CursorLoader not updating after data change

Question

I have created a small application, trying to understand the functionality of the LoaderManager and CursorLoader-classes.

I have implemented LoaderCallbacks<Cursor> on my FragmentActivity-class and everything works fine, except the fact that when I update my data via ContentResolver.update() or ContentResolver.insert()-methods, onLoadFinished() is not called and as a result my data doesn't update.

I have a custom ContentProvider and I am wondering if the problem is in my ContentProvider not notifying that the data changed or something else.

Chesterton

do you call getContext().getContentResolver().notifyChange(Uri,..); in your update/insert ContentProvider methods implementation ? do you call cursor.setNotificationUri(getContext().getContentResolver(), uri); before return it from query method in your ContentProvider – Huonghupeh

Nope, I didn't, that was the problem! Thanks! :) – Chesterton

Answer 1

Did you call setNotificationUri(ContentResolver cr, Uri uri) on the Cursor before returning it in ContentProvider.query()?

And did you call getContext().getContentResolver().notifyChange(uri, null) in the 'insert' method of your ContentProvider?

EDIT:

To get a ContentResolver call getContext().getContentResolver() in your ContentProvider.

Billiards

Thanks for the fast reply!Seems like this is the problem, how can I get a ContentResolver from the ContentProvider to put it in setNotificationUri()? EDIT: I found it, just use getContext().getCntentProvider() – Chesterton

Annoying that this isn't mentioned when I followed the android dev docs to create a content provider – Upswing

Also, you should NOT call cursor.close() at ANY point in onLoadFinished else you will not receive any further updates to the underlying dataset. – Siegbahn

Does the URI passed to the setNotificationUri() match that of the notifyChange() URI exactly, or does simply have to have the same authority or something? – Enwomb

The URIs have to be equal. – Billiards

YES, YES, YES!! Wish I'd seen this Q&A 24 hours ago - but still very happy to have finally got this nailed! – Latoyia

@Herrmann Is there something else one should be aware of. Namely: I call both setNotificationUri(ContentResolver cr, Uri uri) and notifyChange(uri, null) with the same URI. Yet my list view is not updated. – Diadem

Hmm, do you use a custom cursor? Have you implemented a ContentProvider? – Billiards

@Herrmann Please take a look at #32742134. – Diadem

And you should use getContext().getContentResolver().notifyChange(uri, null) whenever you update your data. I mean insert update delete. – Heyday

Answer 2

Also check if you call somewhere cursor.close(), because in this case you unregister the content observer which was registered by CursorLoader. And the cursor closing is managed by CursorLoader.

Hydrodynamic

This was the missing link in my implementation – Witha

Answer 3

Accepted answer was the little bit tricky to understand so I am writing the answer to make it easy for other developers..

1. Go to the class in which you have extended the ContentProvider

2. Find the query() method which has the following syntax

   public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)

3. Write this line where you are returning the cursor

   cursor.setNotificationUri(getContext().getContentResolver(), uri); return cursor;

In the end, my query method looks like this

@Nullable
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {

    Cursor cursor;
    cursor = noticeDbHelper.getReadableDatabase().query(
            NoticeContract.NoticeTable.TABLE_NAME,
            projection,
            selection,
            selectionArgs,
            null,
            null,
            sortOrder
    );
    //This line will let CursorLoader know about any data change on "uri" , So that data will be reloaded to CursorLoader
    cursor.setNotificationUri(getContext().getContentResolver(), uri);
    return cursor;
}`

Clynes