UITableView scrolls up on reloadData - ios

Question

I have a UITableView that gets reloaded if a button in some of its cells gets tapped. The issue appears if the following steps are made:
Tap a button on a cell so that another cells appear below the tapped cell on reloadData.
Scroll up the table view so that it hides some of the upper content.
Tap the button again to hide the cells that were just shown making another call to reloadData.
Then the table view goes up and hides the upper content (the whole first cell and part of the second one). Here is some of the code:
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
if shouldShowImageResolutionOptions && (indexPath.row == 2 || indexPath.row == 3 || indexPath.row == 4) {
return isLastKnownDeviceOrientationLandscape ? 60 : 80
}
if shouldShowImageDisplayOptions && (indexPath.row == 3 || indexPath.row == 4) {
return isLastKnownDeviceOrientationLandscape ? 60 : 80
}
return isLastKnownDeviceOrientationLandscape ? tableView.frame.size.height / 2.5 + 40 : tableView.frame.size.height / 4.5 + 40
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if shouldShowImageResolutionOptions {
return 6
}
if shouldShowImageDisplayOptions {
return 5
}
return 3
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
switch indexPath.row {
case 0:
let cell = tableView.dequeueReusableCell(withIdentifier: CellIdentifiers.IntervalCell) as! IntervalCell
cell.selectionStyle = .none
cell.dottedSliderView.contentMode = .redraw
cell.adjustThumbPosition()
return cell
case 1:
let cell = tableView.dequeueReusableCell(withIdentifier: CellIdentifiers.SettingsCell) as! SettingsCell
cell.selectionStyle = .none
cell.titleLabel.text = LabelTitles.ImageResolution
cell.choiseLabel.text = LabelTitles.HDResolutioin
cell.onButtonTap = {
self.shouldShowImageResolutionOptions = !self.shouldShowImageResolutionOptions
self.shouldShowImageDisplayOptions = false
self.menuTableView.reloadData()
}
return cell
case 2:
if(shouldShowImageResolutionOptions) {
let cell = tableView.dequeueReusableCell(withIdentifier: CellIdentifiers.SingleSettingCell, for: indexPath) as! SingleSettingCell
cell.selectionStyle = .none
cell.mainSettingLabel.text = Settings.HDResolution
return cell
}
let cell = tableView.dequeueReusableCell(withIdentifier: CellIdentifiers.SettingsCell) as! SettingsCell
cell.selectionStyle = .none
cell.titleLabel.text = LabelTitles.ImageDisplay
cell.choiseLabel.text = LabelTitles.EnlargeImage
cell.onButtonTap = {
self.shouldShowImageDisplayOptions = !self.shouldShowImageDisplayOptions
self.shouldShowImageResolutionOptions = false
self.menuTableView.reloadData()
}
return cell
case 3, 4:
if(shouldShowImageResolutionOptions) {
let cell = tableView.dequeueReusableCell(withIdentifier: CellIdentifiers.SingleSettingCell, for: indexPath) as! SingleSettingCell
cell.selectionStyle = .none
cell.mainSettingLabel.text = indexPath.row == 3 ? Settings.HighResolution : Settings.MediumResolution
return cell
} else {
let cell = tableView.dequeueReusableCell(withIdentifier: CellIdentifiers.SingleSettingCell, for: indexPath) as! SingleSettingCell
cell.selectionStyle = .none
cell.mainSettingLabel.text = indexPath.row == 3 ? Settings.ShowFullImage : Settings.EnlargeImage
return cell
}
case 5:
let cell = tableView.dequeueReusableCell(withIdentifier: CellIdentifiers.SettingsCell) as! SettingsCell
cell.selectionStyle = .none
cell.titleLabel.text = LabelTitles.ImageDisplay
cell.choiseLabel.text = LabelTitles.EnlargeImage
cell.onButtonTap = {
self.shouldShowImageDisplayOptions = !self.shouldShowImageDisplayOptions
self.shouldShowImageResolutionOptions = false
self.menuTableView.reloadData()
}
return cell
default:
return UITableViewCell()
}
}

Answer 1

From the UITableView's reloadData method documentation (https://developer.apple.com/documentation/uikit/uitableview/1614862-reloaddata):
The table view’s delegate or data source calls this method when it wants the table view to completely reload its data. It should not be called in the methods that insert or delete rows, especially within an animation block implemented with calls to beginUpdates and endUpdates.
There are dedicated insert/delete rows methods for inserting and deleting:
insertRowsAtIndexPaths:withRowAnimation:(https://developer.apple.com/documentation/uikit/uitableview/1614879-insertrowsatindexpaths)
deleteRowsAtIndexPaths:withRowAnimation: (https://developer.apple.com/documentation/uikit/uitableview/1614960-deleterowsatindexpaths)
So when you refactor your code to use those it should work smoothly and as expected.