Android SyncAdapter Callback

Question

I have implemented a SyncAdapter, AccountManager and private ContentProvider along the lines of the SimpleSyncAdapter sample project in the SDK. It is all working well.

Now I want to show a message to the user when new rows have been downloaded from the remote server that have a specific flag set. I need a callback from the SyncAdapter when a Sync has finished so I can do the query and display the message from an activity. I have seen a few questions on StackOverflow discussing this but none with a good answer.

How does one listen for progress from Android SyncAdapter? says that the SyncStatusObserver is useless. User mobibob suggests using a ResultReceiver to respond back to the UI from the sync thread.

How to know when sync is finished? suggests using an Intent in your SyncService.

How to signal sync-complete to the Android SyncManager? suggests using the SyncResult. The example code linked to by maxpower47 uses the SyncResult class to report exceptions but not to actually report if a sync was successfully completed.

I just don't know which is the best option and I have not seen any example projects where any of these solutions are used.

Answer 1

I know this is an old question, but I was asking the same thing myself. What I found out as a good solution, specially because I'm dealing with local data as you are, is to use the following method from ContentResolver:

registerContentObserver(Uri uri, boolean notifyForDescendents, ContentObserver observer)

This register an observer class that get callback when data identified by a given content URI changes. But that can only happens if your ContentProvider send the notification. So for example, if you want to get notified on the ContentObserver above for all updates done on your database through a ContentProvider, your ContentProvider should implement update similar to this:

@Override
public int update(Uri uri, ContentValues contentValues, String s, String[] strings) {
    // code goes here
    this.getContext().getContentResolver().notifyChange(uri, null);
    return 0;
}

Using notifyForDescendents when you do a registerContentObserver can be very useful.