Retrive eventData

I have a problem understanding how sending eventProps works.

I raise a event with custom data
HashMap<Object, Object> eventProps = new HashMap<Object, Object>();
eventProps.put((byte)21, "some data");
this.loadBalancingPeer.opRaiseEvent((byte)1, eventProps, false, (byte) 0);

Now i want to read the data in th onEvent method
switch (eventData.Code) {
case 1:
// eventData.Parameters.get((byte)21) get a null pointer exception
// eventData.get((byte)21) get a null pointer exception


any explanation of how to send and read customEvent Props correctly would be appreciated :)

I am using version of the Android sdk with photon cloud