public override void OnAttach(Context context)
        {
            base.OnAttach(context);

            if (context is IBaseExampleFragmentCallbacks)
            {
                callbacks = (IBaseExampleFragmentCallbacks)context;
            }
            else
            {
                throw new Exception(context.GetType().FullName + " must implement IBaseExampleFragmentCallbacks.");
            }
        }
        public override void OnDetach()
        {
            base.OnDetach();

            callbacks = null;
        }