android: Bluetooth won't discover devices

Question

I'm writing an Android-App, which is supposed to discover devices via Bluetooth.

I don't get any exceptions, but the devices are just not found, even though my windows pc finds them (and can be found itself).

I'm certain they are BLE, but I tried both ways. And of course I tried them separately.

Here is my ListActivity, which searches for the devices:

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

    mHandler = new Handler();

    setContentView(R.layout.bluetooth_list_view);
    listView = getListView();

    if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
        Toast.makeText(this, "BLE is not supported", Toast.LENGTH_SHORT).show();
        finish();
    }

    final BluetoothManager bluetoothManager =
            (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
    mBluetoothAdapter = bluetoothManager.getAdapter();
    mBluetoothLeScanner = mBluetoothAdapter.getBluetoothLeScanner();
    Log.d(TAG, "on Create start5");

    if (mBluetoothAdapter == null) {
        Toast.makeText(this, "BLE is not supported", Toast.LENGTH_SHORT).show();
        finish();
        return;
    }

    mLeDeviceListAdapter = new LeDeviceListAdapter(this);
    setListAdapter(mLeDeviceListAdapter);
    listView.setAdapter(mLeDeviceListAdapter);

    IntentFilter filter = new IntentFilter(); 
    filter.addAction(BluetoothDevice.ACTION_FOUND);
    filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_STARTED);
    filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);

    registerReceiver(mReceiver, filter);
    mBluetoothAdapter.startDiscovery(); 
}    

private void scanLeDevice(final boolean enable) {
    Log.e(TAG, "scanLeDevice: " + enable);
    if (enable) {
        // Stops scanning after a pre-defined scan period.
        mHandler.postDelayed(new Runnable() {
            @Override
            public void run() {
                Log.e(TAG, "after Scan mLeDeviceListAdapter: " + mLeDeviceListAdapter.getCount());
                Log.e(TAG, "after Scan isEmpty(): " + mLeDeviceListAdapter.isEmpty());
                mScanning = false;
                mBluetoothLeScanner.stopScan(mScanCallback);
                invalidateOptionsMenu();
            }
        }, SCAN_PERIOD);

        mScanning = true;
        mBluetoothLeScanner.startScan(mScanCallback);

    } else {
        mScanning = false;
        mBluetoothLeScanner.stopScan(mScanCallback);
    }
    invalidateOptionsMenu();
}

The logs say after Scan mLeDeviceListAdapter: 0 and after Scan isEmpty(): true.

ScanCallback mScanCallback = new ScanCallback() {
    @Override
    public void onScanResult(int callbackType, ScanResult result) {
        Log.e(TAG, "onScanResult: " + result);
        super.onScanResult(callbackType, result);
        mLeDeviceListAdapter.addDevice(result.getDevice());
        mLeDeviceListAdapter.notifyDataSetChanged();
    }
};

That log (onScanResult) is never called.

And for not BLE: private final BroadcastReceiver mReceiver = new BroadcastReceiver() { //TODO not ble example public void onReceive(Context context, Intent intent) { String action = intent.getAction();

        if (BluetoothAdapter.ACTION_DISCOVERY_STARTED.equals(action)) {
            Log.e(TAG, "Not BLE discovry starts");
            //discovery starts, we can show progress dialog or perform other tasks
        } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
            Log.e(TAG, "Not BLE discovry finishes");
            //discovery finishes, dismis progress dialog
        } else if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            //bluetooth device found
            BluetoothDevice device = (BluetoothDevice) intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);

            Log.e(TAG, "Found device " + device.getName());
        }
    }
};

Not BLE discovry finishes is printed and so is Not BLE discovry starts. Found device is never printed. But I'm positiv that the devices are BLE.

I have the necessary permissions in my manifest:

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

What am I doing wrong?

Edit: i really need help. Thinks I tried/checked so far:

Enabled Bluetooth adapter.
Bluetooth usage permissions granted.
Location permission (ACCESS_COARSE and ACCESS_FINE) granted.
Made sure gps provider is enabled (Smartphone GPS settings).

Lala Lala · Accepted Answer · 2019-06-19T16:11:58

Maybe because you didn't request ACCESS_COARSE_LOCATION in onCreate

This project is a good resource for you to start your Bluetooth scanner:

https://github.com/joelwass/Android-BLE-Scan-Example

android: Bluetooth won't discover devices

1 Answers