java - 如何启用通知并能够读取我的 BLE 代码？

Question

所以我有一个秤，它通过 BLE UUID 0xFFF4 发送重量数据。当我打开通知时，它与应用程序 nRF Connect 一起工作，我看到了数据。

但是，我无法在自己的应用程序中获取它。我有读取 0xFFF4 特征数据的代码，我按照教程进行了操作，但我不确定如何在 0xFFF4 上设置通知并接收数据。

我修改实现的代码在最下面，这里service是0xFFF0，read是0xFFF4。它适用于读取秤的任何其他特征，例如名称，但我无法获取重量数据，我认为这是因为我必须设置通知，但我不知道如何操作。

/**
* Service for managing connection and data communication with a GATT server hosted on a
* given Bluetooth LE device.
*/
public class BluetoothLeService extends Service {
private final static String TAG = BluetoothLeService.class.getSimpleName();

private BluetoothManager mBluetoothManager;
private BluetoothAdapter mBluetoothAdapter;
private String mBluetoothDeviceAddress;
private BluetoothGatt mBluetoothGatt;
private int mConnectionState = STATE_DISCONNECTED;

private static final int STATE_DISCONNECTED = 0;
private static final int STATE_CONNECTING = 1;
private static final int STATE_CONNECTED = 2;

public final static String ACTION_GATT_CONNECTED =
        "com.example.bluetooth.le.ACTION_GATT_CONNECTED";
public final static String ACTION_GATT_DISCONNECTED =
        "com.example.bluetooth.le.ACTION_GATT_DISCONNECTED";
public final static String ACTION_GATT_SERVICES_DISCOVERED =
        "com.example.bluetooth.le.ACTION_GATT_SERVICES_DISCOVERED";
public final static String ACTION_DATA_AVAILABLE =
        "com.example.bluetooth.le.ACTION_DATA_AVAILABLE";
public final static String EXTRA_DATA =
        "com.example.bluetooth.le.EXTRA_DATA";

public final static UUID UUID_HEART_RATE_MEASUREMENT =
        UUID.fromString(SampleGattAttributes.HEART_RATE_MEASUREMENT);

// Implements callback methods for GATT events that the app cares about.  For example,
// connection change and services discovered.
private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
    @Override
    public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
        String intentAction;
        if (newState == BluetoothProfile.STATE_CONNECTED) {
            intentAction = ACTION_GATT_CONNECTED;
            mConnectionState = STATE_CONNECTED;
            broadcastUpdate(intentAction);
            Log.i(TAG, "Connected to GATT server.");
            // Attempts to discover services after successful connection.
            Log.i(TAG, "Attempting to start service discovery:" +
                    mBluetoothGatt.discoverServices());

        } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
            intentAction = ACTION_GATT_DISCONNECTED;
            mConnectionState = STATE_DISCONNECTED;
            Log.i(TAG, "Disconnected from GATT server.");
            broadcastUpdate(intentAction);
        }
    }

    @Override
    public void onServicesDiscovered(BluetoothGatt gatt, int status) {
        if (status == BluetoothGatt.GATT_SUCCESS) {
            broadcastUpdate(ACTION_GATT_SERVICES_DISCOVERED);
        } else {
            Log.w(TAG, "onServicesDiscovered received: " + status);
        }
    }

    @Override
    public void onCharacteristicRead(BluetoothGatt gatt,
                                     BluetoothGattCharacteristic characteristic,
                                     int status) {
        if (status == BluetoothGatt.GATT_SUCCESS) {
            broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
        }
    }

    @Override
    public void onCharacteristicChanged(BluetoothGatt gatt,
                                        BluetoothGattCharacteristic characteristic) {
        broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
    }
};

private void broadcastUpdate(final String action) {
    final Intent intent = new Intent(action);
    sendBroadcast(intent);
}

private void broadcastUpdate(final String action,
                             final BluetoothGattCharacteristic characteristic) {
    final Intent intent = new Intent(action);

    // This is special handling for the Heart Rate Measurement profile.  Data parsing is
    // carried out as per profile specifications:
    // http://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.heart_rate_measurement.xml
    if (UUID_HEART_RATE_MEASUREMENT.equals(characteristic.getUuid())) {
        int flag = characteristic.getProperties();
        int format = -1;
        if ((flag & 0x01) != 0) {
            format = BluetoothGattCharacteristic.FORMAT_UINT16;
            Log.d(TAG, "Heart rate format UINT16.");
        } else {
            format = BluetoothGattCharacteristic.FORMAT_UINT8;
            Log.d(TAG, "Heart rate format UINT8.");
        }
        final int heartRate = characteristic.getIntValue(format, 1);
        Log.d(TAG, String.format("Received heart rate: %d", heartRate));
        intent.putExtra(EXTRA_DATA, String.valueOf(heartRate));
    } else {
        // For all other profiles, writes the data formatted in HEX.
        final byte[] data = characteristic.getValue();
        if (data != null && data.length > 0) {
            final StringBuilder stringBuilder = new StringBuilder(data.length);
            for(byte byteChar : data)
                stringBuilder.append(String.format("%02X ", byteChar));
            intent.putExtra(EXTRA_DATA, new String(data) + "\n" + stringBuilder.toString());
        }
    }
    sendBroadcast(intent);
}

public class LocalBinder extends Binder {
    BluetoothLeService getService() {
        return BluetoothLeService.this;
    }
}

@Override
public IBinder onBind(Intent intent) {
    return mBinder;
}

@Override
public boolean onUnbind(Intent intent) {
    // After using a given device, you should make sure that BluetoothGatt.close() is called
    // such that resources are cleaned up properly.  In this particular example, close() is
    // invoked when the UI is disconnected from the Service.
    close();
    return super.onUnbind(intent);
}

private final IBinder mBinder = new LocalBinder();

/**
 * Initializes a reference to the local Bluetooth adapter.
 *
 * @return Return true if the initialization is successful.
 */
public boolean initialize() {
    // For API level 18 and above, get a reference to BluetoothAdapter through
    // BluetoothManager.
    if (mBluetoothManager == null) {
        mBluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
        if (mBluetoothManager == null) {
            Log.e(TAG, "Unable to initialize BluetoothManager.");
            return false;
        }
    }

    mBluetoothAdapter = mBluetoothManager.getAdapter();
    if (mBluetoothAdapter == null) {
        Log.e(TAG, "Unable to obtain a BluetoothAdapter.");
        return false;
    }

    return true;
}

/**
 * Connects to the GATT server hosted on the Bluetooth LE device.
 *
 * @param address The device address of the destination device.
 *
 * @return Return true if the connection is initiated successfully. The connection result
 *         is reported asynchronously through the
 *         {@code BluetoothGattCallback#onConnectionStateChange(android.bluetooth.BluetoothGatt, int, int)}
 *         callback.
 */
public boolean connect(final String address) {
    if (mBluetoothAdapter == null || address == null) {
        Log.w(TAG, "BluetoothAdapter not initialized or unspecified address.");
        return false;
    }

    // Previously connected device.  Try to reconnect.
    if (mBluetoothDeviceAddress != null && address.equals(mBluetoothDeviceAddress)
            && mBluetoothGatt != null) {
        Log.d(TAG, "Trying to use an existing mBluetoothGatt for connection.");
        if (mBluetoothGatt.connect()) {
            mConnectionState = STATE_CONNECTING;
            return true;
        } else {
            return false;
        }
    }

    final BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
    if (device == null) {
        Log.w(TAG, "Device not found.  Unable to connect.");
        return false;
    }
    // We want to directly connect to the device, so we are setting the autoConnect
    // parameter to false.
    mBluetoothGatt = device.connectGatt(this, false, mGattCallback);
    Log.d(TAG, "Trying to create a new connection.");
    mBluetoothDeviceAddress = address;
    mConnectionState = STATE_CONNECTING;
    return true;
}

/**
 * Disconnects an existing connection or cancel a pending connection. The disconnection result
 * is reported asynchronously through the
 * {@code BluetoothGattCallback#onConnectionStateChange(android.bluetooth.BluetoothGatt, int, int)}
 * callback.
 */
public void disconnect() {
    if (mBluetoothAdapter == null || mBluetoothGatt == null) {
        Log.w(TAG, "BluetoothAdapter not initialized");
        return;
    }
    mBluetoothGatt.disconnect();
}

/**
 * After using a given BLE device, the app must call this method to ensure resources are
 * released properly.
 */
public void close() {
    if (mBluetoothGatt == null) {
        return;
    }
    mBluetoothGatt.close();
    mBluetoothGatt = null;
}

/**
 * Request a read on a given {@code BluetoothGattCharacteristic}. The read result is reported
 * asynchronously through the {@code BluetoothGattCallback#onCharacteristicRead(android.bluetooth.BluetoothGatt, android.bluetooth.BluetoothGattCharacteristic, int)}
 * callback.
 *
 * @param characteristic The characteristic to read from.
 */
public void readCharacteristic(BluetoothGattCharacteristic characteristic) {
    if (mBluetoothAdapter == null || mBluetoothGatt == null) {
        Log.w(TAG, "BluetoothAdapter not initialized");
        return;
    }
    mBluetoothGatt.readCharacteristic(characteristic);
}

/**
 * Enables or disables notification on a give characteristic.
 *
 * @param characteristic Characteristic to act on.
 * @param enabled If true, enable notification.  False otherwise.
 */
public void setCharacteristicNotification(BluetoothGattCharacteristic characteristic,
                                          boolean enabled) {
    if (mBluetoothAdapter == null || mBluetoothGatt == null) {
        Log.w(TAG, "BluetoothAdapter not initialized");
        return;
    }
    mBluetoothGatt.setCharacteristicNotification(characteristic, enabled);

    // This is specific to Heart Rate Measurement.
    if (UUID_HEART_RATE_MEASUREMENT.equals(characteristic.getUuid())) {
        BluetoothGattDescriptor descriptor = characteristic.getDescriptor(
                UUID.fromString(SampleGattAttributes.CLIENT_CHARACTERISTIC_CONFIG));
        descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
        mBluetoothGatt.writeDescriptor(descriptor);
    }
}

/**
 * Retrieves a list of supported GATT services on the connected device. This should be
 * invoked only after {@code BluetoothGatt#discoverServices()} completes successfully.
 *
 * @return A {@code List} of supported services.
 */
public List<BluetoothGattService> getSupportedGattServices() {
    if (mBluetoothGatt == null) return null;

    return mBluetoothGatt.getServices();
}

public void readCustomCharacteristic() {
    if (mBluetoothAdapter == null || mBluetoothGatt == null) {
        Log.w(TAG, "BluetoothAdapter not initialized");
        return;
    }
    /*check if the service is available on the device*/
    BluetoothGattService mCustomService = mBluetoothGatt.getService(UUID.fromString("0000fff0-0000-1000-8000-00805f9b34fb"));
    if(mCustomService == null){
        Log.w(TAG, "Custom BLE Service not found");
        return;
    }
    /*get the read characteristic from the service*/
    BluetoothGattCharacteristic mReadCharacteristic = mCustomService.getCharacteristic(UUID.fromString("0000fff4-0000-1000-8000-00805f9b34fb"));
    if(mBluetoothGatt.readCharacteristic(mReadCharacteristic) == false){
        Log.w(TAG, "Failed to read characteristic");
    }
}



}

几个月来我一直在努力让它发挥作用，但 BLE 实在太难理解了，而且没有简单的实现指南，这是一个很大的痛苦。如果有人可以提供帮助，将不胜感激。非常感谢。

编辑:我想我必须添加

BluetoothGattDescriptor descriptor = mCustomService.getCharacteristic(UUID.fromString("0000fff4-0000-1000-8000-00805f9b34fb")).getDescriptor(
                UUID.fromString(SampleGattAttributes.CLIENT_CHARACTERISTIC_CONFIG));
        descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
        mBluetoothGatt.writeDescriptor(descriptor);

但它似乎不起作用，我收到错误。谢谢。

Answer 1

这是我的 setNotifications() 方法，它在我的代码中运行良好:

public void setNotifications() {
    BluetoothGattService service = bluetoothGatt.getService(SERVICE_UUID);
    BluetoothGattCharacteristic characteristic = service.getCharacteristic(CHARACTERISTIC_UUID);

    BluetoothGattDescriptor descriptor = characteristic.getDescriptor(DESCRIPTOR_UUID);
    descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
    characteristic.addDescriptor(descriptor);
    characteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE);
    bluetoothGatt.writeDescriptor(descriptor);

    bluetoothGatt.setCharacteristicNotification(characteristic, true);
}

希望对您有所帮助。