LoaderManager.LoaderCallbacks seems not working correctly

Question

I want to Leverage Loaders in my App as

public class ForecastFragment extends Fragment implements LoaderManager.LoaderCallbacks<Cursor>{

    private ListView forecasteListView;
    private SimpleCursorAdapter forecasteAdapter;

    private String mLocation;
    private static final int FORE_CAST_LOADER = 404;

    private static final String[] FORE_CAST_COLUMNS = {
       WeatherContract.WeatherEntry.TABLE_NAME + "." + WeatherContract.WeatherEntry._ID,
       WeatherContract.WeatherEntry.COLUMN_DATE,
       WeatherContract.WeatherEntry.COLUMN_SHORT_DESC,
       WeatherContract.WeatherEntry.COLUMN_MAX_TEMP,
       WeatherContract.WeatherEntry.COLUMN_MIN_TEMP,
       WeatherContract.LocationEntry.COLUMN_LOCATION_SETTING

    };

    public static final int COL_WEATHER_ID = 0;
    public static final int COL_WEATHER_DATE = 1;
    public static final int COL_WEATHER_DESC = 2;
    public static final int COL_WEATHER_MAX_TEMP = 3;
    public static final int COL_WEATHER_MIN_TEMP = 4;
    public static final int COL_LOCATION_SETTING = 5;

    public ForecastFragment() {
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        getLoaderManager().initLoader(FORE_CAST_LOADER, null, this);
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setHasOptionsMenu(true);
    }

    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        inflater.inflate(R.menu.forcast_menu, menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (item.getItemId() == R.id.action_refresh){
           updateWeather();
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    private void updateWeather() {
        FetchWeatherTask forecastWeather = new FetchWeatherTask(getActivity());

        SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getActivity());
        String cityName = sharedPreferences.getString(getString(R.string.pref_city_key),getString(R.string.pref_city_default));
        forecastWeather.execute(cityName, null, null);
    }

    @Override
    public void onStart() {
        super.onStart();
        updateWeather();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        forecasteAdapter = new SimpleCursorAdapter(getActivity(),
                R.layout.list_item_forecast,
                null,
                new String[]{WeatherContract.WeatherEntry.COLUMN_DATE,
                        WeatherContract.WeatherEntry.COLUMN_SHORT_DESC,
                        WeatherContract.WeatherEntry.COLUMN_MAX_TEMP,
                        WeatherContract.WeatherEntry.COLUMN_MIN_TEMP
                },
                new int[]{R.id.list_item_date_textView,
                        R.id.list_item_forecast_desc_textView,
                        R.id.list_item_high_textView,
                        R.id.list_item_low_textView
                }, 0

        );

        Log.e("onCreateView()", "List Adapter is of " + forecasteAdapter.getCount() + " size");

        View rootView = inflater.inflate(R.layout.fragment_main, container, false);    
        forecasteListView = (ListView) rootView.findViewById(R.id.listView_forecast);    
        return rootView ;
    }

    @Override
    public Loader<Cursor> onCreateLoader(int id, Bundle args) {
        String sortOrder = WeatherContract.WeatherEntry.COLUMN_DATE + " ASC";

        mLocation = Utility.getPreferredLocation(getActivity());

        Uri weatherForLocationUri = WeatherContract.WeatherEntry.buildWeatherLocationWithStartDate(mLocation, System.currentTimeMillis());

        Log.e("FORE_CAST_FRAGMENT", "Uri : " + weatherForLocationUri.toString() );
        return new CursorLoader(getActivity(), weatherForLocationUri, FORE_CAST_COLUMNS, null, null, sortOrder);
    }

    @Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
        Log.e("Loader<Cursor>", "Size of Cursor is " + data.getCount());
        forecasteAdapter.swapCursor(data);
    }

    @Override
    public void onLoaderReset(Loader<Cursor> loader) {
        forecasteAdapter.swapCursor(null);
    }
}

the above code runs without errors/exceptions, first when App starts the method

@Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
        Log.e("Loader<Cursor>", "Size of Cursor is " + data.getCount());
        forecasteAdapter.swapCursor(data);
    }

prints

E/Loader<Cursor>﹕ Size of Cursor is 0

and it does not fetch data from database and populate ListView. Any help is greatly welcome in this case.

Disclaimer I'm flowing along with tutorials from Developing Android Apps - By Udacity course.

Or any other way to get data from ContentPrivider using uri and populating a Adapter for List. — Crazy Coder, Oct 26 '15 at 10:16

score 0 · Answer 1 · answered Jan 22 '16 at 06:33

Have you tried to debug you application and check whether the bulk insert worked correctly and inserted data in the table or not.

Because there is no data in the table the cursor will be fetching 0 rows all the time. try to keep some log statements in the Adapter class where the bulk insert query is being executed.If entries are being made then there might be some issue in the URI which you are passing to fetch the data from the table.

Hope this helps you. Cheers.

LoaderManager.LoaderCallbacks seems not working correctly

1 Answers1