Question

So I have my MainDisplayActivity which implements both Activity and LoaderManager.LoaderCallbacks<Cursor>. Here I have A ListView, which I fill with Agenda information that I get from my database using a ContentProvider. I also have a GridView which is a calendar. I have it set up when clicking a cell, that the agenda is updated with the day clicked. My problem is that when reusing the Loader I created in onCreate() inside of the setOnItemClickListener(), it does not refresh the information with the new cursor I am creating. I can just create a new Loader with another ID, and it works once, but once I click another day, it stops refreshing. The problem, lies in the cursor. How can I refresh a cursor from a Loader so I don’t have to keep creating a new Loader? Thanks in advance!

Initial call to create the Loader in onCreate() in My MainDisplayActivity class:

makeProviderBundle(new String[] {"_id, event_name, start_date, start_time, end_date, end_time, location"},
            "date(?) >= start_date and date(?) <= end_date", new String[]{getChosenDate(), getChosenDate()}, null);
    getLoaderManager().initLoader(0, myBundle, MainDisplayActivity.this);

    list.setAdapter(agendaAdapter);

These are the overridden methods from LoaderCallbacks<Cursor>

@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    Uri baseUri = SmartCalProvider.CONTENT_URI;
    return new CursorLoader(this, baseUri, args.getStringArray("projection"), 
            args.getString("selection"), args.getStringArray("selectionArgs"), args.getBoolean("sortOrder") ? args.getString("sortOrder") : null );
}



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



@Override
public void onLoaderReset(Loader<Cursor> arg0) {
    //Not really sure how this works. Maybe I need to fix this here?
    agendaAdapter.swapCursor(null);

}

public void makeProviderBundle(String[] projection, String selection, String[] selectionArgs, String sortOrder){
    /*this is a convenience method to pass it arguments 
     * to pass into myBundle which in turn is passed 
     * into the Cursor loader to query the smartcal.db*/
    myBundle = new Bundle();
    myBundle.putStringArray("projection", projection);
    myBundle.putString("selection", selection);
    myBundle.putStringArray("selectionArgs", selectionArgs);
    if(sortOrder != null) myBundle.putString("sortOrder", sortOrder);
}

Any additional code needed please do not hesitate to ask. Thanks again for any help!

Answer 1

You just need to move your code around a little and call restartLoader. That is,

1. When the user clicks a list item, you somehow change the private instance variable that is returned in getChosenDate() (I am being intentionally vague here because you didn’t specify what exactly getChosenDate() returns).

2. Once the change is made, call getLoaderManager().restartLoader() on your Loader. Your old data will be discarded and restartLoader will trigger onCreateLoader to be called again. This time around, getChosenDate() will return a different value (depending on the list item that was clicked) and that should do it. Your onCreateLoader implementation should look something like this:

   @Override
   public Loader<Cursor> onCreateLoader(int id, Bundle args) {
       Uri baseUri = SmartCalProvider.CONTENT_URI;
   
       makeProviderBundle(
           new String[] { "_id, event_name, start_date, start_time, end_date, end_time, location" },
           "date(?) >= start_date and date(?) <= end_date", 
           new String[]{ getChosenDate(), getChosenDate() }, 
           null);
   
       return new CursorLoader(
               this, 
               baseUri, 
               args.getStringArray("projection"), 
               args.getString("selection"), 
               args.getStringArray("selectionArgs"),    
               args.getBoolean("sortOrder") ? args.getString("sortOrder") : null);
   }
   

Let me know if that makes sense. 🙂