UITableView :scrollToRowAtIndexPath or setContentOffset animation speed

Question

Lets say i have 10 rows displaying numbers 1 to 10. I need scrolling effect like 1 to 10 to 1to 10... I achieved this using scrollToRowAtIndexPath and setContentOffset. The issue i want to slow down the scrolling before i apply my logic to stop this recursion. So is there a way that i can decrease the scroll speed for scrollToRowAtIndexPath. ? Please do not suggest, decelerationRate as scrolls here are all programmatic, no user interactions. Thanks in advance.

score 2 · Answer 1 · edited May 23 '17 at 12:08

2

Just call your scrollToRowAtIndexPath or setContentOffset methods inside +(void)animateWithDuration:animations: block.

Check these answers for more details:

Change the speed of setContentOffset:animated:?

scrollToRowAtIndexPath:atScrollPosition:animated scrolling too slow

edited May 23 '17 at 12:08

Community

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answered Jun 04 '16 at 18:05

Alex Kosyakov

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Frane Poljak · Accepted Answer · 2016-06-06T18:00:28.837

1

You can do something like this:

[UIView animateWithDuration:durationInSeconds animations:^(void){
    [tableView setContentOffset:offset animated:NO];
}];

You just need to calculate the offset. If your rows have equal heights, then your offset is simply calculated:

CGPoint offset = CGPointMake(0, indexPath.row * rowHeight);

and if the height varies then you need to do this:

CGFloat offsetY = 0;

for (NSInteger i = 0; i <= indexPath.row; i++) {
    offsetY += [tableView.delegate tableView:tableView heightForRowAtIndexPath:indexPath];
}

CGPoint offset = CGPointMake(0, offsetY);

EDIT:

You can also use scrollToRowAtIndexPath:animated: method with animated set to NO in the animation block instead of setContentOffset, and then you don't have to calculate the offset yourself.

edited Jun 06 '16 at 18:00

answered Jun 04 '16 at 18:23

Frane Poljak

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Sounds good. Do u mean that once i decide to slow down, i come out of my circular scroll recursion logic and do the above to reach my intended row which will give a slow scroll effect? – Avi Jun 04 '16 at 18:35
Yes, this is to slow down the scrolling, and you set the duration with 'durationInSeconds' parameter in animateWithDuration method. As Alex suggested in another answer, you can also use scrollToRowAtIndexPath:animated: method with animated set to NO in the animation block instead of setContentOffset, and then you don't have to calculate the offset yourself. – Frane Poljak Jun 05 '16 at 16:58
Yeah, Tried that. WOrks. – Avi Jun 05 '16 at 18:07

UITableView :scrollToRowAtIndexPath or setContentOffset animation speed

2 Answers2