CursorLoader not updating after data change

问题

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.

回答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.

回答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.

回答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;
}`

来源：https://stackoverflow.com/questions/7915050/cursorloader-not-updating-after-data-change