I'm seeing an unexpected auto layout error when a cell moves off screen. Otherwise, the layout looks good, and the layout works 100% when the cell returns to the screen.
Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSLayoutConstraint:0x1769c940 H:|-(>=0)-[UIView:0x1769c740] (Names: '|':UIView:0x1769c6e0 )>",
"<NSLayoutConstraint:0x1769c9b0 H:[UIView:0x1769c740]-(>=0)-| (Names: '|':UIView:0x1769c6e0 )>",
"<NSLayoutConstraint:0x1769efb0 UIView:0x1769c6e0.centerX == UIView:0x1769b4b0.centerX>",
"<NSLayoutConstraint:0x1769f240 H:|-(>=5)-[UIView:0x1769c6e0] (Names: '|':UIView:0x1769b4b0 )>",
"<NSLayoutConstraint:0x1769b680 H:|-(0)-[UIView:0x1769b4b0] (Names: '|':UIView:0x17696bf0 )>",
"<NSLayoutConstraint:0x1769b6c0 H:[UIView:0x1769b4b0]-(0)-| (Names: '|':UIView:0x17696bf0 )>",
"<NSLayoutConstraint:0x17696f70 H:|-(>=0)-[UIView:0x17696bf0] (Names: '|':UIView:0x1768f710 )>",
"<NSLayoutConstraint:0x17696fc0 H:[UIView:0x17696bf0]-(>=0)-| (Names: '|':UIView:0x1768f710 )>",
"<NSAutoresizingMaskLayoutConstraint:0x176a4540 h=-&- v=-&- UIView:0x1768f710.width == SemiNodeFlowLayoutViewCell:0x17690dd0.width>",
"<NSAutoresizingMaskLayoutConstraint:0x175a0050 h=--& v=--& H:[SemiNodeFlowLayoutViewCell:0x17690dd0(0)]>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1769c9b0 H:[UIView:0x1769c740]-(>=0)-| (Names: '|':UIView:0x1769c6e0 )>
<NSLayoutConstraint:0x1769efb0 UIView:0x1769c6e0.centerX == UIView:0x1769b4b0.centerX>
"<NSAutoresizingMaskLayoutConstraint:0x175a0050 h=--& v=--& H:[SemiNodeFlowLayoutViewCell:0x17690dd0(0)]>",
"<NSLayoutConstraint:0x1769f2b0 H:[UIView:0x1769c6e0]-(>=5)-| (Names: '|':UIView:0x1769b4b0 )>"
<NSLayoutConstraint:0x1769f2b0 H:[UIView:0x1769c6e0]-(>=5)-| (Names: '|':UIView:0x1769b4b0 )>
I can prevent these from happening by changing my constraints priority from 1000 to 999, but that has other unintended consequences, too.
Thoughts?
When a cell leaves the screen, its frame is set to CGRectZero. So if i had to guess, one of your constraints doesn't play nicely with a zero size?
-SteveZ
Hmm... many of the constraints say "you must be >= X points from each other" and, of course, CGRectZero would break those constraints. Afaik, isn't the case with UITableViewCell, so I wonder what happens differently. Keep in mind that I'm using a parent/child VC relationship... so, do the views /or VCs need to be unloaded somehow? Perhaps through removeFromParentViewController? I could also remove the constraints manually, but then the problem is cellAttached/cellDetached are called too late - after the frame is set.
cellDetached is called on the next line.
However, there isn't any particular reason that it has to happen first, so i can just a easily swap the two method calls, so that cellDetached occurs before we change the frame.
The same goes for cellAttached.
In fact, i could add a method that would get called before i set the frame giving you an option to listening to either before/after.
That sounds good. I'll try to unload/reload the VCs once you make the changes and see if that makes a difference.
I could use a SR on this sooner than later. Very strange errors from Autolayout engine...
Integralization Adjustments:
(none)
Statistics:
16 rows. Variable counts:
1 -> 2
2 -> 10
3 -> 2
4 -> 2
}: internal error. Cannot find an outgoing row head for incoming head {id: 1430}, which should never happen.'
EDIT: This was caused by a FRC delegate callback modifying auto layout from either 1) at an incorrect time during the main runloop, or 2) not on the main thread.