BluetoothLeScanner.startScan with Android 6.0 does not discover devices

Question

I'm trying to use the function BluatoothLeScanner.startScan instead of the deprecated one BluetoothAdapter.startLeScan. Yesterday I updated my Nexus 5 to Android 6.0 and since that moment my app does not work anymore. I firstly add the preferences required ACCESS_COARSE_LOCATION as found here, https://developer.android.com/about/versions/marshmallow/android-6.0-changes.html#behavior-hardware-id. Then I added the permission as described here: https://developer.android.com/training/permissions/requesting.html. But at the end it seems not working, it does not send back the ble devices.

This is my code:

manifest

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="com.stm.sensitronapp">
          <uses-sdk android:maxSdkVersion="23"/>
          <uses-feature android:name="android.hardware.bluetooth_le" android:required="true"/>

          <uses-permission android:name="android.permission.BLUETOOTH"/>
          <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
          <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>`

DeviceScanActivity

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
...

if (ContextCompat.checkSelfPermission(this,Manifest.permission.ACCESS_COARSE_LOCATION)
            != PackageManager.PERMISSION_GRANTED){
        if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                Manifest.permission.ACCESS_COARSE_LOCATION)) {
        } else {
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.ACCESS_COARSE_LOCATION},
                    MY_PERMISSIONS_REQUEST_ACCESS_COARSE);
        }
    }

// Device scan callback.
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
        if (ContextCompat.checkSelfPermission(this,Manifest.permission.ACCESS_COARSE_LOCATION)
                == PackageManager.PERMISSION_GRANTED) {
            mScanCallback = new ScanCallback() {
                @Override
                public void onScanResult(int callbackType, ScanResult result) {
                    super.onScanResult(callbackType, result);
                    mLeDeviceListAdapter.addDevice(result.getDevice());
                    mLeDeviceListAdapter.notifyDataSetChanged();
                }
            };
        }
    } 
}
final BluetoothManager bluetoothManager =
            (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = bluetoothManager.getAdapter();

if (mBluetoothAdapter.getState() == BluetoothAdapter.STATE_ON) {
        mSwipeRefreshLayout.setRefreshing(true);
        mLeDeviceListAdapter.clear();
        mBluetoothLeScanner = mBluetoothAdapter.getBluetoothLeScanner();
        if(ContextCompat.checkSelfPermission(this,
                    Manifest.permission.ACCESS_COARSE_LOCATION ) == PackageManager.PERMISSION_GRANTED) {
                mBluetoothLeScanner.startScan(mScanCallback);
            }
        }

EDIT: to solve this problem I only turned on the GPS. It is easy to do it programmatically in this way.

Answer 1

if permissions granted, have a try: turn ON the GPS.