UITableView scroll to wrong position when keyboard shows - ios

Question

Although UITableViewController can automatically adjust table view when keyboard shows, it's not flexible enough. I try to use a UIViewController and UITableView to build my UI.
There are many cells in the table view. Among all the cells, there is a cell with a UITextField. When I tap that text field, the keyboard shows and the table view does not do anything even if the cell is overlaid by the keyboard. It's OK because this is the expected result.
The strange thing comes. If I give the table view a large contentInset.bottom, e.g. contentInset.bottom = 600, the table view will automatically scroll when keyboard shows.
I try to aviod using tableView.contentInsetAdjustmentBehavior = .never.
The following code shows this strange behavior. It can be reproduced on iOS 14.5, iPhone 12 mini Simulator.
class TestViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
let tableView = UITableView()
override func loadView() {
view = tableView
}
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .white
tableView.delegate = self
tableView.dataSource = self
tableView.contentInset.bottom = 600
}
func scrollViewDidScroll(_ scrollView: UIScrollView) {
print("scrolling contentOffset-Y: \(scrollView.contentOffset.y)")
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 20
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
// Ugly code, only for showing the problem.
let cell = UITableViewCell()
if indexPath.row == 9 {
let textField = UITextField()
cell.contentView.addSubview(textField)
textField.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
textField.leadingAnchor.constraint(equalTo: cell.contentView.layoutMarginsGuide.leadingAnchor),
textField.trailingAnchor.constraint(equalTo: cell.contentView.layoutMarginsGuide.trailingAnchor),
textField.topAnchor.constraint(equalTo: cell.contentView.layoutMarginsGuide.topAnchor),
textField.bottomAnchor.constraint(equalTo: cell.contentView.layoutMarginsGuide.bottomAnchor),
])
} else {
cell.textLabel?.text = "\(indexPath)"
}
return cell
}
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
return 60
}
}

Answer 1

You should add UITextfield delegate to the textfield in the tableview cell to check if keyboard has been launched and let it check for you as shown by the example below:
func textFieldShouldBeginEditing(textField: UITextField) -> Bool {
var pointInTable:CGPoint = textField.superview!.convertPoint(textField.frame.origin, toView:_tableview)
var contentOffset:CGPoint = _tableview.contentOffset
contentOffset.y = pointInTable.y
if let accessoryView = textField.inputAccessoryView {
contentOffset.y -= accessoryView.frame.size.height
}
_tableview.contentOffset = contentOffset
return true;
}
Hope that one helps.