Understanding and detecting evolution-induced compatibility issues in Android apps

The frequent release of Android OS and its various versions bring many compatibility issues to Android Apps. This paper studies and addresses such evolution-induced compatibility problems. We conduct an extensive empirical study over 11 different Android versions and 4,936 Android Apps. Our study shows that there are drastic API changes between adjacent Android versions, with averagely 140.8 new types, 1,505.6 new methods, and 979.2 new fields being introduced in each release. However, the Android Support Library (provided by the Android OS) only supports less than 23% of the newly added methods, with much less support for new types and fields. As a result, 91.84% of Android Apps write additional code to support different OS versions. Furthermore, 88.65% of the supporting codes share a common pattern, which directly compares variable android.os.Build.VERSION.SDK_INT with a constant version number, to use an API of particular versions. Based on our findings, we develop a new tool called IctApiFinder, to detect incompatible API usages in Android applications. IctApiFinder effectively computes the OS versions on which an API may be invoked, using an inter-procedural data-flow analysis framework. It detects numerous incompatible API usages in 361 out of 1,425 Apps. Compared to Android Lint, IctApiFinder is sound and able to reduce the false positives by 82.1%. We have reported the issues to 13 Apps developers. At present, 5 of them have already been confirmed by the original developers and 3 of them have already been fixed.