Computing devices and applications are now used beyond the desktop, in diverse environments, and this trend toward ubiquitous computing is evolving. In this study, we re-visit the interactivity concept and its applications for interactive function design in a ubiquitous-learning system (ULS). Further, we compare interactivity dimensions and corresponding interactive functions of web-based learning systems with ULS, and we offer a technical framework for a successful incorporation of interactive functions into ULS. To enhance the ease-of-use and the overall effectiveness of this framework, each of the four panels of experts assessed its own interactive-function term: learning needs, instructional necessity, mobile-interface design, or programming difficulty. Last, this study presents the best practices of a learner-centered ULS and discusses the panel experts' reviews of interactive functions in such a learning environment, along with suggestions for future research. (Contains 2 figures and 10 tables.)