UI: Headline disappears

[Ein-Tim]

Avoid duplicates

• [X] Bug is not mentioned in the FAQ
• [X] Bug is specific for iOS only, for general issues / questions that apply to iOS and Android please raise them in the documentation repository
• [X] Bug is not already reported in another issue

Technical details

• Device name: iPhone XR
• iOS version: 14.7.1
• App version: 2.7.1

Describe the bug

When swiping back from the "My QR Codes" screen, the headline disappears:

https://user-images.githubusercontent.com/67682506/129716156-14b20983-b9e7-4c51-ac15-b90754d8e427.mov

Steps to reproduce the issue

1. Open the Corona-Warn-App
2. Scroll down to the "Planning an event?" box
3. Click on "Create QR Code"
4. Swipe back as shown in the video

Expected behaviour

The headline should not disappear

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Internal Tracking ID: EXPOSUREAPP-9029

[dsarkar]

@Ein-Tim Thanks. Internal Tracking ID: EXPOSUREAPP-9029

[ndegendogo]

Also here: cwa 2.7.2 (0) / iOS 14.4.1 / iPhone 8

Similar effect with screen "App Information"

[ndegendogo]

@Ein-Tim do you know if it is possible to reproduce this gesture on the simulator?

[ndegendogo]

And the screen transitions mentioned in #2743 show the same effect - only they additionally change their title size (from large to normal).

[dsarkar]

@ndegendogo Thanks, additional information forwarded to internal ticket.

[Ein-Tim]

@ndegendogo

@Ein-Tim do you know if it is possible to reproduce this gesture on the simulator?

I can reproduce it by swiping from the very left border of the iPhone to the right. Are you able to reproduce it?

[ndegendogo]

I can reproduce it by swiping from the very left border of the iPhone to the right.

Got it - thanks, @Ein-Tim

@dsarkar @heinezen could you please ask the devs if they are already working on this one and/or on #2743? Else I would volunteer to analyse it.

[ndegendogo]

A few observations:

• the scenario is a swiping gesture to pop a view controller from its navigation stack.
• the affected view controller prefers a large title, but its sibling does not. So we have a transition from large to normal title size.
• The transition from the view controller to the previous is animated, but the title size does not participate in this animation.
• All scenarios with this bug occur on the first tab (the 'Home' tab)
• AppNavigationController acts as navigation controller for the 'Home' tab.
• the same class is extended and acts also as UINavigationControllerDelegate, and animates the appearance of the navigation bar during a transition between view controllers on the navigation stack.
• transitions from a large title to another large title work well. Example: from 'Error reports' back to 'App information'.

[ndegendogo]

UIKit provides the following elements for handling of large titles:

• the navigation bar can be configured to support large titles (UINavigationBar.prefersLargeTitles). Note that the navigation bar is shared between the sibling view controllers (these siblings are pushed in from the side).
• each of these view controller has its own navigation item which it configures with its title and layout preferences (UINavigationItem.largeTitleDisplayMode).
• in the current implementation the view controllers permanently re-configure the shared navigation bar to their own preferences in their viewWillAppear method.

A better solution seems to setup the navigation bar only from its owner (the navigation controller), and the view controllers don't fiddle with it and only setup their navigation item. BUT: it seems that the UIKit API has a bug (or hard-to-understand usage) if this view controller is a UITableViewController (if you google you find tons of Voodoo recipes and all seem to help in specific circumstances only)...

I continue to investigate this...

[dsarkar]

@ndegendogo forwarded all to internal ticket. Thanks.

[ndegendogo]

@dsarkar I have played a bit with both tickets on the weekend. Currently I have no good solution, but I'll continue to investigate.

[Ein-Tim]

As the CWA project went into ramp-down mode & this is only a minor issue, I don't expect it to be addressed anymore. I'm therefore closing this issue.