
        private BluetoothAdapter.LeScanCallback mLeScanCallback =
                new BluetoothAdapter.LeScanCallback() {

                    public void onLeScan(final BluetoothDevice device, final int rssi, final byte[] scanRecord) {
                        Log.i(TAG, "New LE Device: " + device.getName() + " @ " + rssi);
                        if (DEVICE_NAME.equals(device.getName()) && deviceAddress.equals(device.getAddress())) {
                            mDevice = device;
                            BleScan(false);
                            connectBluetoothDevice();
                        }
                    }
                };

    /**
     * Starts and stops Bluetooth LE scanning for BLE devices.
     *
     * @param enable true to start scanning, false to stop scanning.
     */
    public void scanLeDevice(final boolean enable) {
        if (enable) {
            // Stops scanning after a pre-defined scan period.
            mHandler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    if (mScanning) {
                        BleScan(false);
                    }
                }
            }, SCAN_PERIOD);
            BleScan(true);
        } else {
            BleScan(false);
        }

    }

    /**
     * @param scan true to scan, and false to stop scanning for Bluetooth LE devices.
     */
    private void BleScan(boolean scan) {
        if (scan) {
            mScanning = true;
            boolean temp = mBluetoothAdapter.startLeScan(mLeScanCallback);
            Log.i(TAG, "Started LE scan: " + temp);
        } else {
            mScanning = false;
            mBluetoothAdapter.stopLeScan(mLeScanCallback);
        }
    }

I tried to use BluetoothLeScanner startScan() and stopScan(), and using ScanCallback instead, but it didn't help:

    ScanCallback mScanCallback = new ScanCallback() {
        @Override
        public void onScanResult(int callbackType, ScanResult result) {
            Log.i(TAG, "New LE Device: " + result.getDevice().getName() + " @ " + result.getRssi());
        }

        @Override
        public void onScanFailed(int errorCode) {
            Log.i(TAG, "Scan Faild!!");
        }
    };


    /**
     * Starts and stops Bluetooth LE scanning for BLE devices.
     *
     * @param enable true to start scanning, false to stop scanning.
     */
    public void scanLeDevice(final boolean enable) {
        if (enable) {
            // Stops scanning after a pre-defined scan period.
            mHandler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    if (mScanning) {
                        BleScan(false);
                    }
                }
            }, SCAN_PERIOD);
            BleScan(true);
        } else {
            BleScan(false);
        }

    }

    /**
     * @param scan true to scan, and false to stop scanning for Bluetooth LE devices.
     */
    private void BleScan(boolean scan) {
        if (scan) {
            mScanning = true;
            mBluetoothLeScanner.startScan(mScanCallback);
            Log.i(TAG, "Started LE scan");
        } else {
            mScanning = false;
            mBluetoothLeScanner.stopScan(mScanCallback);
        }
    }

some say GPS needs to be turned on, so I turned on GPS. I tried rebooting the android device. Another BLE detection app can see the BLE device.

Why isn't the scan callback called?

Edit

I'm running this app on a nexus 5 device running Android 6.0.1 .

I tried adding location permission, but it didn't help:

( uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" )

回答1:

I have similar problem. Same code, one tablet not work but other does. I have no solution but when I reset my tablet and reinstall apk, it's can work fine again.

I found this onLeScan from BluetoothAdapter.LeScanCallback not called in Android Marshmallow when I open gps, it's work...

回答2:

Try to switch on the access to location data in app settings (Settings -> Applications -> Your App -> Rules -> Location Data)

来源：https://stackoverflow.com/questions/36888827/onlescan-function-not-called-when-trying-to-detect-ble-devices