The \emph{executes-before} relation between tasks is fundamental in
the analysis of Event Driven Programs with several downstream
applications like race detection and identifying redundant
synchronizations.
We present a sound, efficient, and effective static analysis technique
to compute executes-before pairs of tasks for a general class of event
driven programs.
The analysis is based on a small but comprehensive set of rules
evaluated on a novel structure called the \emph{task post graph} of a
program.
We show how to use the executes-before information to identify
disjoint-blocks in event driven programs and further use them to improve the
precision of data race detection for these programs.
We have implemented our analysis in the Flowdroid
framework in a tool called \textsc{AndRacer} and evaluated it on several
Android apps, bringing out the scalability, recall, and improved
precision of the analyses