[IEEE]
To avoid unresponsiveness, a core part of mobile development is asynchronous programming. Android providesseveral async constructs that developers can use. However, developers can still use the inappropriate async constructs, which result in memory leaks, lost results, and wasted energy. Fortunately, refactoring tools can eliminate these problems by transforming async code to use the appropriate constructs. In this paper we conducted a formative study on a corpusof 611 widely-used Android apps to map the asynchronouslandscape of Android apps, understand how developers retrofit asynchrony, and learn about barriers encountered by developers. Based on this study, we designed, implemented, and evaluated ASYNCDROID, a refactoring tool which enables Android developers to transform existing improperly-used async constructs into correct constructs. Our empirical evaluation shows that ASYNCDROID is applicable, accurate, and saves developers effort. We submitted 45 refactoring patches, and developers consider that the refactorings are useful.