在Android中后台下载多个文件

Question

Basically I'm trying to make a little app for watching offline content. So there's a moment where the user selects to download the contents (and the app should download about 300 small files and images).

I'd like to show the user how does the process go if he enters the proper activity. Showing a list of all the files, telling what has been already downloaded, in progress or waiting for download.

My problem is that I really don't know what approach to take for achieve this. Since the download should last until finished I imagine the solution is an Service , but whats best? an IntentService, a Bound Service or an Standard Service calling a startService() for each download? And how can I keep my objects updated for displaying them later? should I use a database or objects in memory?

Thanks

Answer 1

I would suggest using AsyncTask class, it allows you to easily move time consuming code(like downloading files) to a different thread. This will keep your app responsive, while giving you the ability to update your UI in the process.

It's hard to be more specific without having more details about how exactly you want your app to behave. Are the downloads only going to happen when the app is running or in the background as well?

Answer 2

You could use Asynctask or implement a ExecutorService with custom policies and send to it the download threads.
You need to keep a reference to the AsyncTask or a Future object respectively inside of a collection if you want to give the oportunity to the user to stop downloads. Of course, you need to call startService each time you want to download a new file. Service onCreate only is called if service is not running and onStartCommand run each time you call startService. In onStartCommand you run a new thread for download a new file. You can bind service with an activity and each time that your downloadsActivity is created you show the state of downloads implementing a custom Adapter. Service only finishes when you call activity.stopService or service.stopSelf