Android BLE onCharacteristicChanged未调用

Question

I'm working on a project which includes a Bluegiga BLE113 module and an Android app. On the Bluegiga module I've set up several characteristics. For one characteristic I defined a descriptor to activate the client notification (in My case, the client is the Android app.). The characteristic definition of the BLE113 module looks like this:

:
<characteristic uuid="dcfa2671-974d-4e4a-96cd-6221afeabb62" id="ez1_flow_data_out">
  <!-- org.bluetooth.descriptor.gatt.characteristic_user_description -->
  <description>Data to transmit to Android device</description>
  <properties write="true" read="true" />
  <value variable_length="true" length="255" type="hex" />
  <!-- org.bluetooth.descriptor.gatt.client_characteristic_configuration -->
  <descriptor uuid="2902">
    <properties write="true" read="true" const="false" />
    <!-- Bit 0 = 1: Notifications enabled -->
    <value type="hex">0001</value>
    </descriptor>
:
:
</characteristic>

On the Android side I've set up the notification inside the onServicesDiscovered(...) callback according to the Android Bluetooth Low Energy guide:

characteristic = gatt.getService(BLEuuids.DATAFLOW_SERVICE).getCharacteristic(BLEuuids.DATAFLOW_OUT_CHARACT);
//Enable local notifications
gatt.setCharacteristicNotification(characteristic, true);
//Enabled remote notifications
BluetoothGattDescriptor desc = characteristic.getDescriptor(BLEuuids.DATAFLOW_OUT_DESCRIPT);
boolean test;
test = desc.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);  // return value = true
test = gatt.readDescriptor(desc);  // return value = true
test = gatt.writeDescriptor(desc);  // return value = true

However, if I change the Value of the DATAFLOW_OUT_CHARACT characteristics UUID, using the serial interface of the Bluegiga Module, the intended callback onCharacteristicChanged(...) isn't triggered on My Android app.

Answer 1

Try not to READ descriptor. Do write descriptor right after set. Properly the read will overwrite your set and you write the same value back?