集合视图单元格的自动布局问题

Question

I am trying to create a somewhat basic layout and am having the classic "Unable to simultaneously satisfy constraints" problem. After an hour on it I cannot track it down.

Here is the layout in interface builder:

Please note that no constraints are being added/modified in code. Everything is happening in IB.

Here is the error message I am getting:

2015-03-07 19:13:33.044 TwitterStats[4326:209207] Unable to simultaneously satisfy constraints.
    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:0x7f888ad8b700 H:[UIImageView:0x7f888ad8ce40(90)]>",
    "<NSLayoutConstraint:0x7f888ad8f910 H:|-(8)-[UIImageView:0x7f888ad8ce40]   (Names: '|':UIView:0x7f888ad8cd70 )>",
    "<NSLayoutConstraint:0x7f888ad8fb40 UIView:0x7f888ad8cd70.trailingMargin == UILabel:0x7f888ad87790'@username'.trailing + 10>",
    "<NSLayoutConstraint:0x7f888ad8fb90 H:[UIImageView:0x7f888ad8ce40]-(14)-[UILabel:0x7f888ad87790'@username']>",
    "<NSAutoresizingMaskLayoutConstraint:0x7f888af29690 h=--& v=--& H:[UIView:0x7f888ad8cd70(50)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7f888ad8b700 H:[UIImageView:0x7f888ad8ce40(90)]>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2015-03-07 19:13:33.045 TwitterStats[4326:209207] Unable to simultaneously satisfy constraints.
    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:0x7f888ad8b210 V:[UIImageView:0x7f888ad8ce40(90)]>",
    "<NSLayoutConstraint:0x7f888ad8f450 V:[UIButton:0x7f888ad8f150'Unfollow'(52)]>",
    "<NSLayoutConstraint:0x7f888ad8f8c0 V:|-(8)-[UIImageView:0x7f888ad8ce40]   (Names: '|':UIView:0x7f888ad8cd70 )>",
    "<NSLayoutConstraint:0x7f888ad8fa00 V:[UIImageView:0x7f888ad8ce40]-(10)-[UITableView:0x7f888b840000]>",
    "<NSLayoutConstraint:0x7f888ad8fc30 V:[UITableView:0x7f888b840000]-(0)-[UIButton:0x7f888ad8f150'Unfollow']>",
    "<NSLayoutConstraint:0x7f888ad8fcd0 V:[UIButton:0x7f888ad8f150'Unfollow']-(0)-|   (Names: '|':UIView:0x7f888ad8cd70 )>",
    "<NSAutoresizingMaskLayoutConstraint:0x7f888af3cb10 h=--& v=--& V:[UIView:0x7f888ad8cd70(50)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7f888ad8b210 V:[UIImageView:0x7f888ad8ce40(90)]>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2015-03-07 19:13:33.073 TwitterStats[4326:209207] Unable to simultaneously satisfy constraints.
    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:0x7f888ad8f450 V:[UIButton:0x7f888ad8f150'Unfollow'(52)]>",
    "<NSLayoutConstraint:0x7f888ad8f8c0 V:|-(8)-[UIImageView:0x7f888ad8ce40]   (Names: '|':UIView:0x7f888ad8cd70 )>",
    "<NSLayoutConstraint:0x7f888ad8fa00 V:[UIImageView:0x7f888ad8ce40]-(10)-[UITableView:0x7f888b840000]>",
    "<NSLayoutConstraint:0x7f888ad8fc30 V:[UITableView:0x7f888b840000]-(0)-[UIButton:0x7f888ad8f150'Unfollow']>",
    "<NSLayoutConstraint:0x7f888ad8fcd0 V:[UIButton:0x7f888ad8f150'Unfollow']-(0)-|   (Names: '|':UIView:0x7f888ad8cd70 )>",
    "<NSAutoresizingMaskLayoutConstraint:0x7f888af3cb10 h=--& v=--& V:[UIView:0x7f888ad8cd70(50)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7f888ad8f450 V:[UIButton:0x7f888ad8f150'Unfollow'(52)]>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2015-03-07 19:13:33.111 TwitterStats[4326:209207] Unable to simultaneously satisfy constraints.
    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:0x7f888ac441e0 H:[UIImageView:0x7f888ac87610(90)]>",
    "<NSLayoutConstraint:0x7f888ac4f8e0 H:|-(8)-[UIImageView:0x7f888ac87610]   (Names: '|':UIView:0x7f888ac7f2c0 )>",
    "<NSLayoutConstraint:0x7f888ac8cd20 UIView:0x7f888ac7f2c0.trailingMargin == UILabel:0x7f888ac52b00'@username'.trailing + 10>",
    "<NSLayoutConstraint:0x7f888ac48b90 H:[UIImageView:0x7f888ac87610]-(14)-[UILabel:0x7f888ac52b00'@username']>",
    "<NSAutoresizingMaskLayoutConstraint:0x7f888af3e030 h=--& v=--& H:[UIView:0x7f888ac7f2c0(50)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7f888ac441e0 H:[UIImageView:0x7f888ac87610(90)]>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2015-03-07 19:13:33.113 TwitterStats[4326:209207] Unable to simultaneously satisfy constraints.
    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:0x7f888ac29530 V:[UIImageView:0x7f888ac87610(90)]>",
    "<NSLayoutConstraint:0x7f888ac41d40 V:[UIButton:0x7f888ac53e90'Unfollow'(52)]>",
    "<NSLayoutConstraint:0x7f888ac4f890 V:|-(8)-[UIImageView:0x7f888ac87610]   (Names: '|':UIView:0x7f888ac7f2c0 )>",
    "<NSLayoutConstraint:0x7f888ac8b790 V:[UIImageView:0x7f888ac87610]-(10)-[UITableView:0x7f888b035400]>",
    "<NSLayoutConstraint:0x7f888ac48c30 V:[UITableView:0x7f888b035400]-(0)-[UIButton:0x7f888ac53e90'Unfollow']>",
    "<NSLayoutConstraint:0x7f888ac8ae40 V:[UIButton:0x7f888ac53e90'Unfollow']-(0)-|   (Names: '|':UIView:0x7f888ac7f2c0 )>",
    "<NSAutoresizingMaskLayoutConstraint:0x7f888af2ba00 h=--& v=--& V:[UIView:0x7f888ac7f2c0(50)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7f888ac29530 V:[UIImageView:0x7f888ac87610(90)]>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2015-03-07 19:13:33.114 TwitterStats[4326:209207] Unable to simultaneously satisfy constraints.
    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:0x7f888ac41d40 V:[UIButton:0x7f888ac53e90'Unfollow'(52)]>",
    "<NSLayoutConstraint:0x7f888ac4f890 V:|-(8)-[UIImageView:0x7f888ac87610]   (Names: '|':UIView:0x7f888ac7f2c0 )>",
    "<NSLayoutConstraint:0x7f888ac8b790 V:[UIImageView:0x7f888ac87610]-(10)-[UITableView:0x7f888b035400]>",
    "<NSLayoutConstraint:0x7f888ac48c30 V:[UITableView:0x7f888b035400]-(0)-[UIButton:0x7f888ac53e90'Unfollow']>",
    "<NSLayoutConstraint:0x7f888ac8ae40 V:[UIButton:0x7f888ac53e90'Unfollow']-(0)-|   (Names: '|':UIView:0x7f888ac7f2c0 )>",
    "<NSAutoresizingMaskLayoutConstraint:0x7f888af2ba00 h=--& v=--& V:[UIView:0x7f888ac7f2c0(50)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7f888ac41d40 V:[UIButton:0x7f888ac53e90'Unfollow'(52)]>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.

The strange thing is this constraint <NSAutoresizingMaskLayoutConstraint:0x7f888af2ba00 h=--& v=--& V:[UIView:0x7f888ac7f2c0(50)]> , I don't get where it's coming from.

Any idea on how to solve these issues?

Answer 1

I had same problem yesterday. The NSAutoresizingMaskLayoutConstraint you mentioned was not the problem. I could not figure out where that constraint comes from, but it seems to be normal for collection view cells.

The problem is that the constraints cannot be satisfied. Take a look at the first set of constraints that are not working:

"<NSLayoutConstraint:0x7f888ad8b700 H:[UIImageView:0x7f888ad8ce40(90)]"
"<NSLayoutConstraint:0x7f888ad8f910 H:|-(8)-[UIImageView:0x7f888ad8ce40]   (Names: '|':UIView:0x7f888ad8cd70 )>"
"<NSLayoutConstraint:0x7f888ad8fb40 UIView:0x7f888ad8cd70.trailingMargin == UILabel:0x7f888ad87790'@username'.trailing + 10>"
"<NSLayoutConstraint:0x7f888ad8fb90 H:[UIImageView:0x7f888ad8ce40]-(14)-[UILabel:0x7f888ad87790'@username']>"

You have 8 points from the left edge to the image view. The image view is 90 points wide. You have 14 points from the image view to the username. Then the username is constrained to the trailing margin with 10 points space.

Username is a UILabel and has intrinsic size. Suppose that for a given user it required 40 points to display the username. Your constraints would result in a screen width of 8 + 90 + 14 + 40 + 10 = 162. That would be a very narrow screen! These constraints cannot be satisfied.

The thing to do here is remove this trailing constraint:

"<NSLayoutConstraint:0x7f888ad8fb40 UIView:0x7f888ad8cd70.trailingMargin == UILabel:0x7f888ad87790'@username'.trailing + 10>"

If you are really concerned that the username could be too long, you could try keeping this constraint, but changing it from EQUALS 10 to GREATER THAN OR EQUAL to 10.

Answer 2

I had a similar problem with a UICollectionView in a Storyboard.

The cause for this error is the size of the contentView of the CollectionViewCell. It uses the default size which is (50.0, 50.0). This might be an InterfaceBuilder-Bug.

A fix is to change the priority for your imageView.width (90) and the buttons width (52) to 999.