Since the year 2000, the use of mobile applications in general and, more specifically, context-aware applications, becomes very popular in the contemporary and even future services. Indeed, in the field of online sales, we have Amazon application; in the banking field we have e-banking applications; in the field of health we have intelligent medical applications, HealthCare application; in the field of public services, we have e-government applications. The fundamental characteristic of these

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... plications is their ability to adapt or to react according to the information of the context. Quality of Services (QoS) and violation of Service Level Agreement (SLA) during adaptation activity are still a challenge that many researches try to address. Before addressing these problems of violation of SLA, it is important to present a concrete research work on implementing adaptation methods to better understand the adaptation activity concept. This concrete work can help companies to address adaptation issues, and better understand integration of OSGi adaptation technics on android system. In addition, the definition of an SLA between application providers and consumers to improve the QoS for application context-aware, is not obvious. This paper proposes a mechanism for addressing these issues, using existing adaptation works for the android platform, an architecture QoS pattern to preserve the quality service levels of the context-aware applications, design pattern observer and aspect oriented programming to realize service adjustment. This QoS pattern can help to guarantee the expected quality of services at runtime for contextual applications. More details of Design QoS Pattern for context-aware application will be given in the future work.