为 BLE Scale 编写应用程序代码 - 包括所有信息

Question

我正在尝试编写一个 BLE 应用程序，该应用程序从 BLE 秤获取体重数据并将其显示在应用程序上。

关于秤的一些信息：

• 服务在 UUID 0XFFF0 上，重量数据特征在 UUID 0XFFF4 上。

• 我需要在 0XFFF4 上启用通知才能接收数据。

• 接收数据的形式是一个 32 字节的数组。

  比如我站在秤上，它就会发出来

  00 00 00 00 02 02 00 00 00 00 00 00 00 00 00 00

• 权重数据在字节 5 和 6 上。如果转换字节 5 和 6 的十六进制值，在该示例中为 '0202'，它将变为十进制的 514。

我现在所拥有的，我已经编写了几个星期的代码，我将 Scale UUID 替换为。

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 WEIGHT_MEASUREMENT =
        UUID.fromString(SampleGattAttributes.WEIGHT);

// 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 (WEIGHT_MEASUREMENT.equals(characteristic.getUuid())) {
        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());

    } else {
        // For all other profiles, writes the data formatted in HEX.

        }
    }
    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_WEIGHT_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();
}
}

它工作正常，我得到了十六进制数据。

但是，我正在实施的一些事情非常困难。

• 如何获取十六进制值的第 5 位和第 6 位并将其转换为十进制以进行输出？
• 如何做到不用点击服务和特征来输出数据？ （我已经知道 UUID 的所以不需要点击）一旦我从扫描仪点击 BLE 设备，我希望它只显示重量数据。我尝试为此编写自己的代码，但尝试时似乎无法让通知正常工作。

非常感谢。

Answer 1

你可以有一个看起来像这样的方法。 试试这个：

  public static int asInt(@NonNull byte[] bytes) {
    checkArgument(bytes.length <= 4, "There must be at most 4 bytes to     transform to integer, got [%s].", bytes.length);

switch (bytes.length) {
  case 1:
    return (bytes[0] & 0xFF);
  case 2:
    return (bytes[0] & 0xFF) << 8 | (bytes[1] & 0xFF);
  case 3:
    return (bytes[0] & 0xFF) << 16 | (bytes[1] & 0xFF) << 8 | bytes[2] & 0xFF;
  case 4:
    return (bytes[0] & 0xFF) << 24 | (bytes[1] & 0xFF) << 16 | (bytes[2] & 0xFF) << 8 | bytes[3] & 0xFF;
}

throw new IllegalArgumentException(); }    

那你就可以这样解析了

byte[] extractWeightBytes(byte[] rawWeight) {
return new byte{ rawWeight[5] , rawWeight[6] }
}


int parseWeight(byte[] rawWeight) {
return asInt(extractWeightBytes(rawWeight));
}

我忘记了十六进制方法的字节：

  private static final char[] HEXADECIMAL_CHARACTERS = "0123456789ABCDEF".toCharArray();

  public static String bytesToHex(byte[] bytes) {
char[] characters = new char[bytes.length * 2];
for (int j = 0; j < bytes.length; j++) {
  int valueAsInt = bytes[j] & 0xFF;

  characters[j * 2] = HEXADECIMAL_CHARACTERS[valueAsInt >>> 4];
  characters[j * 2 + 1] = HEXADECIMAL_CHARACTERS[valueAsInt & 0x0F];
}

return new String(characters);
}

如果你不使用 Guava，你可以删除 checkArgument，它只是为了安全措施。其他有用的方法是来自 Guava 的 Ints 和 Bytes。