CODEWITHSUNDEEP
iosswiftuitableviewuitableviewautomaticdimension
Dracula
Dracula

Reputation: 3090

Tableview scrollToRow(at:at:animated) causing scrollViewDidScroll(_) to be called multiple times

I have checked all possibilities as to why my UITableView is behaving so oddly for the whole day. Finally, right now I noticed something strange. I needed some help in figuring out if what I noticed is true or the problem could be in someplace else.

So in tableView(_:didSelectRowAt:), I want to scroll to a particular cell after resizing the heights of all the cells. (I am increasing the heights of all the cells.)

This is a small relevant part of my scrollViewDidScroll(_) method body that is responsible for deciding which part of the section of screen was tapped (I need this for some other stuff to work):

public func scrollViewDidScroll(_ scrollView: UIScrollView) {        
   let touchLocation = scrollView.panGestureRecognizer.location(in: containerView)
   let touchX = touchLocation.x
   print("X: \(touchX)")
  .
  .
  .
}

Now in my didSelectRowAt, when I call scrollToRow as:

tableView.scrollToRow(at: indexPath, at: .top, animated: false)

I get this as output:

X: 132.0 (old touch x)
X: 130.66665649414062 (old touch x when scrolling stopped)
X: 188.66665649414062 (new touch x of tap)
X: 188.66665649414062 (not sure why this was printed again)

But now when I execute the scrollToRow as:

tableView.scrollToRow(at: indexPath, at: .top, animated: true)

X: 160.3333282470703
X: 160.3333282470703 (new touch x of tap)
X: 177.66665649414062
X: 177.66665649414062
X: 177.66665649414062
X: 177.66665649414062
X: 177.66665649414062
X: 177.66665649414062
X: 177.66665649414062
X: 177.66665649414062
X: 177.66665649414062
X: 177.66665649414062
.
.
.
174 times .
.
.
X: 177.66665649414062

This is very strange. Can someone explain why this could be happening?

Upvotes: -2

Views: 637

Answers (2)

EmilioPelaez
EmilioPelaez

Reputation: 19912

scrollViewDidScroll gets called every frame that the scroll view has scrolled, doesn’t matter if it’s done by the user or by calling scrollTo methods. This can be up to, I think, 120 times per second while the user is scrolling.

If you want to do something when the scroll view has stopped, you should use the didEndDeccelerating and didEndScrollingAnimation delegate methods.

Upvotes: 1

viral goti
viral goti

Reputation: 103

Sorry for before answer. maybe this will help, scrollViewDidScroll every time when you scroll tableview so, may be you have to use scrollViewDidEndDragging,scrollViewWillBeginDecelerating,scrollViewDidEndDecelerating

Upvotes: 0

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