Subscribing to Notifications from the Gatt Server

You can request to be notified from the Gatt Server when the value of a characteristic has been changed:

gatt.setCharacteristicNotification(characteristic, true);
BluetoothGattDescriptor descriptor = characteristic.getDescriptor(
   UUID.fromString("00002902-0000-1000-8000-00805f9b34fb");
descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
mBluetoothGatt.writeDescriptor(descriptor);

All notifications from the server will be received in the onCharacteristicChanged method of your BluetoothGattCallback:

@Override
public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
super.onCharacteristicChanged(gatt, characteristic);
byte[] newValue = characteristic.getValue();
}

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