问题
I don't know what happened. Elements items like buttons or segmented control are invisible in main storyboard. Cellphone is the same.
I put the image, of what I mean
回答1:
It looks like you accidentally changed the view's (or window's) Tint Color to white. (Or you could even have turned it to Clear color, or no color at all.)
This would cause the text of the button or segmented control to be invisible, because it is white on white. The segmented control has a border but it would turn white too. So you wouldn't be able to see anything.
There are two places to look to fix this. Look at the Tint popup of your view controller's View in the Attributes inspector.
Also look at the Global Tint popup in the File inspector for the whole storyboard.
[EDIT It turned out to be the Global Tint.]
来源：https://stackoverflow.com/questions/52415131/xcode-invisible-elements