传输 BLE 数据

连接到 BLE GATT 后， 服务器，您可以使用 以了解设备上提供哪些服务、查询数据 ，并在特定 GATT 特征时请求通知 更改。

发现服务

在 BLE 设备上连接到 GATT 服务器后，首先要做的是 来执行服务发现。此信息可提供有关您所用服务 以及服务特征及其 描述符。在以下示例中，服务成功连接到 设备（通过对 onConnectionStateChange() 的 BluetoothGattCallback), 该 discoverServices() 函数从 BLE 设备中查询信息。

该服务需要覆盖 onServicesDiscovered() 函数 BluetoothGattCallback。 此函数在设备报告其可用服务时被调用。

Kotlin

class BluetoothLeService : Service() {

...

private val bluetoothGattCallback = object : BluetoothGattCallback() {
    override fun onConnectionStateChange(gatt: BluetoothGatt?, status: Int, newState: Int) {
        if (newState == BluetoothProfile.STATE_CONNECTED) {
            // successfully connected to the GATT Server
            broadcastUpdate(ACTION_GATT_CONNECTED)
            connectionState = STATE_CONNECTED
            // Attempts to discover services after successful connection.
            bluetoothGatt?.discoverServices()
        } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
            // disconnected from the GATT Server
            broadcastUpdate(ACTION_GATT_DISCONNECTED)
            connectionState = STATE_DISCONNECTED
        }
    }

    override fun onServicesDiscovered(gatt: BluetoothGatt?, status: Int) {
        if (status == BluetoothGatt.GATT_SUCCESS) {
            broadcastUpdate(ACTION_GATT_SERVICES_DISCOVERED)
        } else {
            Log.w(BluetoothLeService.TAG, "onServicesDiscovered received: $status")
        }
    }
}

...

companion object {
  const val ACTION_GATT_CONNECTED = "com.example.bluetooth.le.ACTION_GATT_CONNECTED"
  const val ACTION_GATT_DISCONNECTED =
              "com.example.bluetooth.le.ACTION_GATT_DISCONNECTED"
  const val ACTION_GATT_SERVICES_DISCOVERED =
              "com.example.bluetooth.le.ACTION_GATT_SERVICES_DISCOVERED"

  private const val STATE_DISCONNECTED = 0
  private const val STATE_CONNECTED = 2
}

Java

class BluetoothLeService extends Service {

    public final static String ACTION_GATT_SERVICES_DISCOVERED =
            "com.example.bluetooth.le.ACTION_GATT_SERVICES_DISCOVERED";

    ...

    private final BluetoothGattCallback bluetoothGattCallback = new BluetoothGattCallback() {
        @Override
        public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
            if (newState == BluetoothProfile.STATE_CONNECTED) {
                // successfully connected to the GATT Server
                connectionState = STATE_CONNECTED;
                broadcastUpdate(ACTION_GATT_CONNECTED);
                // Attempts to discover services after successful connection.
                bluetoothGatt.discoverServices();
            } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
                // disconnected from the GATT Server
                connectionState = STATE_DISCONNECTED;
                broadcastUpdate(ACTION_GATT_DISCONNECTED);
            }
        }

        @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);
            }
        }
    };
}

该服务使用广播来通知 活动。发现服务后，服务便可调用 getServices()至 获取报告的数据。

Kotlin

class BluetoothLeService : Service() {

...

  fun getSupportedGattServices(): List<BluetoothGattService?>? {
      return bluetoothGatt?.services
  }
}

Java

class BluetoothLeService extends Service {

...

    public List<BluetoothGattService> getSupportedGattServices() {
        if (bluetoothGatt == null) return null;
        return bluetoothGatt.getServices();
    }
}

然后，activity 在收到广播 intent 时可以调用此函数， 表示服务发现已完成。

Kotlin

class DeviceControlActivity : AppCompatActivity() {

...

    private val gattUpdateReceiver: BroadcastReceiver = object : BroadcastReceiver() {
        override fun onReceive(context: Context, intent: Intent) {
            when (intent.action) {
                BluetoothLeService.ACTION_GATT_CONNECTED -> {
                    connected = true
                    updateConnectionState(R.string.connected)
                }
                BluetoothLeService.ACTION_GATT_DISCONNECTED -> {
                    connected = false
                    updateConnectionState(R.string.disconnected)
                        }
                BluetoothLeService.ACTION_GATT_SERVICES_DISCOVERED -> {
                    // Show all the supported services and characteristics on the user interface.
                    displayGattServices(bluetoothService?.getSupportedGattServices())
                }
            }
        }
    }
}

Java

class DeviceControlsActivity extends AppCompatActivity {

...

    private final BroadcastReceiver gattUpdateReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            final String action = intent.getAction();
            if (BluetoothLeService.ACTION_GATT_CONNECTED.equals(action)) {
                connected = true;
                updateConnectionState(R.string.connected);
            } else if (BluetoothLeService.ACTION_GATT_DISCONNECTED.equals(action)) {
                connected = false;
                updateConnectionState(R.string.disconnected);
            } else if (BluetoothLeService.ACTION_GATT_SERVICES_DISCOVERED.equals(action)) {
                // Show all the supported services and characteristics on the user interface.
                displayGattServices(bluetoothService.getSupportedGattServices());
            }
        }
    };
}

读取 BLE 特性

一旦您的应用连接到 GATT 服务器并发现服务， 可以读取和写入属性（在支持的情况下）。例如，以下 该代码段会循环访问服务器的服务和特征，并显示 在界面中执行以下操作：

Kotlin

class DeviceControlActivity : Activity() {

    // Demonstrates how to iterate through the supported GATT
    // Services/Characteristics.
    // In this sample, we populate the data structure that is bound to the
    // ExpandableListView on the UI.
    private fun displayGattServices(gattServices: List<BluetoothGattService>?) {
        if (gattServices == null) return
        var uuid: String?
        val unknownServiceString: String = resources.getString(R.string.unknown_service)
        val unknownCharaString: String = resources.getString(R.string.unknown_characteristic)
        val gattServiceData: MutableList<HashMap<String, String>> = mutableListOf()
        val gattCharacteristicData: MutableList<ArrayList<HashMap<String, String>>> =
                mutableListOf()
        mGattCharacteristics = mutableListOf()

        // Loops through available GATT Services.
        gattServices.forEach { gattService ->
            val currentServiceData = HashMap<String, String>()
            uuid = gattService.uuid.toString()
            currentServiceData[LIST_NAME] = SampleGattAttributes.lookup(uuid, unknownServiceString)
            currentServiceData[LIST_UUID] = uuid
            gattServiceData += currentServiceData

            val gattCharacteristicGroupData: ArrayList<HashMap<String, String>> = arrayListOf()
            val gattCharacteristics = gattService.characteristics
            val charas: MutableList<BluetoothGattCharacteristic> = mutableListOf()

            // Loops through available Characteristics.
            gattCharacteristics.forEach { gattCharacteristic ->
                charas += gattCharacteristic
                val currentCharaData: HashMap<String, String> = hashMapOf()
                uuid = gattCharacteristic.uuid.toString()
                currentCharaData[LIST_NAME] = SampleGattAttributes.lookup(uuid, unknownCharaString)
                currentCharaData[LIST_UUID] = uuid
                gattCharacteristicGroupData += currentCharaData
            }
            mGattCharacteristics += charas
            gattCharacteristicData += gattCharacteristicGroupData
        }
    }
}

Java

public class DeviceControlActivity extends Activity {
    ...
    // Demonstrates how to iterate through the supported GATT
    // Services/Characteristics.
    // In this sample, we populate the data structure that is bound to the
    // ExpandableListView on the UI.
    private void displayGattServices(List<BluetoothGattService> gattServices) {
        if (gattServices == null) return;
        String uuid = null;
        String unknownServiceString = getResources().
                getString(R.string.unknown_service);
        String unknownCharaString = getResources().
                getString(R.string.unknown_characteristic);
        ArrayList<HashMap<String, String>> gattServiceData =
                new ArrayList<HashMap<String, String>>();
        ArrayList<ArrayList<HashMap<String, String>>> gattCharacteristicData
                = new ArrayList<ArrayList<HashMap<String, String>>>();
        mGattCharacteristics =
                new ArrayList<ArrayList<BluetoothGattCharacteristic>>();

        // Loops through available GATT Services.
        for (BluetoothGattService gattService : gattServices) {
            HashMap<String, String> currentServiceData =
                    new HashMap<String, String>();
            uuid = gattService.getUuid().toString();
            currentServiceData.put(
                    LIST_NAME, SampleGattAttributes.
                            lookup(uuid, unknownServiceString));
            currentServiceData.put(LIST_UUID, uuid);
            gattServiceData.add(currentServiceData);

            ArrayList<HashMap<String, String>> gattCharacteristicGroupData =
                    new ArrayList<HashMap<String, String>>();
            List<BluetoothGattCharacteristic> gattCharacteristics =
                    gattService.getCharacteristics();
            ArrayList<BluetoothGattCharacteristic> charas =
                    new ArrayList<BluetoothGattCharacteristic>();
           // Loops through available Characteristics.
            for (BluetoothGattCharacteristic gattCharacteristic :
                    gattCharacteristics) {
                charas.add(gattCharacteristic);
                HashMap<String, String> currentCharaData =
                        new HashMap<String, String>();
                uuid = gattCharacteristic.getUuid().toString();
                currentCharaData.put(
                        LIST_NAME, SampleGattAttributes.lookup(uuid,
                                unknownCharaString));
                currentCharaData.put(LIST_UUID, uuid);
                gattCharacteristicGroupData.add(currentCharaData);
            }
            mGattCharacteristics.add(charas);
            gattCharacteristicData.add(gattCharacteristicGroupData);
         }
    ...
    }
...
}

GATT 服务提供了一系列特征，您可以从 设备。要查询数据，请调用 readCharacteristic() 函数 BluetoothGatt，传入 BluetoothGattCharacteristic 想要阅读的内容

Kotlin

class BluetoothLeService : Service() {

...

    fun readCharacteristic(characteristic: BluetoothGattCharacteristic) {
        bluetoothGatt?.let { gatt ->
            gatt.readCharacteristic(characteristic)
        } ?: run {
            Log.w(TAG, "BluetoothGatt not initialized")
            Return
        }
    }
}

Java

class BluetoothLeService extends Service {

...

    public void readCharacteristic(BluetoothGattCharacteristic characteristic) {
        if (bluetoothGatt == null) {
            Log.w(TAG, "BluetoothGatt not initialized");
            return;
        }
        bluetoothGatt.readCharacteristic(characteristic);
    }
}

在此示例中，服务实现了一个用于调用 readCharacteristic()。 这是一个异步调用。系统会将结果发送到 BluetoothGattCallback 函数 onCharacteristicRead()。

Kotlin

class BluetoothLeService : Service() {

...

    private val bluetoothGattCallback = object : BluetoothGattCallback() {

        ...

        override fun onCharacteristicRead(
            gatt: BluetoothGatt,
            characteristic: BluetoothGattCharacteristic,
            status: Int
            ) {
                if (status == BluetoothGatt.GATT_SUCCESS) {
                broadcastUpdate(BluetoothLeService.ACTION_DATA_AVAILABLE, characteristic)
            }
        }
    }
}

Java

class BluetoothLeService extends Service {

...

    private final BluetoothGattCallback bluetoothGattCallback = new BluetoothGattCallback() {

    ...

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

当特定回调被触发时，它会调用相应的 broadcastUpdate() 辅助方法，并向其传递操作。请注意， 本部分根据蓝牙心率执行解析 测量配置文件规范。

Kotlin

private fun broadcastUpdate(action: String, characteristic: BluetoothGattCharacteristic) {
    val intent = Intent(action)

    // This is special handling for the Heart Rate Measurement profile. Data
    // parsing is carried out as per profile specifications.
    when (characteristic.uuid) {
        UUID_HEART_RATE_MEASUREMENT -> {
            val flag = characteristic.properties
            val format = when (flag and 0x01) {
                0x01 -> {
                    Log.d(TAG, "Heart rate format UINT16.")
                    BluetoothGattCharacteristic.FORMAT_UINT16
                }
                else -> {
                    Log.d(TAG, "Heart rate format UINT8.")
                    BluetoothGattCharacteristic.FORMAT_UINT8
                }
            }
            val heartRate = characteristic.getIntValue(format, 1)
            Log.d(TAG, String.format("Received heart rate: %d", heartRate))
            intent.putExtra(EXTRA_DATA, (heartRate).toString())
        }
        else -> {
            // For all other profiles, writes the data formatted in HEX.
            val data: ByteArray? = characteristic.value
            if (data?.isNotEmpty() == true) {
                val hexString: String = data.joinToString(separator = " ") {
                    String.format("%02X", it)
                }
                intent.putExtra(EXTRA_DATA, "$data\n$hexString")
            }
        }
    }
    sendBroadcast(intent)
}

Java

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.
    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);
}

接收 GATT 通知

当出现特定特征时，BLE 应用通常会要求接收通知 更改在以下示例中，服务将实现 函数来调用 setCharacteristicNotification() 方法：

Kotlin

class BluetoothLeService : Service() {

...

    fun setCharacteristicNotification(
    characteristic: BluetoothGattCharacteristic,
    enabled: Boolean
    ) {
        bluetoothGatt?.let { gatt ->
        gatt.setCharacteristicNotification(characteristic, enabled)

        // This is specific to Heart Rate Measurement.
        if (BluetoothLeService.UUID_HEART_RATE_MEASUREMENT == characteristic.uuid) {
            val descriptor = characteristic.getDescriptor(UUID.fromString(SampleGattAttributes.CLIENT_CHARACTERISTIC_CONFIG))
            descriptor.value = BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE
            gatt.writeDescriptor(descriptor)
        }
        } ?: run {
            Log.w(BluetoothLeService.TAG, "BluetoothGatt not initialized")
        }
    }
}

Java

class BluetoothLeService extends Service {

...

    public void setCharacteristicNotification(BluetoothGattCharacteristic characteristic,boolean enabled) {
        if (bluetoothGatt == null) {
            Log.w(TAG, "BluetoothGatt not initialized");
            Return;
        }
        bluetoothGatt.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);
            bluetoothGatt.writeDescriptor(descriptor);
        }
    }
}

为某个特征启用通知后， onCharacteristicChanged() 回调将触发回调函数：

Kotlin

class BluetoothLeService : Service() {

...

    private val bluetoothGattCallback = object : BluetoothGattCallback() {
        ...

        override fun onCharacteristicChanged(
        gatt: BluetoothGatt,
        characteristic: BluetoothGattCharacteristic
        ) {
            broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic)
        }
    }
}

Java

class BluetoothLeService extends Service {

...

    private final BluetoothGattCallback bluetoothGattCallback = new BluetoothGattCallback() {
    ...

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