How to notify activity about sync errors when using SyncAdapter

Question

I have a table called student which I want to populate from the server. In my activity I show a progress bar and call ContentProvder.requestSync(Content URI of student..). Now if I understand correctly as per Virgil's talk I should add an observer on the ContentURI of the student to be notified later by the ContentProvider when the sync finishes. But what happens if say there was a network error. The student table will never be populated and my progress dialog will never be removed. I understand the

"broadcast receiver approach"

mentioned in another thread but that deviates from Virgil's approach which I consider ideal. Also on those lines why doesn't the requestSync allow to pass a ResultReceiver as part of the extras. Isn't that generally a Service talks back to an Activity?

Answer 1

A SyncAdapter is not meant to be used for this kind of scenario. SyncAdapter is meant for background sync of data, invisible to the user.

Your case sounds like perfect for a AsyncTask. With that you can use publishProgress() to update your progress bar while your network task happens in another thread. You can find a lot of information and examples on AsyncTask online.

Example from the link above:

private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
     protected Long doInBackground(URL... urls) {
         int count = urls.length;
         long totalSize = 0;
         for (int i = 0; i < count; i++) {
             totalSize += Downloader.downloadFile(urls[i]);
             publishProgress((int) ((i / (float) count) * 100));
             // Escape early if cancel() is called
             if (isCancelled()) break;
         }
         return totalSize;
     }

     protected void onProgressUpdate(Integer... progress) {
         setProgressPercent(progress[0]);
     }

     protected void onPostExecute(Long result) {
         showDialog("Downloaded " + result + " bytes");
     }
 }

run it by executing it like so:

new DownloadFilesTask().execute(url1, url2, url3);

Here is another example, with tutorial (simply found by google):

http://androidresearch.wordpress.com/2012/03/17/understanding-asynctask-once-and-forever/