如何从 BLE 设备读取数据

Question

So, I have been struggling for some time now with this BLE. I am working on an Appcelerator module that can enable communication (read/write data) from some devices with an Android tablet. I am able to scan, discover devices, connect to it and discover it's services. What I am unable to do is to read data. As you can see on the below code, the contents on method readData() ALWAYS return false. (writeDescriptor, readCharacteristic, readDescriptor). No matter what, this always returns false. The callback is never called, and I am completely stuck. What on earth am I doing wrong? How can I set those stuff on readData() to be true, and what to do after that? Thank you all in advance!

I have checked stackOverflow many many times and tried lots of solutions proposed here, but nothing seems to work. As far as I understood, my steps are correct. Something is missing... Just don't know what...

public class AndroidbleModule extends KrollModule  {

    private BluetoothManager btManager;
    private BluetoothAdapter btAdapter;
    private BluetoothDevice btDevice;
    private TiApplication appContext;
    private Activity activity;
    private BluetoothLeScanner btScanner;

    public AndroidbleModule() {
        super();
        appContext = TiApplication.getInstance();
        activity = appContext.getCurrentActivity();
        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        filter.addAction(BluetoothDevice.ACTION_UUID);
        filter.addAction(BluetoothDevice.ACTION_FOUND);
        filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_STARTED);
        filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
        filter.addAction(BluetoothAdapter.ACTION_STATE_CHANGED);
        filter.addAction(BluetoothDevice.ACTION_BOND_STATE_CHANGED);
        appContext.registerReceiver(new BlutoothStateChangedBroadcastReceiver(AndroidbleModule.this, btAdapter),
                filter);
    }

    private BluetoothGatt bluetoothGatt;
    private BluetoothGattCallbackHandler btGattHandler = new BluetoothGattCallbackHandler(AndroidbleModule.this);

    @Kroll.method
    public void connectToDevice(String device) {

        if (bluetoothGatt != null) {
            bluetoothGatt.disconnect();
        }
        for (String devName : btDevices.keySet()) {

            if(device.equals(devName)) {
                BluetoothDevice deviceAddress = btDevices.get(devName);
                bluetoothGatt = deviceAddress.connectGatt(appContext, false, btGattHandler);
                bluetoothGatt.connect();
                bluetoothGatt.discoverServices();
                deviceAddress.createBond();
                deviceAddress.getBondState();   
                btDevice = deviceAddress;
            }
        }
    }
    BluetoothGattCharacteristic charac;
    BluetoothGattDescriptor desc;

    @Kroll.method
    public void setNotifications() {
        List<BluetoothGattService> btGattServicesList = bluetoothGatt.getServices();
        List<BluetoothGattCharacteristic> btGattCharList = btGattServicesList.get(2).getCharacteristics();
        List<BluetoothGattDescriptor> btDescList = btGattCharList.get(1).getDescriptors();
        BluetoothGattCharacteristic characteristic = btGattCharList.get(1);
        BluetoothGattDescriptor descriptor = btDescList.get(0);

        bluetoothGatt.setCharacteristicNotification(characteristic, true);
        descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);

        charac = characteristic;
        desc = descriptor;
    }

    @Kroll.method
    public void readData() {
        bluetoothGatt.writeDescriptor(desc);
        bluetoothGatt.readCharacteristic(charac);
        bluetoothGatt.readDescriptor(desc);
    }

    private Set<String> devSet = new LinkedHashSet<String>();

    HashMap<String, BluetoothDevice> btDevices = new HashMap<String, BluetoothDevice>();

    private ScanCallback scanCallback = new ScanCallback() {
        @Override
        public void onScanResult(int callbackType, ScanResult result) {

            BluetoothDevice device;
            device = result.getDevice();

            KrollDict kd = new KrollDict();
            kd.put("name", device.getName());
            kd.put("address", device.getAddress());

            System.out.println("Devices Found on Scan: " + kd.toString());

            btDevice = device;
            devSet.add(device.getName());
            btDevices.put(device.getName(), device);
        }
    };

    @Kroll.method
    public void startScanning(@Kroll.argument(optional = true) int _scanmode) {
        if (btAdapter != null) {
            btScanner = btAdapter.getBluetoothLeScanner();
            btScanner.startScan(scanCallback);
            isScanning = true;
        }
    }
}

Answer 1

First, my connectToDevice() method, with the changes mentioned:

public void connectToDevice(String device) {
    if (bluetoothGatt != null) {
        bluetoothGatt.disconnect();
    }
    for (String devName : btDevices.keySet()) {

        if(device.equals(devName)) {
            BluetoothDevice deviceAddress = btDevices.get(devName);
            bluetoothGatt = deviceAddress.connectGatt(appContext, false, btGattHandler);
            btDevice = deviceAddress;
        }
    }
}

The onConnectionStateChanged() callback method:

public void onConnectionStateChange(final BluetoothGatt gatt,
        final int status, final int newState) {
    gatt.getDevice().createBond();
    KrollDict kd = new KrollDict();
    kd.put("newState", newState);
    kd.put("status", status);
    if (proxy.hasListeners("didConnectionStateChange")) {
        proxy.fireEvent("didConnectionStateChange", kd);
    }
    gatt.discoverServices();
}

The onServicesDiscovered() callback method:

public void onServicesDiscovered(final BluetoothGatt gatt, final int status) {
    BluetoothDevice device = gatt.getDevice();
    KrollDict kdServices = new KrollDict();
    KrollDict kdCharacteristics = new KrollDict();

    List<BluetoothGattService> services = gatt.getServices();
    kdServices.put("device", device.getAddress());
    kdCharacteristics.put("device", device.getAddress());

    Log.i(LCAT, device.getAddress() + " services count: " + services.size());

    ArrayList<Object> listServices = new ArrayList<>();
    HashMap<String, Object> hashChar = new HashMap<String, Object>();

    for (BluetoothGattService service : services) {
        Log.i(LCAT,
                "Service: " + service.getType() + " " + service.getUuid());

        HashMap<String, Object> listService = new HashMap<String, Object>();
        listService.put("serviceType", service.getType());
        listService.put("serviceUuid", service.getUuid());
        listServices.add(listService);

        ArrayList<HashMap<String, Object>> listChars = new ArrayList<HashMap<String, Object>>();
        List<BluetoothGattCharacteristic> characteristics = service
                .getCharacteristics();
        for (BluetoothGattCharacteristic btc : characteristics) {
            Log.i(LCAT, "uuid: " + btc.getUuid());

            HashMap<String, Object> listChar = new HashMap<String, Object>();
            listChar.put("uuid", btc.getUuid());
            listChar.put("value", btc.getValue());

            listChars.add(listChar);
            // TODO not needed at the moment
             byte[] data = btc.getValue();
             if (data != null && data.length > 0) {
             final StringBuilder stringBuilder = new
             StringBuilder(data.length);
             for (byte byteChar : data) {
             stringBuilder.append(String.format("%02X ", byteChar));
             }

             Log.i(LCAT, "String val: " + btc.getUuid() + " " +
             btc.getValue() + " " + stringBuilder.toString());
             }
            gatt.readCharacteristic(btc);
        }
        hashChar.put("serviceUuid", service.getUuid());
        hashChar.put("chars", listChars);
    }
    if (proxy.hasListeners("didDiscoverServices"))
        proxy.fireEvent("didDiscoverServices", kdServices);
    if (proxy.hasListeners("didDiscoverCharacteristicsForService"))
        proxy.fireEvent("didDiscoverCharacteristicsForService",
                kdCharacteristics);
    System.out.println("Services successfully discovered!");
}

The setNotifications() I've left untouched, and as you can see, it's returning true for everything. Now, when I call readData() (just left one gatt call, which is writeCharacteristic()), it returns false, as seen in the last line of the log. Check it out.

The Log:

I/System.out: connectToDevice() called!
I/System.out: Device successfully connected!

BluetoothDevice: createBond() for device FA:45:B9:7C:86:7C called by pid: 6194 tid: 6207

BLE: (Binder:6194_2) [19078,19078] FA:45:B9:7C:86:7C services count: 3
BLE: (Binder:6194_2) [1,19079] Service: 0 00001800-0000-1000-8000-00805f9b34fb
BLE: (Binder:6194_2) [0,19079] uuid: 00002a00-0000-1000-8000-00805f9b34fb
BLE: (Binder:6194_2) [1,19080] uuid: 00002a01-0000-1000-8000-00805f9b34fb
BLE: (Binder:6194_2) [0,19080] uuid: 00002a04-0000-1000-8000-00805f9b34fb
BLE: (Binder:6194_2) [1,19081] uuid: 00002aa6-0000-1000-8000-00805f9b34fb
BLE: (Binder:6194_2) [0,19081] Service: 0 00001801-0000-1000-8000-00805f9b34fb
BLE: (Binder:6194_2) [0,19081] Service: 0 6e400001-b5a3-f393-e0a9-e50e24dcca9e
BLE: (Binder:6194_2) [0,19081] uuid: 6e400002-b5a3-f393-e0a9-e50e24dcca9e
BLE: (Binder:6194_2) [0,19081] uuid: 6e400003-b5a3-f393-e0a9-e50e24dcca9e
I/System.out: Services successfully discovered!

I/System.out: btGattServicesList - [android.bluetooth.BluetoothGattService@c893553, android.bluetooth.BluetoothGattService@5dd2e90, android.bluetooth.BluetoothGattService@6bce389]
I/System.out: btGattCharList - [android.bluetooth.BluetoothGattCharacteristic@b6cf8e, android.bluetooth.BluetoothGattCharacteristic@6e7d3af]
I/System.out: btDescList - [android.bluetooth.BluetoothGattDescriptor@b8ea3bc]

I/System.out: setCharacteristicNotification = true
I/System.out: Enable Notification Value = true
I/System.out: characteristic.addDescriptor(descriptor) = true

I/System.out: bluetoothGatt.writeCharacteristic(charac) false

What the hell is missing or going wrong here?

Answer 2

So, after a lot of time wasted, I figured it out. setNotifications is only the first step. We must tell the device to start streaming data so the App can collect it. It is done via bluetoothGatt.writeCharacteristic(characteristic) After we proper set the writings, of course. With this done, the bytes just keep coming! =)