convert AsyncTasks to IntentService

[yulin2]

Hi OpenTripPlanner-for-Android developers, I'm doing research on Android async programming, particularly on AsyncTask and IntentService. AsyncTask can lead to memory leak and losing task result when GUI is recreated during task running (such as orientation change). This article describes the problems very well.

We discussed with some Android experts and they agree with this issue, and claim that AsyncTask can be considered only for short tasks (less than 1 second). However, using IntentService (or AsyncTaskLoader) can avoid such problems since their lifecycles are independent from Activity/Fragment.

In OpenTripPlanner-for-Android, most of the AsyncTasks hold weak reference to an activity. It doesn't result in memory leak but may lead to wasting task result (when weak reference is GCed and points to null). Why not use IntentService instead, so that the BroadcastReceiver can hold a strong reference to activity while also avoid memory leak?

I refactored 3 AsyncTasks in OpenTripPlanner-for-Android to IntentService (in 3 commits), with the help of a refactoring tool we developed. Do you think using IntentService should be better in some of these 3 scenario? Do you want to merge (some) commits in this pr? Thanks.

[barbeau]

@yulin2 Thanks for this, I'll hopefully be able to review in the next few weeks.

I'm spending more time on another project these days - would you be able to run your refactoring tool on the develop branch of the below repo and open a PR there?

https://github.com/OneBusAway/onebusaway-android/tree/develop

I'd likely be able to review that sooner, and it may fit in with some other changes I plan to make there.

[yulin2]

Thanks for the reply! I tried to convert the AsyncTask ObaRegionsTask in OneBusAway to IntentService in pr #267.

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