 on some I/O operation
(frequently a network access) on the UI thread so the system can't
process incoming user input events. Or perhaps the app
spends too much time building an elaborate in-memory
structure or computing the next move in a game on the UI thread. It's always important to make
sure these computations are efficient, but even the
most efficient code still takes time to run.</p>

<p>In any situation in which your app performs a potentially lengthy operation,
<strong>you should not perform the wo