问题
I am getting constraint warnings for my Navigation Bar's for each of my Navigation Controllers in each of my storyboards in Xcode 8.
To get rid of the warning I set the Navigation Controller's Simulated Metrics->Top Bar setting from Inferred to None and then back again, and the warning goes away. Until the next time the storyboard is opened, then the warnings come back.
My storyboard has the iPhone SE display setting, and the navigation bar's are not Translucent.
回答1:
Changing the device preview from iPhone SE also removes the warning.
Xcode 8 has some serious bugs in Interface Builder: as well as this one, it has a nasty habit of random-seeming frame changes to all sorts of views - in my Main.storyboard, it decided to make some keyboard input accessory views 1,000 by 1,000 points, and everything inside it had a frame of {0,0} - {1000,1000}.
Did the same thing to various UITableViewCells, but not all of them.
Changing everything back took ages, cleaned the build folder and recompiled, but the problem came back straight away as soon as the storyboard was opened.
I had to uninstall 8 and go back to 7.3.1, I filed a radar, saw other people with the same problem on the dev forums.
回答2:
I encountered with the same problem. I am not sure that is solution or not but I just changed the Simulated Metrics size which is page size from freeform to the Page Sheet and warning dissappeard
回答3:
Regarding the issues of Xcode automatically moving some views/subviews to {0, 0, 1000, 1000} frame bug, which is related to main question:
I had the same problem. Make sure to use Xcode 8.1 now as this problem is fixed in that version.
Xcode 8.1 Release notes https://developer.apple.com/library/content/releasenotes/DeveloperTools/RN-Xcode/Introduction.html
Radars related : 28221021, 28244619
Update - Pointing the explicit frame bug solved on Xcode 8.1
来源：https://stackoverflow.com/questions/39492765/xcode-8-storyboard-warnings-for-navigation-bar-width