UIScrollView setContentOffset：动画：不工作

Question

I have a problem with two infinite UIScrollViews which do not change their offsets properly.

An item in the first UIScrollView corresponds with another one in the second. Then, I want to put the clicked item in the second place and animate the change in both UIScrollView. To get this done properly, I use this two methods:

When item is clicked:

- (void)click:(id)sender {
    NSInteger index = [[self cells] indexOfObject:sender];
    if (index == 1)
    {
        CategoriesViewController *viewController = [[CategoriesViewController alloc] initWithNibName:@"CategoriesView" bundle:nil];

        [[viewController tit] setText:NSLocalizedString([[self categories] objectAtIndex:1], nil)];

        [[self navigationController] pushViewController:viewController animated:YES];
    }
    else
    {
        for (NSInteger i = 0; i < index - 1; i++)
        {
            NSObject *object = [[self categories] objectAtIndex:0];
            [[self categories] removeObjectAtIndex:0];
            [[self categories] addObject:object];
        }

        for (NSInteger i = 0; i < index - 1; i++)
        {
            CollectionCellViewController *cell = [[self cells] objectAtIndex:0];
            [[self cells] removeObjectAtIndex:0];
            [[self cells] addObject:cell];
        }

        for (NSInteger i = 0; i < index - 1; i++)
        {
            UIImageView *image = [[self images] objectAtIndex:0];
            [[self images] removeObjectAtIndex:0];
            [[self images] addObject:image];
        }

        [self updateViewsOffsets];
    }
}

- (void)updateViewsOffsets {
    NSInteger y = 0;
    for (NSInteger i = 0; i < [[self cells] count]; i++)
    {
        CollectionCellViewController *cell = [[self cells] objectAtIndex:i];

        [[cell view] setTag:i];
        if (i == 1)
        {
            [cell setSelected:[[self categories] objectAtIndex:i]];
        }
        else
        {
            [cell setDeselected:[[self categories] objectAtIndex:i]];
        }

        CGRect rect = [[cell view] frame];
        rect.origin.x = 0.0f;
        rect.origin.y = y;
        [[cell view] setFrame:rect];
        y += [[self table] frame].size.height / 2.0f;
    }

    y = 0;
    for (NSInteger i = 0; i < [[self images] count]; i++)
    {
        UIImageView *image = [[self images] objectAtIndex:i];
        CGRect rect = [image frame];
        rect.origin.x = 0.0f;
        rect.origin.y = y;
        [image setFrame:rect];
        y += [[self gallery] frame].size.height;
    }

    [[self table] setContentOffset:CGPointMake(0.0f, [[self table] frame].size.height / 2.0f) animated:YES];
    [[self gallery] setContentOffset:CGPointMake(0.0f, [[self table] contentOffset].y * 8.0f) animated:YES];
}

The change is made, but without animation, it have the same behaviour with YES or NO, it only calls scrollViewDidScroll: once. However, I use setContentOffset: animated: in other methods where it works properly with both UIScrollView.

Any idea, please. Thank you very much in advance.

Answer 1

I just had this issue. I fixed it by dispatching the call to the main thread. Try this:

dispatch_async(dispatch_get_main_queue(), ^{
    [[self table] setContentOffset:CGPointMake(0.0f, [[self table] frame].size.height / 2.0f) animated:YES];
    [[self gallery] setContentOffset:CGPointMake(0.0f, [[self table] contentOffset].y * 8.0f) animated:YES];
});