Question

I have a ListActivity which uses a SimpleCursorAdapter to display database content. I am having problems getting the view refreshed when the underlying database changes.

As an experiment, I’ve added a call to Cursor.requery() in the activity’s onResume(), for debugging, so all I have to do is flip to a different activity and back and it should force a refresh. I’ve also overridden onContentChanged(), for debugging. It transpires that requery() is being called, but this is not resulting in a call to onContentChanged().

I suspect the cursor is using stale cached data. The operation which prompts the change actually involves wiping and replacing the whole database. Rather than simply requerying, I think I need to throw away the cursor and rebuild it from scratch.

I have tried closing and reopening the underlying database, in conjunction with Cursor.requery(), but the cursor doesn’t seem to like having the db pulled from under its feet like this. (The list ends up empty.)

Edit: I’ve also tried calling adapter.notifyDataSetChanged() alongside the requery() in onResume(), but it makes no difference.

Any advice?

Answer 1

Solved by discarding the cursor, closing and reopening the database, and then recreating the cursor. I use an Observer to inform the activity of the database change, as follows:

@Override 
public void update(Observable observable, Object data) { 
    // database changed 
    runOnUiThread(new Runnable() { 
        @Override 
        public void run() { 
            stopManagingCursor(cursor); 
            dbAdapter.close(); 
            dbAdapter.open(); 
            cursor = getAccounts(); 
            startManagingCursor(cursor); 
            adapter.changeCursor(cursor); 
        } 
    }); 
}