UICollectionViewController + UITextField autoscroll behavior

Question

Created Sep ’21

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Hi all! I have a UICollectionViewController with cells that contain UITextField items. On iOS 14, switching firstResponder status between each text field programmatically caused the UICollectionView to auto-scroll the items into view.

On iOS 15 this behavior still occurs, but the animation is jittery. The scrollview jumps up and down rapidly while the animation occurs.

As a sanity check, I have no other code executing while this animation occurs. The contentInsets and contentOffset are only being affected by the firstResponder animation.

Any ideas why this might be happening?

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Answer 1

Claude31 OP

Sep ’21

Is it on device or on simulator ?

Is it exactly the same code you run on iOS 14 and iOS 15 ? Did you recompile with another version of Xcode ?

Do you test on the same model of iPhone ? Otherwise, that could be a constraints issue.

Could you show the code where you change firstResponder ?

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Answer 2

mbciarlo OP

Sep ’21

• This is on both an iPhone 12 and the simulator.

• This is the same code on both operating systems.

• I was previously using Xcode 12, but upgraded to the the Xcode 13 RC.

• I'm testing on the same model (both simulator and my personal dev device are iPhone 12s)

• The code where I change first responder is pasted below.

- (void)didPressNextButton {
    if (currentReponderIndex == self.textFields.count - 1) {
        NSNumber *tag = [self.textFields firstObject];
        UITextField *field = [self.view viewWithTag:tag.integerValue];
        [field becomeFirstResponder];

    } else {
        NSNumber *tag = [self.textFields objectAtIndex:currentReponderIndex + 1];
        UITextField *field = [self.view viewWithTag:tag.integerValue];
        [field becomeFirstResponder];
    }
}

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Answer 3

Claude31 OP

Sep ’21

How much jitter do you get ? a few pixels or much more ? Is it when the cell is not completely visible or is it in all cases ?

I found this: could it help ?

h t t p s : / / stackoverflow.com/questions/17435805/uicollectionview-activating-scrolling-to-and-assigning-first-responder-to-dis

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Answer 4

Claude31 OP

Sep ’21

More questions than answers, sorry…

Did the problem occur with Xcode 12 ?
Could you show any code for Collection layout ?
Could be that iOS uses values to scroll before adapting to correct cell sizes ? That's just a guess.
Are all the cells of the same size ?
Have you a minimum example to try and reproduce ?

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Answer 5

mbciarlo OP

Sep ’21

• I don't recall seeing this issue in the two months of previous testing on iOS 14 using Xcode 12.

• I'm using UICollectionViewCompositionalLayout with estimated heights that are about the same size as the rendered rows. I also have header and footer boundary elements.

• I thought it could be a layout pass as well, but when scrolling to the fields on my own, I don't see any jitter. It's only when the keyboard is visible and the system attempts to scroll the view.

• All the cells are the same size.

• I have prepared a minimum example and the issue is reproducible. dropbox.com/s/fpqy2tx7gpvdd69/CollectionViewTesting.zip?dl=0

I have submitted a bug report to Apple with this example project. ID is FB9640529.

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