Weird uitableview behaviour in iOS11. Cells scroll

Question

I have recently migrated some code to new iOS 11 beta 5 SDK.

I now get a very confusing behaviour from UITableView. The tableview itself is not that fancy. I have custom cells but in most part it is just for their height.

When I push my view controller with tableview I get an additional animation where cells "scroll up" (or possibly the whole tableview frame is changed) and down along push/pop navigation animation. Please see gif:

I manually create tableview in loadView method and setup auto layout constraints to be equal to leading, trailing, top, bottom of tableview's superview. The superview is root view of view controller.

View controller pushing code is very much standard: self.navigationController?.pushViewController(notifVC, animated: true)

The same code provides normal behaviour on iOS 10.

Could you please point me into direction of what is wrong?

EDIT: I have made a very simple tableview controller and I can reproduce the same behavior there. Code:

class VerySimpleTableViewController : UITableViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        self.tableView.register(UITableViewCell.self, forCellReuseIdentifier: "Cell")
    }


    override func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 4
    }


    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)

        cell.textLabel?.text = String(indexPath.row)
        cell.accessoryType = .disclosureIndicator

        return cell
    }


    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.deselectRow(at: indexPath, animated: true)

        let vc = VerySimpleTableViewController.init(style: .grouped)

        self.navigationController?.pushViewController(vc, animated: true)
    }
}

EDIT 2: I was able to narrow issue down to my customisation of UINavigationBar. I have a customisation like this:

rootNavController.navigationBar.setBackgroundImage(createFilledImage(withColor: .white, size: 1), for: .default)

where createFilledImage creates square image with given size and color.

If I comment out this line I get back normal behaviour.

I would appreciate any thoughts on this matter.

Answer 1

You can edit this behavior at once throughout the application by using NSProxy in for example didFinishLaunchingWithOptions:

if (@available(iOS 11.0, *)) {
      [UIScrollView appearance].contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
} 

Answer 2

This seems more like a bug than intended behavior. It happens when navigation bar is not translucent or when background image is set.

If you just set contentInsetAdjustmentBehavior to .never, content insets won't be set correctly on iPhone X, e.g. content would go into bottom area, under the scrollbars.

It is necessary to do two things:
1. prevent scrollView animating up on push/pop
2. retain .automatic behaviour because it is needed for iPhone X. Without this e.g. in portrait, content will go below bottom scrollbar.

New simple solution: in XIB: Just add new UIView on top of your main view with top, leading and trailing to superview and height set to 0. You don't have to connect it to other subviews or anything.

Old solution:

Note: If you are using UIScrollView in landscape mode, it still doesn't set horizontal insets correctly(another bug?), so you must pin scrollView's leading/trailing to safeAreaInsets in IB.

Note 2: Solution below also has problem that if tableView is scrolled to the bottom, and you push controller and pop back, it will not be at the bottom anymore.

override func viewDidLoad()
{
    super.viewDidLoad()

    // This parts gets rid of animation when pushing
    if #available(iOS 11, *)
    {
        self.tableView.contentInsetAdjustmentBehavior = .never
    }
}

override func viewDidDisappear(_ animated: Bool)
{
    super.viewDidDisappear(animated)
    // This parts gets rid of animation when popping
    if #available(iOS 11, *)
    {
        self.tableView.contentInsetAdjustmentBehavior = .never
    }
}

override func viewDidAppear(_ animated: Bool)
{
    super.viewDidAppear(animated)
    // This parts sets correct behaviour(insets are correct on iPhone X)
    if #available(iOS 11, *)
    {
        self.tableView.contentInsetAdjustmentBehavior = .automatic
    }
}

Answer 3

Also if you use tab bar, bottom content inset of the collection view will be zero. For this, put below code in viewDidAppear:

if #available(iOS 11, *) {
    tableView.contentInset = self.collectionView.safeAreaInsets
}

Answer 4

Here's how I managed to fix this issue while still allowing iOS 11 to set insets automatically. I am using UITableViewController.

• Select "Extend edges under top bars" and "Extend edges under opaque bars" in your view controller in storyboard (or programmatically). The safe area insets will prevent your view from going under the top bar.
• Check the "Insets to Safe Area" button on your table view in your storyboard. (or tableView.insetsContentViewsToSafeArea = true) - This might not be necessary but it's what I did.
• Set the content inset adjustment behavior to "Scrollable Axes" (or tableView.contentInsetAdjustmentBehavior = .scrollableAxes) - .always might also work but I did not test.

---

One other thing to try if all else fails:

Override viewSafeAreaInsetsDidChange UIViewController method to get the table view to force set the scroll view insets to the safe area insets. This is in conjunction with the 'Never' setting in Maggy's answer.

- (void)viewSafeAreaInsetsDidChange {
    [super viewSafeAreaInsetsDidChange];
    self.tableView.contentInset = self.view.safeAreaInsets;
}

Note: self.tableView and self.view should be the same thing for UITableViewController

Answer 5

This is due to UIScrollView's (UITableView is a subclass of UIScrollview) new contentInsetAdjustmentBehavior property, which is set to .automatic by default.

You can override this behavior with the following snippet in the viewDidLoad of any affected controllers:

    tableView.contentInsetAdjustmentBehavior = .never

https://developer.apple.com/documentation/uikit/uiscrollview/2902261-contentinsetadjustmentbehavior

Answer 6

please make sure along with above code, add additional code as follows. It solved the problem

override func viewDidLayoutSubviews() { 
     super.viewDidLayoutSubviews() 
     tableView.contentInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0) // print(thisUISBTV.adjustedContentInset) 
}