System Introspection for System Analysis on Mobile Devices

Figure 4.2: The different layer of BonSAI - The top layer containselements <strong>for</strong> complex behaviors, the middle layerholds functional components <strong>for</strong> base tasks and the bottomlayer controls low level hardware components [FromWachsmuth et al. (2011)]Open Handset Alliance 8 . The architecture behind Android provides an operatingsystem, middle-ware and several key applications placed in differentlayers (Figure 4.3). Android applications can be written with the Java programminglanguage through the Android SDK 9 . Android comes with support<strong>for</strong> wireless connections (Bluetooth, WIFI, EDGE, 3G), hardware components(cameras, GPS, accelerometer) and media support. Android relies on a Linuxkernel which acts as abstraction layer between hardware and software.Android offers an open development plat<strong>for</strong>m to allow developers the creationof rich and innovative applications. Each Android applications runs withinits own life cycle (Figure 4.4) and is called activity. An activity consists ofa class containing the logic and an XML file describing the layout of the activity.The life cycle describes the different states of an activity presented bydifferent methods. The onCreate()-method is called once an activity startsand initializes the components. The onStart()-method is triggered when allconfiguration of the creation state has ended. Once started the activity runsin the <strong>for</strong>eground of the device within the onResume()-method. In this methodthe interaction with the user takes place. If the user stops the activity it is notdirectly destroyed. The state of the activity is changed to onPause() and thenonStop(). In this state the operation system places the activity in the background.If the activity is requested again the onRestart()-method is called. Ifthe activity has been terminated by the operation system due to the need ofresources the onCreate()-method is called if the activity is requested. If theactivities interaction is finally finished the onDestroy()-method is called andthe activity ends. One application can contain several activities to provide interactionwith the user. The operating system there<strong>for</strong>e decides which activityis running in <strong>for</strong>eground and sends unused activities to the background.8 http://www.webcitation.org/5wiFwDWLg - Open Handset Alliance9 http://www.webcitation.org/5wrOKYh2w - Android Developer Guide15