title: Android BLE API: GATT Notification not received
body: <p>Device used for testing: Nexus 4, Android 4.3</p>
  
  <p>Connection is working fine but the <code>onCharacteristicChanged</code>Method of my callback is never called. However I am registering for notifications using <code>setCharacteristicNotification(char, true)</code> inside <code>onServicesDiscovered</code> and that function even returns true.</p>
  
  <p>Device log (there are actually <em>no</em> messages at all when notifications <em>should</em> appear / are sent via the Bluetooth device):</p>
  
  <pre><code>07-28 18:15:06.936  16777-16809/de.ffuf.leica.sketch D/BluetoothGatt: setCharacteristicNotification() - uuid: 3ab10101-f831-4395-b29d-570977d5bf94 enable: true
  07-28 18:15:06.936    4372-7645/com.android.bluetooth D/BtGatt.GattService: registerForNotification() - address=C9:79:25:34:19:6C enable: true
  07-28 18:15:06.936    4372-7645/com.android.bluetooth D/BtGatt.btif: btif_gattc_reg_for_notification
  07-28 18:15:06.946    4372-7645/com.android.bluetooth D/BtGatt.btif: btgattc_handle_event: Event 1018
  07-28 18:15:06.946    4372-7645/com.android.bluetooth D/BtGatt.GattService: onRegisterForNotifications() - address=null, status=0, registered=1, charUuid=3ab10101-f831-4395-b29d-570977d5bf94
  07-28 18:15:06.946    4372-7645/com.android.bluetooth D/BtGatt.btif: btgattc_handle_event: Event 1016
  07-28 18:15:06.946    4372-7645/com.android.bluetooth D/BtGatt.btif: btgattc_handle_event: Event 1018
  07-28 18:15:06.946    4372-7645/com.android.bluetooth D/BtGatt.GattService: onRegisterForNotifications() - address=null, status=0, registered=1, charUuid=3ab10102-f831-4395-b29d-570977d5bf94
  07-28 18:15:06.946    4372-7645/com.android.bluetooth D/BtGatt.btif: btgattc_handle_event: Event 1016
  07-28 18:15:06.946    4372-7684/com.android.bluetooth E/bt-btif: already has a pending command!!
  07-28 18:15:06.946    4372-7645/com.android.bluetooth D/BtGatt.btif: btgattc_handle_event: Event 1013
  07-28 18:15:06.946    4372-7684/com.android.bluetooth E/bt-btif: already has a pending command!!
  07-28 18:15:06.946    4372-7645/com.android.bluetooth D/BtGatt.btif: btgattc_handle_event: Event 1013
  07-28 18:15:06.946    4372-7684/com.android.bluetooth E/bt-btif: already has a pending command!!
  07-28 18:15:06.976    4372-7645/com.android.bluetooth D/BtGatt.btif: btif_gattc_upstreams_evt: Event 9
  </code></pre>
  
  <p>GATT Notifications work fine using iOS and the app basically does the same as on Android (registering for notification etc.).</p>
  
  <p>Has anyone else experienced this with a possible solution?</p>