Launching mutliple threads inside an IntentService

Question

What I want to do sounds pretty simple in theory - I need to scan all the MP3 files present in the device, and perform some metadata updates by querying something like AcoustId or GraceNote.

I'm planning on using a class by extending IntentService, and in the onHandleIntent(), I plan on creating N threads, each thread updating the metadata of a single file. The main reason for me using IntentServices is that I need no communication with the UI thread, and that the task at hand is relatively time consuming.

My main question is this: Will the IntentService support custom threads? If not, what is my best alternative? I know I shouldn't be using AsyncTasks, as they're used only for relatively small computations.

Thanks in advance!

Answer 1

No, an IntentService only has a single worker thread, handling incoming Intents sequentially. You should just extend Service if you want to do something more complicated.

Answer 2

Spawning N threads never sounds like a great idea, especially when list of your tasks is unbound (who knows how many mp3 tracks have you got)

One of the conveniences you can use is Android's threadpool that will give you level of parallelism but also some sane boundaries

Note that AsyncTask is not intended for smth that need to run for minutes or hours but one or two http queries can totally make it in recommended 'few seconds' timeframe

What matters the most though is that all operations you have described are I/O and don't need extra threads at all if you have access to async I/O api, all your threads would just be waiting for network or filesystem access, so wasteful. If you can afford using (and learning) AsynchronousFileChannel and AsyncHttpClient it could make big difference in terms of quality and scalability for your app