问题
This error is logged to the console when some part of the code is changing UI items from other threads than the main thread. But how can I find where it does this?
回答1:
Main problem with "This application is modifying the autolayout engine from a background thread" is that it seem to be logged a long time after the actual problem occurs, this can make it very hard to troubleshoot.
I managed to solve the issue by creating three symbolic breakpoints.
Debug > Breakpoints > Create Symbolic Breakpoint...
Breakpoint 1:
Symbol:
-[UIView setNeedsLayout]Condition:
!(BOOL)[NSThread isMainThread]
Breakpoint 2:
Symbol:
-[UIView layoutIfNeeded]Condition:
!(BOOL)[NSThread isMainThread]
Breakpoint 3:
Symbol:
-[UIView updateConstraintsIfNeeded]Condition:
!(BOOL)[NSThread isMainThread]
With these breakpoints, you can easily get a break on the actual line where you incorrectly call UI methods on non-main thread.
来源：https://stackoverflow.com/questions/45689126/how-to-solve-this-application-is-modifying-the-autolayout-engine-from-a-backgro