Android Fundamentals: Downloading Data With Services

The tutorial content of the still-unnamed “TutList” application we’ve been building together is getting stale. The data has been the same for over a month now. It’s time to breathe some life into the application by providing it with a means to read fresh Mobiletuts tutorial data on the fly.

As it stands now, our application reads a list of tutorial titles and links from a database. This is, fundamentally, the correct way to design the app. However, we need to add a component that retrieves new content from the Mobiletuts website and stores new titles and links in the application database. This component will download the raw RSS feed from the site, parse it for the title and link, then store that data into the database. The database will be modified to disallow duplicate links. Finally, a refresh option will be placed within the list fragment so the user can manually force an update of the database.

As with other tutorials in this series, the pacing will be faster than some of our beginner tutorials; you may have to review some of the other Android tutorials on this site or even in the Android SDK reference if you are unfamiliar with any of the basic Android concepts and classes discussed in this tutorial. The final sample code that accompanies this tutorial is available for download as open-source from the Google code hosting.

Step 0: Getting Started

This tutorial assumes you will start where our last tutorial, Android Fundamentals: Properly Loading Data, left off. You can download that code and work from there or you can download the code for this tutorial and follow along. Either way, get ready by downloading one or the other project and importing it into Eclipse.

Step 1: Creating the Service Class

One way to handle background processing, such as downloading and parsing the Mobiletuts tutorial feed, is to implement an Android service for this purpose. The service allows you to componentize the downloading task from any particular activity or fragment. Later on, this will allow it to easily perform the operation without the activity launching at all.

So let’s create the service. Begin by creating a new package, just like the data package. We named ours com.mamlambo.tutorial.tutlist.service. Within this package, add a new class called TutListDownloaderService and have it extend the Service class (android.app.Service). Since a service does not actually run in a new thread or process from the host (whatever other process or task starts it, in this case, an Activity), we need to also create a class to ensure that the background work is done asyncronously. For this purpose, we could use a Thread/Handler design or simply use the built-in AsyncTask class provided with the Android SDK to simplify this task.

Read more: MobileTuts

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