scroll to top doesn't work correctly

[arashetm]

Describe the bug
scroll to the top doesn't work correctly.

To Reproduce
create a tableView including too many items.
scroll to the middle of tableView and then call this:

if let navigationController = self.navigationController as? ScrollingNavigationController {
    navigationController.showNavbar(animated: true, duration: 0.2, scrollToTop: true)
}

It scrolls to top but not actually to top of tableView.

[andreamazz]

See #377 and #378

[arashetm]

Didn't help me!
It doesn't work properly.
Actually I call the showNavbar method in the action of segmentValueChanged.

[andreamazz]

Hi @arashetm
I'm testing against the Demo project, attached the segment action like so:

  @IBAction func segmentChange() {
    if let navigationController = self.navigationController as? ScrollingNavigationController {
      navigationController.showNavbar(animated: true, duration: 0.2, scrollToTop: true)
    }
  }

and it seems to be working fine. Can you share a sample project showing the issue?

[arashetm]

I figured out what's the problem!
If I want to scroll to the top without changing segment it works like charm, but if I want to update my table view data source alongside scrolling to the top it doesn't work properly.
Here is my code:

@IBAction func segmentValueChanged(_ sender: UISegmentedControl) {
    _ = self.scrollViewShouldScrollToTop(self.archiveTableView)
    self.setBannersFrame()        //setting table header view
    // change table view's data based on the selected segment
    self.reloadArchiveTableView() // reloading table view
}

I found a hacky slution for this::

@IBAction func segmentValueChanged(_ sender: UISegmentedControl) {
    _ = self.scrollViewShouldScrollToTop(self.archiveTableView)
    self.setBannersFrame()        //setting table header view
    // change table view's data based on the selected segment
    DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
        self.reloadArchiveTableView() // reloading table view
    }
}

Maybe you need to add completion handler for showNavbar method.

[andreamazz]

Sounds good, checkout the latest master commit for the completion handler in showNavbar

[arashetm]

It didn't work ...

[andreamazz]

I'm afraid it's still triggered too early, before UIKit rearranges the table

[arashetm]

Do you have any suggestions?
Reloading should start exactly right after scroll did end scrolling, could we use scrollViewDidEndScrollingAnimation?
I need to achieve this.

[andreamazz]

Checkout the updated demo in master, the tableview now scrolls to top and updates the data source, and it seems to be working. Maybe it helps, let me know
b280a88#diff-42fa19733453bd36493bea5901519e2d

[andreamazz]

Any feedback?

[uzman]

you can fix it by calling collectionview's scrolltoItem method in the completion block:

    open func scrollViewShouldScrollToTop(_ scrollView: UIScrollView) -> Bool {
        if let navigationController = self.navigationController as? ScrollingNavigationController {
            navigationController.showNavbar(animated: false, duration: 0.1, scrollToTop: false) {
                DispatchQueue.main.asyncAfter(deadline: .now() + 0.2) {
                    self.collectionView.scrollToItem(at: IndexPath(row: 0, section: 0), at: .top, animated: true)
                }
            }
        }
        return true
    }