Setelah terhubung ke server BLE GATT, Anda dapat menggunakan koneksi untuk mencari tahu layanan apa yang tersedia di perangkat, membuat kueri data dari perangkat, dan meminta notifikasi saat karakteristik GATT tertentu berubah.
Menemukan layanan
Hal pertama yang harus dilakukan setelah Anda terhubung ke Server GATT pada perangkat BLE adalah melakukan penemuan layanan. Tindakan ini memberikan informasi tentang layanan
yang tersedia di perangkat jarak jauh, serta karakteristik layanan dan
deskriptornya. Pada contoh berikut, setelah layanan berhasil terhubung ke
perangkat (ditunjukkan oleh panggilan yang sesuai ke
fungsi onConnectionStateChange()
dari
BluetoothGattCallback
),
fungsi
discoverServices()
akan mengkueri informasi dari perangkat BLE.
Layanan perlu mengganti
fungsi onServicesDiscovered()
di
BluetoothGattCallback
.
Fungsi ini dipanggil saat perangkat melaporkan layanan yang tersedia.
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); } } }; }
Layanan menggunakan siaran untuk memberi tahu
aktivitas. Setelah layanan ditemukan, layanan dapat memanggil
getServices()
untuk
mendapatkan data yang dilaporkan.
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(); } }
Aktivitas tersebut kemudian dapat memanggil fungsi ini saat menerima intent siaran, yang menunjukkan bahwa penemuan layanan telah selesai.
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()); } } }; }
Membaca karakteristik BLE
Setelah aplikasi Anda terhubung ke server GATT dan menemukan layanan, aplikasi tersebut dapat membaca dan menulis atribut, jika didukung. Misalnya, cuplikan berikut melakukan iterasi melalui layanan dan karakteristik server serta menampilkannya di UI:
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); } ... } ... }
Layanan GATT menyediakan daftar karakteristik yang dapat Anda baca dari
perangkat. Untuk membuat kueri data, panggil fungsi readCharacteristic()
di BluetoothGatt
yang meneruskan BluetoothGattCharacteristic
yang ingin Anda baca.
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); } }
Dalam contoh ini, layanan mengimplementasikan fungsi untuk memanggil
readCharacteristic()
.
Ini adalah panggilan asinkron. Hasilnya dikirim ke
fungsi
BluetoothGattCallback
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); } } }; }
Saat dipicu, callback tertentu akan memanggil metode helper
broadcastUpdate()
yang sesuai dan meneruskan tindakan. Perhatikan bahwa penguraian
data di bagian ini dilakukan sesuai dengan spesifikasi profil Pengukuran Detak Jantung
Bluetooth.
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); }
Menerima notifikasi GATT
Sudah umum bagi aplikasi BLE untuk meminta agar diberi tahu saat karakteristik tertentu
berubah pada perangkat. Dalam contoh berikut, layanan mengimplementasikan
fungsi untuk memanggil
metode
setCharacteristicNotification()
:
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); } } }
Setelah notifikasi diaktifkan untuk karakteristik, callback
onCharacteristicChanged()
akan dipicu jika karakteristik berubah pada perangkat jarak jauh:
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); } }; }