How to scroll to the View Controller top and display a Large Title?-CodePudding

I have a ViewControllerOne with a tableView constrained to a superview and filled with a content. User can scroll down some content, then switch to ViewControllerTwo and change tableView data source content on another.

When that happens and user returns to the ViewControllerOne I want the VC to be reset on its initial state at the top with a Large Title and a new content, but with a workaround I found it scrolls only till the tableView top and stops on a Small Title.

Here is the code:

When user picks a new Data Source in ViewControllerTwo I save it as a bool in UserDefaults:
```
  UserDefaults.standard.set(true, forKey: "newDataSourcePicked")
```

In ViewControllerOne I trigger the scrolling method in a viewWillAppear():

   override func viewWillAppear(_ animated: Bool) {
      super.viewWillAppear(animated)
       scrollVCUp()
   }

Here is scrollVCUp(). Here I use the saved bool. Also use delay because its not scrolling without it:

 func scrollVCUp() {
 if newDataSourcePicked {
     traitCollection.verticalSizeClass == .compact ? setVCOffset(with: view.safeAreaInsets.top, and: updateLabelTopInset, delayValue: 0.1) : setVCOffset(with: biggestTopSafeAreaInset, and: updateLabelTopInset, delayValue: 0.1)
     UserDefaults.standard.set(false, forKey: "newDataSourcePicked")
 }
}

Here is setVCOffset():

 func setVCOffset(with viewInset: CGFloat, and labelInset: CGFloat, delayValue: Double = 0.0) {
    let firstVC = navigationController?.viewControllers.first as? CurrencyViewController
    guard let scrollView = firstVC?.view.subviews.first(where: { $0 is UIScrollView }) as? UIScrollView else { return }

 if delayValue > 0.0 {
     DispatchQueue.main.asyncAfter(deadline: .now()   delayValue) {
         scrollView.setContentOffset(CGPoint(x: 0, y: -(viewInset - labelInset)), animated: true)
     }
 } else {
     scrollView.setContentOffset(CGPoint(x: 0, y: -(viewInset - labelInset)), animated: true)
 }
 }

I also have a tabBar and when I use the same code to scroll ViewControllerOne by tapping on a tabBar it scrolls and shows a Large Title, but doesn't work if we switch to another VC and back.

Here is a gif:

What should I do to scroll and always show a Large Title?

CodePudding user response：

Try instead of using

scrollView.setContentOffset(CGPoint(x: 0, y: -(viewInset - labelInset)), animated: true)

I think you should use

scrollView.setContentOffset(.zero, animated: true)

CodePudding user response：

Didn't find any reasonable explanation for my case, but repeating the same code with a little delay one more time fix the issue and after the second code run Large Title appears on scroll.

    func scrollVCUp() {
    if needToScrollUpViewController {
        traitCollection.verticalSizeClass == .compact ? setVCOffset(with: view.safeAreaInsets.top, and: updateLabelTopInset, delayValue: 0.01) : setVCOffset(with: biggestTopSafeAreaInset, and: updateLabelTopInset, delayValue: 0.01)
        traitCollection.verticalSizeClass == .compact ? setVCOffset(with: view.safeAreaInsets.top, and: updateLabelTopInset, delayValue: 0.40) : setVCOffset(with: biggestTopSafeAreaInset, and: updateLabelTopInset, delayValue: 0.40)
    }
}