Reading battery level from bluetooth A2DP devices Android

Question

I'm trying to read battery level of my bluetooth headphones(Skullcandy Method Wireless). So far, i'm successful in receiving connectivity broadcast when headphones are connected, connect to GATT via bluetoothDevice.connectGatt().

//getting device
  BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);

On BluetoothGattCallback.onConnectionChanged, i'm calling discoverServices() to discover bluetooth Battery_Service. But the list of services is always zero.

BluetoothGatt bluetoothGatt = device.connectGatt(context, false, new BluetoothGattCallback() {

            @Override
            public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
                super.onConnectionStateChange(gatt, status, newState);
                Logger.log(A2dpConnectionStateReceiver.class, "onConnectionStateChange "+newState);
                if(newState == BluetoothProfile.STATE_CONNECTED) {
                    Logger.log(A2dpConnectionStateReceiver.class, "onConnectionStateChange state connected, triggering discover services " + gatt.discoverServices());
                }
            }

            @Override
            public void onServicesDiscovered(BluetoothGatt gatt, int status) {
                super.onServicesDiscovered(gatt, status);
                Logger.log(A2dpConnectionStateReceiver.class, "onServicesDiscovered count = "+gatt.getServices().size()+" status="+ (status == BluetoothGatt.GATT_SUCCESS? "success" : "failed") );

            }

            @Override
            public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
                super.onCharacteristicChanged(gatt, characteristic);
                Logger.log(A2dpConnectionStateReceiver.class, "onCharacteristicChanged "+characteristic.getUuid());
                if(characteristic.getUuid().equals(Battery_Level_UUID)) {
                    Logger.log(A2dpConnectionStateReceiver.class, "onCharacteristicChanged battery level at "+characteristic.getIntValue(BluetoothGattCharacteristic.FORMAT_UINT8, 0));
                }
            }
        });