Android - Looper that quits keeps open files/pipes

Question

I noticed that whenever a thread that runs with a Looper object is finished (i.e. Looper.quit() is called), some files remain open (3 files usually). You can see that by running "adb shell ls /proc//fd | wc -l"

This happens because the MessageQueue inside Looper is never freed, although it's never used. Only if I call the finalize() method on the MessageQueue, then these files are freed. The files may remain open hours after the thread is finished.
This causes a problem when these threads run in system process because there are many open files already, and I can't exceed the 1024 file boundary. (BTW even when I call System.gc() it doesn't finalize MessageQueue)

Is there anyway (without using reflection) to have MessageQueue finalize method invoked? It seems to me like a bug in Android that the GC doesn't do it by itself even when the number of open files is big.

Answer 1

GC doesn't clear staled objects if you have some references to them. Good explanations is here: http://dubroy.com/blog/google-io-memory-management-for-android-apps/

Answer 2

Speaking very generally, never quit() your looper threads. That method exists mostly for historical and testing reasons. In Real Life™, I recommend that you continue to reuse the same looper thread(s) for the life of the process rather than creating/quitting them.