Previously the app supported the iPhone 5s/SE screen and iPhone 6-8 screens (not the plus sizes), this was done using launch images. So on Plus sized devices and iPhone X* devices it would display black bars above and below the app.
We then released an update where among other things a launch storyboard was added. All through the development of this update the screen size worked perfectly on every device we had. However after releasing the update on the App Store, for some users, the app now shows at iPhone 4 size (height/width ratio is 1.5). So now affected users on an SE have the black bars, and X* users have bigger black bars the before. This doesn't seem to affect everyone, and we can't replicate on our devices.
The deployment target is 10, so there should be no reason to use the old launch images method. And the update is definitely using a storyboard for the launch screens.
Has a similar thing happened to anyone else? Or is there something you have to do specially when releasing an update that moves to the storyboard method from individual launch images?
All the existing answers either say to make sure you have the correct screenshots, or use a xib/storyboard. We don't have any screenshots and are definitely using a storyboard.
EDIT: now after a few hours of restarting the app users are starting to see the correct sizes, implying it’s an iOS caching issue.
I have experienced it lot before.
Reason: iOS commonly keeps launch screens of all apps in its own cache system, So, unless your app get loaded,it can show that launch images/screen to user from cache. Now, As your app was previously having launch images and now moved to storyboard, it makes this problem.
Also note that, iOS always render your app in screensize which it have in launchscreen, thats why you are seeing black bars at top and bottom.
Way to reproduce: This will happen everytime you update your launch screen. Try adding some label or some other component to your launchscreen.storyboard and install it. You will not see updated launch screen for some duration.
Best Solution(It works almost for all): Just update your app's version number and install on the device. After version number get updated, it will take new updated resources.
If above solution didn't worked for you, then you can try for these alternate solutions:
Solution 01: Your user might have to delete older app and install new one
Solution 02: Your user needed to reboot their device after update.
Solution 03: iOS System itself refreshes its own cache after certain interval, so your customers might face issue just after updating... but will get resolved automatically after some duration(around 3-4 hours).
I experienced similar issues with LaunchScreen Storyboard changes and when switching from Launch Images. It is an iOS Bug, sometimes you need to reboot the device in order to see the correct LaunchScreen when changes are made, it is very odd and difficult to reproduce. Most probably there is nothing wrong with your App...
Yes Jonathan, it has happened to others as well.
Sadly it seems that this is a real iOS issue, the problem is real (those negationists please believe).
I called the Apple Support and the developer/support staff that I talked with, seemed aware and/or heard the issue, although the response was unclear I did, nonetheless, report the issue properly. "They will check it out". Typical Apple sideways answer...
Now, current solutions:
It seems that what has worked is the On/off iPhone solution, drastic and heavily inconvenient but currently it's the only workaround "tested".
I am deeply sorry for not solving you inquire straight, but I think this affair is beyond any of us developers field of action, it seems (yet to confirm) an OS problem, which Apple and only Apple can fix for real.
来源：https://stackoverflow.com/questions/54639233/iphone-app-is-running-at-iphone-4-size-with-black-bars-after-update