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POSmooth animation of UITableView when removing section
 

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    <h2>tl;dr</h2> <p>When deleting a section in a UITableView while the scroll offset is somewhere in the middle of the table the flow of animation goes like this -</p> <ol> <li>The contentOffset is set to (0,0) immediately (no animation, just pops up)</li> <li>The section fades away nicely</li> </ol> <p>I'd like to make this animation flow a bit better - fade away the section and only afterwards (or simultaneously in a smooth way) scroll the "dead zone" of the table back up.</p> <h2>A bit more explaining</h2> <p>I'm using NSFetchedResultsController as a data source for UITableView to display rows and update the table when changes occur in the NSManagedObjectContext - like this (I removed unrelated code) -</p> <pre><code>- (void)controller: (NSFetchedResultsController *)controller didChangeObject: (id)anObject atIndexPath: (NSIndexPath *)indexPath forChangeType: (NSFetchedResultsChangeType)type newIndexPath: (NSIndexPath *)newIndexPath { UITableView *tableView = self.tableController.tableView; switch(type) { .... NSFetchedResultsChangeDelete:[tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade]; break; ... } } </code></pre> <p>I got all the boilerplate of <code>controllerWillChangeContent</code> and <code>controllerDidChangeContent</code>, the result of this code is that if all the rows in a specific section are removed - the section is also removed.</p> <p>The problem (as I specified in the tl;dr section) is that the animation doesn't work as expected - If the section removal happen while scrolled half-way into the removed section, the scroll content changed immediately and the section fades away, which looks pretty broken.</p> <p>Anyone ever stumbled on a situation like this? I'm sure I can narrow it down to a generic problem without using NSFetchedResultsController, that's jus the code I'm currently using.</p> <p>I'd gladly add more information if needed.</p> <p>Thanks!</p> <h2>Update 1</h2> <p>So after a bit playing with the contentOffset manually I can get something partly working when doing this flow - </p> <ol> <li>When the <code>NSFetchedResultsController</code> calls <code>controllerWillChangeContent</code> I save the UITableView contentOffset (before <code>beginUpdates</code>)</li> <li>When the <code>controllerDidChangeContent</code> is called and right after I call <code>endUpdates</code> I save the contentOffset of the table (this is the offset that wasn't animated)</li> <li>I scroll back to the original contentOffset I saved in part 1 and use <code>[tableView setContentOffset:offsetAfterEndUpdates animated:YES]</code> to scroll to the new offset</li> </ol> <p>This <strong>cannot</strong> be the best solution / what Apple ment.</p>
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    1. USNimrod Gutman
    1. USNimrod Gutman
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    1. COthe normal tableView behavior is: The contentOffset remains as it is (if possible), else it is animated to the new (smaller) value. Within the same Animation-Block the Section/Rows are removed with the specified `UITableViewRowAnimation`. So Either the `NSFetchedResultsController` is messing up this behavior or some of your code does.
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      1. USJonathan Cichon
    2. COThat's interesting, I'd take a closer look at the code and see if I mess the default animation somehow
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      1. USNimrod Gutman
 

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