How to automatically re-query with LoaderManager

Question

I have an app that shows data from a SQLite DB and the data changes constantly, so obviously, I thought I should use a LoaderManager to show the data.

do I read a bit about using the LoaderManager with SQLite and saw Alex Lokwood's answer about implementing the CursorLoader and using it, and I saw the this answer about using a CursorLoader directly to an SQLite DB instead of a ContentProvider and started using commonsware's Loaderex.

I created this class for showing the data in a ListView:

public class LandingPageActivity extends FragmentActivity implements LoaderCallbacks<Cursor> {
    ListView list;
    SimpleCursorAdapter mAdapter;

    private SQLiteCursorLoader loader = null;
    private Context mContext;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_friends_and_threads);
        list = (ListView) findViewById(R.id.list);
        mContext = LandingPageActivity.this;

        mAdapter = new SimpleCursorAdapter(this, android.R.layout.simple_list_item_1, null,
                new String[] { Properties.Title.columnName }, new int[] { android.R.id.text1 }, 0);

        list.setAdapter(mAdapter);
        getSupportLoaderManager().initLoader(0, null, this);
    }

    @Override
    public Loader<Cursor> onCreateLoader(int arg0, Bundle arg1) {
        Context c = mContext;
        String query = "SELECT * FROM TABLE_NAME";
        SQLiteOpenHelper db = DatabaseHelper.getDatabase();
        loader = new SQLiteCursorLoader(c, db, query, null);
        return loader;
    }

    @Override
    public void onLoadFinished(Loader<Cursor> arg0, Cursor arg1) {
        mAdapter.changeCursor(arg1);
    }

    @Override
    public void onLoaderReset(Loader<Cursor> arg0) {
        mAdapter.changeCursor(null);
    }
}

the problem starts when the database is changed from a 'BroadcastListener' while the activity is still running.

basically what I'm looking for is real-time observing of the database changes but it seems (also from the Android Documentation that I need to call the restartLoader function when I want to re-query the db).

is there a way to automate re-query behind the scenes?

UPDATE:

My initial thought was to create a function that restarts the loader, something like this:

public static void restartLoader(Context context){
    context.getSupportLoaderManager().restartLoader(0, null, LandingPageActivity.this);
}

but it seems crud and not the best way of doing this.

Immunoreaction

I'd like to suggest: when the underlying database contents have changed, broadcast an event (that your activities may register to receive). When your activity receives the event the Loader is restarted. Using this approach, activities show the latest data and remain decoupled from the rest of your code. – Solitta

Answer 1

the problem starts when the database is changed from a 'BroadcastListener' while the activity is still running... is there a way to automate re-query behind the scenes?

Have the BroadcastReceiver use the insert(), update(), replace(), and delete() methods on SQLiteCursorLoader to modify the database. Then, the Cursor will be re-loaded automatically.

Opisthognathous

only problem with that is that I now need to monitor if the Activity is still alive and instead of the loader observing the DB, now the app needs to observe the loaderActivity that observes the DB. I already have a DAO for the database and all the inserts are being done through it. the loader is just for showing the data and not for the insertions – Immunoreaction

@thepoosh: Sorry, but that's one of the limitation of the Loader framework. It is also the reason why I rarely use it, despite having written things like SQLiteCursorLoader. – Opisthognathous

can I use DatasetObserver on your SQLiteCursorAdapter? – Immunoreaction