Une fois que vous êtes connecté à un GATT BLE, Google Cloud, vous pouvez utiliser la connexion pour savoir quels services sont disponibles sur l'appareil, interroger des données de l'appareil, et demander des notifications lorsqu'une certaine caractéristique GATT des modifications.
Découvrir les services
Une fois connecté au serveur GATT sur l'appareil BLE, la première chose à faire est
pour effectuer une détection de services. Cela fournit des informations sur les services
disponibles sur l'appareil distant, ainsi que les caractéristiques du service et leurs
de descripteurs. Dans l'exemple suivant, une fois que le service se connecte
l'appareil (indiqué par l'appel approprié à la
onConnectionStateChange()
de la fonction
BluetoothGattCallback),
la
discoverServices()
interroge les informations de l’appareil BLE.
Le service doit remplacer
onServicesDiscovered()
de la fonction
BluetoothGattCallback
Cette fonction est appelée lorsque l'appareil signale les services disponibles.
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);
}
}
};
}
Le service utilise des annonces pour avertir le
activité. Une fois les services découverts, ils peuvent appeler
getServices() jusqu'à
obtenir les données du rapport.
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();
}
}
L'activité peut ensuite appeler cette fonction lorsqu'elle reçoit l'intent de diffusion. indiquant que la détection de services est terminée.
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());
}
}
};
}
Lire les caractéristiques BLE
Une fois que votre application s'est connectée à un serveur GATT et a détecté des services, elle peut lire et écrire des attributs, s'ils sont compatibles. Par exemple : l'extrait de code parcourt les services et les caractéristiques du serveur, puis affiche dans l'interface utilisateur:
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);
}
...
}
...
}
Le service GATT fournit une liste de caractéristiques que vous pouvez lire à partir des
appareil. Pour interroger les données, appelez la méthode
readCharacteristic()
sur la
BluetoothGatt, en transmettant
BluetoothGattCharacteristic
que vous voulez lire.
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);
}
}
Dans cet exemple, le service implémente une fonction pour appeler
readCharacteristic()
Il s'agit d'un appel asynchrone. Les résultats sont envoyés
BluetoothGattCallback
fonction
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);
}
}
};
}
Lorsqu'un rappel particulier est déclenché, il appelle la méthode
broadcastUpdate() et lui transmet une action. Notez que les données
de cette section est effectuée conformément aux règles relatives à la fréquence cardiaque
Spécifications du profil de mesure.
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);
}
Recevoir des notifications GATT
Il est courant que les applications BLE demandent à être averties lorsqu'une caractéristique particulière
sur l'appareil. Dans l'exemple suivant, le service implémente un
pour appeler la fonction
setCharacteristicNotification()
méthode:
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);
}
}
}
Une fois les notifications activées pour une caractéristique, une
onCharacteristicChanged()
est déclenché si la caractéristique change sur l'appareil distant:
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);
}
};
}